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Assessing intertidal marine non-indigenous species in Canadian ports Choi, Francis Ming Pong 2011

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ASSESSING INTERTIDAL MARINE NON-INDIGENOUS SPECIES IN CANADIAN PORTS by Francis Ming Pong Choi B.Sc., University of British Columbia, 2007  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in The Faculty of Graduate Studies (Oceanography)  THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) August 2011 © Francis Ming Pong Choi, 2011       ABSTRACT The establishment of non-indigenous species in natural ecosystems is a growing concern at global, national, and regional scales. Over 100 known marine non-indigenous species (NIS) are found along the Pacific and Atlantic coasts of Canada. It is widely believed that commercial shipping activities associated with international ports (e.g. ballast water discharge, hull fouling) could expose native communities to a variety of NIS. Thus, harbours are recognized as critical entry points for NIS and, pending establishment, can serve as invasion hubs for secondary dispersal vectors (e.g. recreational boats). The aim of this study was to characterize intertidal NIS distributions among ports on the Pacific and Atlantic coasts of Canada and to determine if commercial shipping activities (ballast water discharge, vessel arrivals) can be directly linked to the observed patterns of established NIS. Sixteen major international ports in Canada were surveyed for species composition and abiotic conditions, including both environmental and anthropogenic factors. Species diversity for both NIS and native species were found to be significantly different between the Pacific and the Atlantic intertidal communities. Although both NIS and native species had higher diversity on the Pacific coast, the Invasion index, a novel measurement of the degree of invasion developed in this thesis, demonstrated that the Atlantic coast was actually more invaded by NIS than the Pacific. No direct link was found between commercial shipping activities and the distribution patterns of established intertidal NIS in Canadian ports. Instead, NIS distributions were found to be strongly related to salinity, sediment type, human population, aquaculture and latitude on the Pacific coast and human disturbance at docks, latitude and salinity on the Atlantic coast. In contrast to what was previously suggested, these results demonstrated that ballast water discharge and vessel arrival frequency were not detected as the main variables towards NIS  ii     establishment success. However, this study highlighted the importance of environmental conditions and local anthropogenic vectors in the establishment of NIS in new regions. Future research in conservation and management of invaded communities should include environmental conditions and the risk posed by anthropogenic activities, in addition to commercial shipping, when characterizing invasion dynamics.  iii     TABLE OF CONTENTS ABSTRACT .................................................................................................................................................. ii  TABLE OF CONTENTS ............................................................................................................................. iv  LIST OF TABLES ....................................................................................................................................... vi  LIST OF FIGURES ..................................................................................................................................... vii  LIST OF ABBREBIATIONS AND SYMBOLS ......................................................................................... ix  ACKNOWLEDGEMENTS ......................................................................................................................... xi  DEDICATION ............................................................................................................................................ xii  1   INTRODUCTION ................................................................................................................................. 1  1.1   Biological Invasions ...................................................................................................................... 1   1.2   Biological Invasion Impacts .......................................................................................................... 3   1.3   Biological Invasions in Aquatic Ecosystems ................................................................................ 6   1.4   Anthropogenic Vectors in Aquatic Invasions .............................................................................12   1.5   Commercial History of Canadian Ports.......................................................................................15   1.6   Thesis Objectives ........................................................................................................................18   2  EXAMINING INTERTIDAL NIS PATTERNS AMONG PACIFIC AND ATLANTIC CANADIAN PORT COMMUNITIES .......................................................................................................21  2.1   Introduction .................................................................................................................................21   2.2   Methods and Materials ................................................................................................................25   2.3   Results .........................................................................................................................................33   2.4   Discussion ...................................................................................................................................44   2.5   Conclusions .................................................................................................................................54   3  EXAMINING ENVIRONMENTAL AND ANTHROPOGENIC VARIABLES ASSOCIATED WITH INTERTIDAL NIS PATTERNS IN PACIFIC AND ATLANTIC CANADIAN PORT COMMUNITIES .........................................................................................................................................57      3.1   Introduction .................................................................................................................................57   3.2   Materials and Methods ................................................................................................................61  iv   4   5   3.3   Results .........................................................................................................................................69   3.4   Discussion ...................................................................................................................................76   3.5   Conclusions .................................................................................................................................85   GENERAL DISCUSSION ..................................................................................................................87  4.1   Species Distribution ....................................................................................................................87   4.2   Propagule Pressure from Commercial Shipping .........................................................................90   CONCLUSION ...................................................................................................................................93   REFERENCES ............................................................................................................................................95  APPENDICES.......................................................................................................................................... 113  Appendix A: The Invasion Index () .................................................................................................. 113  Appendix B: List of Non-indigenous Species ...................................................................................... 117              v     LIST OF TABLES Table 2-1. List of ports sampled on the Canadian Pacific and Atlantic coasts ...........................................28  Table 2-2. List of non-indigenous species that are potentially introduced by ballast water discharge ......33  Table 2-3. Comparing nested Welch ANOVA of average indices between Pacific and Atlantic coast of Canada. Significant differences between coasts (F test, p-value < 0.05) are indicated by * ......................39  Table 3-1. List of abiotic variables used to correlate with NIS establishment success ..............................63  Table 3-2. Significant correlations between abiotic variables and community compositions in intertidal communities of Pacific Canadian ports .......................................................................................................70  Table 3-3. Significant correlations between abiotic variables and community composition in intertidal communities of Atlantic Canadian ports .....................................................................................................70        vi     LIST OF FIGURES Figure 1-1. Proposed marine invasion pathway (Colautti & MacIsaac, 2004). Stages and filters that determines successful establishment for NIS ..............................................................................................11  Figure 2-1. Study sites from the Canadian intertidal survey. White dots represent the 16 international ports surveyed on the Pacific a) and Atlantic b) coasts of Canada .............................................................27  Figure 2-2. Biological diversity index of the Pacific and Atlantic coast of Canada separated by ports. Species richness index of the Pacific a) and Atlantic b), Shannon-Wiener (S-W) diversity index of the Pacific c) and Atlantic d) coast (n = 6 sites per port) and Simpson’s diversity index of the Pacific e) and Atlantic f) coast (n = 6 sites per port). White and black bars represent the native and non-indigenous species (NIS) diversity for each port, respectively. Dotted line represents the average coastal native species diversity, while the black solid line represents the average coastal NIS diversity for each coast. Letters inside each bar represent Tukey’s HSD test results. Ports with different letters represent significant differences in diversity index ....................................................................................................36  Figure 2-3. Invasion Index of the Pacific a) and Atlantic b) coast, separated by ports (n=6 sites per port). The Invasion index for each port is shown above its respected bars. Letters inside each bar represent Tukey’s HSD test results with the Invasion index. Ports with the different letters represent significant differences in Invasion index. Solid lines represent the mean of the Invasion Index (n=8 ports per coast)  .....................................................................................................................................................................38  Figure 2-4. Cluster analysis from Pacific coast species richness dataset. Intertidal sites are grouped together based on the similarities in species richness. Black solid lines on linkage tree represent significant differences in grouping. Faded lines represent no significant differences in grouping .............42  Figure 2-5. Cluster analysis from Atlantic coast species richness dataset. Intertidal sites are grouped together based on the similarities in species richness. Black solid lines on linkage tree represent significant differences in grouping. Faded lines represent no significant differences in grouping .............43  Figure 2-6. Positive trends of native diversity to NIS diversity of both Pacific and Atlantic coast. Diversity measurement is represented through species richness. ................................................................50  Figure 3-1. The distributions of significant abiotic variables with established intertidal NIS in Pacific ports. These include water retention from sediments, latitude, sea surface salinity, human population and aquaculture effects ......................................................................................................................................72  Figure 3-2. The distributions of abiotic variables that were measured in this study but did not show correlation with established intertidal NIS in Pacific ports. These include dock effects, intertidal slope height, ballast water discharge, vessel arrivals and sea surface temperature ..............................................73  Figure 3-3. The distribution of significant abiotic variations with established intertidal NIS in Atlantic ports. This includes latitude, sea surface salinity, sea surface temperature and dock effects .....................74  Figure 3-4. The distributions of abiotic variables that were measured in this study but did not show correlation with established intertidal NIS in Atlantic ports. These include ballast water discharge, vessel arrivals, human population, sediments and intertidal slope height .............................................................75  vii     Figure A-1. The Invasion index model, where N = 100. Reference point is specified at 0.25. When the index is above this reference point, invasion effect becomes progressively greater towards the community. When the index is lower than this reference point, invasion effect are suggested to be not apparent towards the community ............................................................................................................. 115   viii     LIST OF ABBREBIATIONS AND SYMBOLS AIDS  Acquired Immune Deficiency Syndrome  ANOVA  Analysis of Variance  BC  British Columbia  BEST  Bio-Envir Stepwise Test  BNIS  Ballast water discharge-related Non-indigenous Species  CAISN  Canadian Aquatic Invasion Species Network  D  Simpson`s Diversity Index  DD  Decimal Degree    Invasion index  GDP  Gross Domestic Product  GIS  Geographic Information System  GPS  Global Positioning System  H`  Shannon-Wiener Diversity Index  HIV  Human Immunodeficiency Virus  HSD  Honestly Significant Difference (Tukey HSD test)  kt  Kilotonne  m  Metre  ml  Millilitre  MOE  Mid Ocean Exchange  NIS  Non-indigenous Species  NOAA  National Oceanic and Atmospheric Administration  ᵒC  Degree Celsius  ppt  Parts per Thousand  PRIMER  Plymouth Routines in Multivariate Ecological Research  ix     PVC  Polyvinyl Chloride  SARS  Severe Acute Respiratory Syndrome  SAS  Statistical Analysis Software  SD  Standard Deviation  SIMPER  Similarity Percentage Routine  SoG  Strait of Georgia  SWFSC  Southwestern Fisheries Science Center  UBC  University of British Columbia  UK  The United Kingdom  USA/US  The United of States of America  x     ACKNOWLEDGEMENTS I am extremely grateful for the support provided by my supervisors: Evgeny Pakhomov and Thomas Therriault. I am also thankful for the encouragements and assistance provided by my committee member Christopher Harley. Special thanks to Cathryn Clarke Murray, Megan Mach and Jason McAlister for the comments, suggestions and encouragement provided throughout this research study. Additional thanks to all the sampling team members: Heidi Gartner, Lu Guan, Christina Simkanin, and Matthew Thompson (Canadian Aquatic Invasive Species Network (CAISN) west coast sampling team), Chris McKindsey, Olivia Lacasse, Julie Sperl, and Katie Sanford (CAISN east coast sampling team) and Trampus Goodman, Emily Tang, Yasha Podeswa, Angela Stevenson, and Jessica Yu (UBC sample processing team). Taxonomic expertise was provided by John Chapman and James Carlton. Transport Canada vessel traffic data was provided by Sarah Bailey. This research study was conducted as a part of the CAISN funded by the Natural Sciences and Engineering Research Council of Canada (NSERC). Funding for this research was provided by NSERC, Fisheries and Oceans Canada and the University of British Columbia. Last but not least, special thanks to all my friends (e.g. Tony Leung, Jennifer Duong, etc.) and family (Jethro Choi, Carmen Choi and Angela Choi) for the unconditional support and motivation provided for the past few research years.             xi     DEDICATION This is dedicated to all of those who believed in me through thick and thin. It is your support that got me to where I am today and it is your support that I will continue to strive for excellence.  xii     1  INTRODUCTION  1.1 Biological Invasions Biological introductions are events where species are introduced into new environments outside of their native and historic habitat range (Elton, 1958; di Castri, 1989; Simberloff, 1996; Williamson, 1996; Bright, 1999; Lowe et al., 2000; Mack et al., 2000; Davis, 2006; Levine, 2008). These introductions, intentional or accidental, usually are mediated by humans (Elton, 1958; di Castri, 1989; Heywood, 1989; Lowe et al., 2000; Levine, 2008). In rare cases, species can be naturally introduced through a sporadic event via natural vectors to regions outside its current geographic range by overcoming formidable natural dispersal barriers (e.g. mountain ranges and oceans) (Elton, 1958; di Castri, 1989; Williamson, 1996; Mack et al., 2000; Levine, 2008). This is different from range expansion, where species have the ability to move beyond its geographic range gradually through time due to evolution or interspecies competition for resources as there is no barrier to dispersal in range expansion. Species that successfully settle and establish in new habitats through biological introductions are referred to as non-indigenous species (NIS), the term used in this thesis (Richardson et al., 2000; Ruiz et al., 2000a; Kolar & Lodge, 2001). The term biological invasion is used to describe a more specific biological introduction event. Biological invasions occur when species that are introduced into new habitats have a significant negative impact on native species composition (biodiversity), native ecosystem functions, world economies, or human health (Elton, 1958; Williamson, 1996; Mack et al., 2000; Richardson et al., 2000; Ruiz et al., 2000a; Sax et al., 2005; Davis, 2006; Perrings et al., 2010). The terms invasive species and NIS have been used interchangeably when in fact, invasive species are a special subset of NIS that represent true biological invasions (Richardson et al., 2000; Ruiz et al., 2000a; Kolar & Lodge, 2001; Rilov & Crooks, 2009). 1     Biological invasions and the successful introduction of NIS to new habitats provides an unprecedented opportunity for ecologists to study the processes that structure the distribution and abundance of native and non-indigenous species, which includes community associations and evolutionary relationships (Cassey, 2005; Levine, 2008). The opportunity and fascination to study biological invasions date back to Charles Darwin in 1860 (Williamson, 1996). Even though he observed dozens of examples of biological introductions throughout his travels, it is interesting to note that he never described NIS as pests. Since many of the introduced plants Darwin observed were well integrated and common throughout islands with native species, he noted that some NIS could co-exist with native species without tremendous damage to native ecosystems and human society, while others were noted to have negative impacts (Williamson, 1996; Richardson & Pysek, 2008). Although Darwin noted the presence of NIS on his voyages, Charles Elton, who initiated global interest and understanding of biological invasions, is acknowledged as the father of invasion biology (Williamson, 1996; Davis et al., 2001). The foundation of invasion ecology was established by Elton’s (1958) book “The Ecology of Invasions by Animals and Plants”. It introduced concepts of biological invasions that many early invasion studies examined, concepts including dispersal and spread of non-indigenous organisms (including invasibility of islands), biodiversity impacts (diversity-stability or diversityinvasibility relationships), role of disturbance (predation, competition, and facilitation by NIS), and enemy release (May & MacArthur, 1972; Williamson, 1996; Levine & D’Antonio, 1999; Colautti et al., 2004; Pysek, 2007; Richardson and Pysek, 2008). Over the last century, invasion ecology has moved from examining these classic concepts of invasions introduced by Elton to focusing on new, emerging biological invasion themes that contribute to conservation and applied ecology (Levine & D’Antonio, 1999; Davis et al., 2001; Richardson and Pysek, 2008). These themes have transformed biological invasion research into a 2     multi-facet ecological discipline (Levine & D’Antonio, 1999; Richardson and Pysek, 2008; Rilov & Crooks, 2009). Not only does invasion ecology study specific aspects of NIS, the modern themes of invasion ecology also incorporate different fundamental processes in populations, communities, and ecosystems across different species and scales (Williamson, 1996; Richardson and Pysek, 2008; Rilov & Crooks, 2009). Population ecologists study biological invasions to understand changes in abundance of NIS starting from the establishment stage (Rilov & Crooks, 2009). Community ecologists study the interactions between established NIS and native species, including invasion effects on native diversity (Meiners et al., 2004; Eppstein & Molofsky, 2007; Shurin et al., 2007). Finally, conservation ecologists study invasions to devise strategies for conservation, ecological restoration, and pest management (Rilov & Crooks, 2009). The combination of classic concepts and modern themes of biological invasions have led to a complicated but multi-facet discipline: invasion ecology.  1.2 Biological Invasion Impacts One of the main objectives of biological invasion ecology is to study its impacts. Biological invasions are a problem that can have significant impacts on regional, national, and global ecosystems (Vitousek et al., 1997; Sala et al., 2000), resulting in ecological, economic, and societal damages (Wilcove et al., 1998; Sala et al., 2000; Davis et al., 2001). Ecological impacts such as regional mass extinctions often have been linked to biological invasions (Sala et al., 2000; Levine, 2008). These events (regional extinctions) have created a common perception that biological invasions are the second greatest threat to biodiversity after habitat destruction (Vitousek et al., 1996; Dafforn et al., 2009). Decreased biodiversity caused by biological invasions could be in the form of predation, competition, and habitat alteration by NIS (Case, 1990; Chamber et al., 1993; Mack et al., 2000; Levine, 2008; Dafforn et a., 2009). An infamous case of biodiversity loss by invasive species predation is the invasion of the brown tree snake 3     (Boiga irregularis) in Guam; because Guam is an island without snakes or similar top predators, native species were extremely vulnerable due to a lack of natural defences. This invasion resulted in the extinction of three-fourths of native birds, and two-thirds of native bats (Rodda et al., 1999; Lowe, 2000; Wiles et al., 2003; Levine, 2008). In addition, a significant reduction in small terrestrial species also occurred. Only five species of native lizards and small mammals currently have stable populations in Guam (Rodda & Fritts, 1992; Levine, 2008). A common example of biodiversity loss by invasion competition and habitat alteration involves the Caulerpa algae species (Caulerpa taxifolia, Caulerpa racemosa), which can rapidly grow on the seabed. These algae alter the benthic habitat by overgrowing the seabed and disrupting native species by competing for sunlight and other resources (Meinesz et al., 1993; Lowe, 2000; Piazzi et al., 2001, Meinesz et al., 2001). By 2001, over 13100 hectares of the Mediterranean coastline have been invaded by Caulerpa species. This invasion spanned over 103 independent areas across six countries (Meinesz et al., 2001) Another study showed a decrease in native species richness by 75% in the first six months of Caulerpa sp. introduction (Piazzi et al., 2001). Biological invasion impacts on biodiversity also have been observed in aquatic systems in North America, where approximately 150 marine and freshwater species extinctions have been attributed to invasive species (Ricciardi & Rasmussen, 1999). From an economic perspective, the impacts of biological invasions can cause significant problems (Pimentel et al., 2000; Pimentel, 2002; Colautti et al., 2006). Around the world, countries lose billions of dollars annually due to high risk invasive species, also called pests or nuisance species (Pimentel et al., 2000; Colautti et al., 2006; Levine, 2008; Dafforn et al., 2009). These pests cause damage to agriculture crops, natural resources, and urban services (Pimentel, 2002; Singh & Kaur, 2002; Colautti et al., 2006; Perrings et al., 2010). Australia, Brazil, India, New Zealand, South Africa, the UK, and the USA estimated a total of $314 billion per year in 4     damage and control costs for invasive species (Pimentel, 2002; Perrings et al. 2010). The most common economic damage created by invasive species among countries was agricultural damage. The major culprits causing this damage were invasive plant pathogens, weeds, and invertebrates. Noteworthy cases of agricultural GDP rate decline due to biological invasions include Australia (49%), Brazil (112%), India (78%), South Africa (96%), and the USA (53%) (Perrings et al., 2010). The decline in agricultural GDP can result in catastrophic events. For example, the Bengal famine of 1943, when approximately two million people died from starvation (Singh & Kaur, 2002), was caused by the invasion of the fungus, Helminthosporium, in rice paddies. Biological invasions also can have tremendous impacts on human society (Perrings et al., 2010b). As has already been mentioned, human starvation can result from a ripple effect of agricultural decline due to biological invasions (Singh & Kaur, 2002). Other notable direct impacts of biological invasions to human society are the spreading of pathogenic diseases (Pimentel, 2002). They can spread worldwide through human hosts; for example, HIV, tuberculosis, SARS, influenza, and the common cold are spread this way (Kim, 2002; Pimentel, et al., 2002; Perrings et al., 2010b). They also can be transported around the world through other vectors; for example, malaria and West Nile virus can be transmitted through mosquitoes (Kim, 2002) or cholera can be transported through ballast water tanks, which resulted in the death of 10,000 people in Peru during 1991 (Kolar & Lodge, 2001; Kim, 2002; Pimentel, et al., 2002). The spread of HIV globally has infected 36.1 million people as of 2000, with the majority of cases located in Africa and India (Pimentel et al., 2002). These diseases not only affect human health, but also the economies of these countries. For example, USA spends close to $20 billion dollars a year to prevent and treat HIV/AIDS (Pimentel et al., 2002; Perrings et al., 2010b).  5     In addition to the negative impacts mentioned above, some biological introductions of NIS have resulted in positive economic impacts. These NIS often are used in agriculture resulting in positive economic yield. For example, in British Columbia, six of the eight shellfish species introduced to Canada from Asia were for aquaculture. These shellfish, especially the Pacific oyster (Crassostrea gigas), have displaced most of the native Olympia oysters (Ostrea conchaphila) in the Strait of Georgia. Although harmful towards the biodiversity in the region, these six species are the major species for the BC aquaculture industry. In 2008, $15.7 million of revenue was generated from these non-indigenous shellfish (BC Ministry of Environment, 2008). Biological, economic, and social impacts from biological introductions largely are unpredictable and can be highly species specific (Carlton & Geller, 1993; Williamson, 1996; Williamson, 2010). For example, some NIS can settle, establish, and integrate within ecosystems without any apparent negative impacts (Simberloff, 1981), while others can completely change the dynamic of an ecosystem (Sala et al., 2000; Levine, 2008). Even the same NIS introduced to different environments can have significantly different impacts (Carlton & Geller, 1993; Ruiz et al., 2000a; Williamson, 2010). These uncertainties in impacts by biological invasions are often termed “ecological roulette” (Carlton & Geller, 1993). Current invasion scientists pushed for better understanding of the processes and dynamics of biological invasions to avoid ecological roulette and predict impacts of various NIS (Williamson, 1996; Ruiz et al., 2000a).  1.3 Biological Invasions in Aquatic Ecosystems Aquatic ecosystems (freshwater, marine and estuarine) are considered to be among the most invaded ecosystems in the world (Moyle, 1999). The rationale for the high prevalence of invasions in these ecosystems is that aquatic invaders have the ability to be moved easily around the world largely due to modernization of international trade (Carlton and Geller, 1993; Ruiz et 6     al., 1997; Cohen, 1998; Bright, 1999; Kolar & Lodge, 2001; Bax et al., 2003; Minton et al., 2005; Johnston et al., 2009). Currently, over 10,000 species are thought to be transported around the world at any given time (Bax et al., 2003). These invaders have established in vulnerable environments, resulting in catastrophic ecological changes. One example is the 1954 invasion of Nile perch, Lates niloticus into Lake Victoria, the largest lake in Africa. This invasion resulted in substantial loss of native fish species (Lowes et al., 2000); more than 200 native fish have become extinct in Lake Victoria since the introduction of Nile perch (Reinthal & Kling, 1997; Lowes et al., 2000; Kolar & Lodge, 2001). Similarly, in North America, over 170 NIS were found in the Great Lakes region and over 300 non-indigenous invertebrates were reported from marine and estuarine ecosystems across the continent (Ricciardi & Rasmussen, 1999; Ruiz et al., 2000a; Ricciardi, 2001; Holeck et al., 2004). Recently, three prominent aquatic invasive species have established in Canada; the spiny water flea (Bythotrephes longimanus), the zebra mussel (Dreissena polymorpha), and the European green crab (Carcinus maenas) (Jamieson et al., 1998; Colautti et al., 2006). These species have impacted aquatic systems either by displacing native species or by damaging infrastructure. The spiny water flea and the zebra mussel have heavily impacted ecosystems throughout the Great Lakes basin. Native phytoplankton and zooplankton species are being displaced by these species. The spiny water flea, for example, is a devastating predator to smaller native plankton in the Great Lakes. Not only does this invader flourish under these conditions, their long spines make them unfavourable prey for larger Great Lakes native species. As a result, their population and predatory effects extend throughout the Great Lakes without any top down control by native species. The feeding efficiency of zebra mussels has negatively impacted the overall abundance of all plankton in the Great Lakes. Each zebra mussel can filter and process up to 4 litres of water a day (OTA, 1993). This feeding ability, in combination with large zebra 7     mussel populations in the Great Lakes, has resulted in rapid clearance, drastically reducing algae and plankton populations. Native plankton and algae are the fundamental food resource for the Great Lakes food web (Ricciardi & Rasmussen, 1999) and the depletion of plankton due to these invasive species has resulted in native fish starvation through a negative bottom-up effect in the system (Griffiths et al., 1991). In addition to ecological impacts, zebra mussels have infested water intake pipes for drinking water, electric generation, and other industrial facilities on the Great Lakes, thereby lowering the efficiency of these facilities (OTA, 1993). In 1989, Monroe, Michigan lost its water supply for three days due to a massive infestation of zebra mussels (Griffiths et al., 1991). Since then, millions of dollars have been invested by both the government and private industrial sector to prevent and treat zebra mussel infestations (Griffiths et al., 1991; OTA, 1993). Zebra mussels were estimated to have an approximate total economic impact of $5 billion to the Great Lakes region alone (OTA, 1993). As for marine ecosystems in North America, the recent invasion of the European green crab (Carinus maenas) has resulted in native biodiversity loss and economic damages in coastal regions (Cohen et al., 1995; Jamieson et al., 1998; Colautti et al., 2006). The European green crab is an extremely aggressive species that feeds on a wide array of prey, including various bivalves, gastropods, and crustaceans including other crab species (Elner, 1981; Juanes, 1992; Cohen et al., 1995; Grosholz & Ruiz, 1996; Jamieson et al., 1998). On both the Atlantic and Pacific coasts of North America, declines in native crustacean and bivalve populations have been associated with predation by European green crab (Cohen et al., 1995; Grosholz & Ruiz, 1996; Jamieson et al., 1999). The decline in native species includes aquaculture species as well (Glude, 1955; Floyd & Williams, 2004). A field experiment at an aquaculture site in Nova Scotia linked European green crab abundance to a 50% decline in the abundance of soft-shell clam, Mya arenaria (Floyd & Williams, 2004). One reason for the prevalence of these invasive crabs is that 8     they have exceptionally broad environmental tolerances (Crothers, 1967; Rasmussen, 1973; Grosholz & Ruiz, 1996); including withstanding near freshwater and freezing (near 0 oC) aquatic environments (Beukema, 1991). As a consequence, green crab can be found in various intertidal habitats, from open sand and mudflats to shell, cobble, and algal-dominated intertidal sites (Ropes, 1988; Griffiths et al., 1992; Thiel & Dernedde, 1994; Jamieson et al., 1998). This degree of tolerance of the European green crab allows this species to be widespread and difficult to manage, control, and eradicate (Grosholz & Ruiz, 1996; Jamieson et al., 1998). As these examples have demonstrated the potential negative impacts of a particular invasive species, considerably less is known about the general trends of introduction, establishment, integration, and consequences of biological invasions in marine ecosystems (Colautti & MacIsaac, 2004; Johnston et al., 2009). Only a small percentage of published biological invasion studies have focused on marine ecosystems (Parker et al., 1999; Johnston et al., 2009). The general trends of introduction, establishment, integration, and consequences of NIS can be described using a conceptual flowchart of invasions called the “invasion pathway” (Moyle & Light, 1996; Colautti & MacIsaac, 2004). The invasion pathway describes multiple stages and filters that NIS need to pass for successful establishment in new environments (Figure 1-1; Williamson, 1996; Kolar & Lodge, 2001; Leung et al., 2002; Colautti et al., 2004; Colautti & MacIsaac, 2004). Any establishment of NIS begins with initial dispersal (Stages 1 and 2): e.g. NIS needed to be taken up (Stage 1) and transported over natural barriers to dispersal and released into new environments (Stage 2). Initial dispersal may come in the form of natural (wind, currents, animals hitchhiking, etc.) or human-mediated (shipping, aquaculture, aquarium trade, etc) (Williamson, 1996; Colautti & MacIsaac, 2004). Non-indigenous species must survive the multiple stresses in Stages 1 and 2 (transport and release survival filter) to successfully move to the next stage of the invasion pathway: establishment (Stage 3) (Wonham et al., 2001; 9     Minchin & Gollasch, 2003; Johnston et al., 2009). Establishment requires NIS to survive the ecological resistance from the new receiving environment (environment and community suitability filter) to settle and have the ability for reproduction and recruitment (Williamson et al., 1986; Blackburn & Duncan, 2001). Filters that prevent establishment can be a) environmental, such as temperature or salinity suitability, b) biological, such as predation and competition, and c) anthropogenic, such as human disturbance and invasion eradication (Levine, 2008). If NIS are able to pass the environmental and community suitability filters, the final stages of the invasion pathway are the different mechanisms of integration (Colautti & MacIsaac, 2004). Non-indigenous species can integrate into a new environment via three routes: 1) by being widespread to all new habitats (Stage 4a), 2) by being locally abundant in a specific contained region (Stage 4b), or 3) by being both locally abundant and regionally widespread (Stage 5).  10     Figure 1-1. Proposed marine invasion pathway (Colautti & MacIsaac, 2004). Stages and filters that determines successful establishment for NIS   The filters described in the invasion pathway are usually effective at preventing the establishment of NIS (Colautti & MacIsaac, 2004). Most NIS, when introduced, will fail to survive or be filtered out of the invasion process at one of the five stages and therefore are not able to become established and integrated in a new environment (Case, 1990; Moyle & Light, 1996). Only a small fraction of introduced organisms will survive and persist through all stages (Williamson & Fitter, 1996). Some have suggested a “tens rule” to describe the probability of successful establishment for NIS (Williamson, 1996; Williamson & Fitter, 1996). This “rule” suggests that among the initial suite of species transported to new environments, only 10% of these species will be introduced. Of the 10% introduced, only 10% of those will become established and only 10% of the established species will become integrated and negatively 11     impact their new environment, becoming invasive species. Thus, according to the “tens rule”, only 0.01% of introduced NIS are proposed to become invasive. Combining the invasion pathway and the “tens rule”, the initial dispersal stages (Stage 1 and Stage 2) should be the most important stages in the invasion pathway (Williamson & Fitter, 1996b; Webb et al., 2002). This is because the initial dispersal stages determine the specific species that are introduced to the new environment (Webb et al., 2002; Johnston et al., 2009). In addition, those stages determine the abundance of each NIS transported and released into the new environment (this is called propagule pressure, which will be discussed later) (Williamson & Fitter, 1996b). According to the “tens rule”, the abundance of NIS from the initial dispersal event will ultimately determine the likelihood of the NIS to establish in the new environment (Williamson & Fitter, 1996a; Williamson & Fitter, 1996b). The greater this initial abundance is, the greater the likelihood of a specific NIS establishing in the new environment. Although the importance of the initial dispersal stages has been discussed, meta-analyses have shown that most biological invasion studies focus on the latter stages of the invasion pathway (Stages 3-5) (Webb et al., 2002; Johnston, et al., 2009). Only 4.8% of the studies examined the processes and modes of initial dispersal (Puth & Post, 2005). Many recent and ongoing studies on marine invasions have suggested additional research towards better understanding and characterizing Stages 1 and 2 of the invasion pathway is needed to ultimately to fill gaps between initial dispersal and full integration of marine NIS to new regions (Ruiz et al., 2000a; Puth & Post, 2005; Colautti et al., 2006).  1.4 Anthropogenic Vectors in Aquatic Invasions One of the main components of initial dispersal is the vectors or the means of transport used by NIS to move outside their native environment across natural dispersal barriers into new environments (Elton, 1958; Levine, 2008). In the past, natural vectors such as wind, currents, 12     and hitchhiking animals played an important role in NIS dispersal and introduction (Elton, 1958; di Castri, 1989). Under natural dispersal mechanisms, introduction of NIS to new environments is rare and NIS integration to new environments often occurred over long time scales (Elton, 1958; di Castri, 1989). More recently, anthropogenic transport vectors have played an increasingly important role in increasing NIS introduction and, hypothetically, NIS establishment (Levine, 2008). Anthropogenic vectors for aquatic invasions include commercial shipping (hull fouling, ballast water and sediment, sea-chests), canals, aquaculture, and aquarium/seafood trade (Williamson et al., 1986; Carlton, 1987; Carlton & Geller, 1993; Ruiz et al., 2000a). Among anthropogenic vectors, commercial shipping vectors are considered the primary vectors for aquatic NIS introductions, which make ports and harbours, destinations of most commercial shipping activities, among the most vulnerable environments to aquatic biological invasions (Allen, 1953; Williamson et al., 1986; Carlton, 1987; Ruiz et al., 2000a; Coutts et al., 2003). These vectors became ever more prominent because of the globalization of trade that rapidly changed the magnitude of commercial shipping (Carlton, 1987; Ruiz et al., 2000a; Kolar & Lodge, 2001). International shipping has increased in frequency, size, speed, and distance traveled, resulting in more species being transported around the world and released into new environments (Allen, 1953; Ruiz et al., 2000a; Kolar & Lodge, 2001; Bax et al., 2003). At any given time, an estimated 10,000 species are being transported around the world via the commercial shipping (Bax et al., 2003). In North America alone, over 300 established NIS are suspected to have been mediated by commercial shipping (Ruiz et al., 2000a). This includes 50% of the NIS found in coastal environments (Ruiz et al., 2000a) and 67% of the NIS recorded in the Great Lakes (Grigorovich et al., 2003); making commercial shipping vectors the most significant vectors for introductions into the Great Lakes (Holeck et al., 2004; Bailey et al., 2005; Duggan et al., 2005; Ricciardi, 2006; Kelly et al., 2009). 13     Commercial shipping activities also have been hypothesized as the main influence for NIS establishment success. This is because of the sheer magnitude of propagule pressure from these vectors (Carlton, 1987; Ruiz et al., 2000a; Kolar & Lodge, 2001). Propagule pressure is a measure of the number of NIS released in an area (Ruiz et al., 2000a; Johnston et al., 2009) and a surrogate for NIS establishment (Johnston et al., 2009). It is commonly believed that the magnitude of propagule pressure released by commercial shipping activities have the ability to overcome all survival filters for NIS to successfully settle, establish, and integrate into the new system (Carlton, 1987; Carlton & Geller, 1993; Ruiz et al., 2000a) . This hypothesis, the propagule supply hypothesis, proposed that the greater the potential NIS introduction, the higher the probability of NIS to settle and establish in the new ecosystem. Both the propagule supply hypothesis and the “tens rule” suggested the initial propagule release (vector strength) is important towards the establishment probability of NIS. One such specific shipping vector that has been discussed recently is ballast water. Ballast water is water taken up by vessels into ballast tanks at the departure port to ensure stability of the vessel during the voyage (Cohen, 1998). Once at the destination port, ballast water is discharged (often in high volumes) to counter-adjust for changes in cargo weight (Cohen, 1998; Bax et al., 2003; Minton et al., 2005). Invasion studies have hypothesized that the high discharge of ballast water could be associated with high propagule pressure (Ostenfeld, 1908; Carlton, 1985; Levings et al., 1998; Harvey et al., 1999; Piercey et al., 2000; Ruiz et al., 2000a; Levings et al., 2002; Carlton & Ruiz, 2003). Past studies have found living organisms within ballast tanks at arrival ports including: polychaetes, copepods, amphipods, bivalves, and crustacean larvae (Williams et al., 1977; Carlton, 1987; Hallegraeff & Bolch, 1991; Subba Rao et al., 1994; Humphry, 2008; Briski, 2011). These findings suggest that when ballast water is discharged into new environments so are the living organisms in the ballast tanks. Ballast water discharge as a NIS vector has been 14     considered in Australia and North America as the most effective method for releasing NIS to new environments, primarily due to globalization of commercial shipping that has resulted in high volumes of ballast water being dispensed to a variety of aquatic ecosystems every year (Harvey et al., 1999; Levings et al., 1998; Ruiz et al., 2000a; Holeck et al., 2004; Bailey et al., 2005; Duggan et al., 2005; Ricciardi, 2006; Kelly et al., 2009). Therefore, it has been assumed that as ballast water discharge increases in volume, so does propagule pressure. In 1995, the annual global ballast water discharge was estimated at over 10 billion tonnes and it was expected to increase annually (Rigby et al., 1995). Global propagule pressure by ballast water discharge is expected to promote and increase the efficiency of NIS establishment in new port environments. A few studies have already attempted to examine this relationship but no concrete results were found for marine ecosystems (Levings et al., 2002; Johnston et al., 2009).  1.5 Commercial History of Canadian Ports Since commercial shipping is commonly acknowledged as the major vector for aquatic invasions, ports and harbours around the world are assumed to be among the most vulnerable to invasions (Carlton, 1987; Ruiz et al., 2000a). Canada has acknowledged that port communities are potentially threatened by incoming NIS through ballast water. In 2006, Transport Canada initiated mandatory mid-ocean exchange regulations for international commercial vessels entering Canadian ports (Transport Canada, 2006). These regulations were implemented to minimize the transport of potential harmful NIS via ballast water into Canada (Sun et al., 2010). Currently, the regulations require all intra-coastal commercial vessels south of Cape Blanco, Oregon, south of Cape Cod, Massachusetts, and transoceanic commercial vessels to perform a mid-ocean exchange outside of the Canadian exclusive economic zone in water depth deeper than 2km (Transport Canada, 2006).  15     Although the mid-ocean exchange regulation may prevent current and further NIS introductions into Canada, port vulnerability to NIS not only stems from the constant input of propagule pressure by ballast water and other commercial shipping vectors, but the fact that this type of ecosystem is already heavily disturbed and manipulated by other anthropogenic activities, such as pollution, construction, and other habitat modification activities (Johnston et al., 2009). Anthropogenic activities have been known to open up habitats for NIS settlement, either through creation of new habitats or destruction of native habitats, which could influence NIS establishment success. Each Canadian coastline (Pacific and Atlantic) have experienced its share of anthropogenic activities (shipping and port development), which has the potential to shape how each coastal region is influenced by NIS. The history of Pacific and Atlantic ports of Canada are different. Not only do they have distinct physical environments, their history of marine commercial activities evolved differently and was influenced by different events. The Atlantic coast of Canada was one of the first regions in Canada to be settled by Europeans. This coast is an example of a port ecosystem that has been consistently impacted by commercial shipping activities for centuries, e.g. an area that might have had and a long history of NIS introductions. Atlantic Canada was officially settled in the early 1700’s by Colonel Edward Cornwallis (Frost, 2008), and with the development of the coastal ferry service in 1751 in Halifax, over 2500 European settlers arrived on the Canadian Atlantic coast (Frost, 2008). In 1818 Halifax became a “free port” and international trade between foreign countries outside of the British Empire was thus officially commissioned and the Atlantic coast became the dominant trading hub in Canada. Imported goods received for most provinces were largely received by ports in Nova Scotia and New Brunswick (Frost, 2008). The decline in relative importance of the Atlantic coast as a major international trade route began in 1914, when the Panama Canal was built (Steven, 1936). Most of Canada’s valuable natural exports, lumber and grain, were rerouted 16     to the Port of Vancouver for international export because transporting goods via rail from the Atlantic coast was much more expensive than marine transport through the Panama Canal (Steven, 1936). The Canadian Atlantic coast fell even further in importance as an international trade in 1966 when augmented ice breaking opened the St. Lawrence waterways to winter trade. In the modern era the Port of Halifax, the largest port in Atlantic Canada, is ranked only as the seventh leading port in Canada, overshadowed by the ports in the Great Lakes region (Port of Montreal, etc.) and on the Pacific coast (Port Metro Vancouver) (Transport Canada 2007). International marine activities on the Canadian Pacific coast began differently than the Canadian Atlantic coast. Although the Canadian Pacific coast has had a shorter history of commercial shipping activities than the Atlantic coast, over the last 100 years it has experienced intense shipping activities. When the Pacific coast was first colonized, international marine traffic was at a minimum because trade goods were transported from the east via inland transport (Steven, 1936). The main marine traffic was driven by the lumber industry and remained local. Timber was transported from remote inlets to ports for inland transport to the rest of Canada (Steven, 1936). It was not until 1914, with the opening of the Panama Canal, that marine traffic began to hold importance on the Canadian Pacific coast by bringing Europe closer (Steven, 1936). In addition, with the rising cost of rail transport, marine trade routes became increasingly important as the colonization of the west continued. The impact of the extra marine traffic is reflected in opening of the Port of Prince Rupert in 1916, which is currently one of the largest ports in Canada (Transport Canada, 2007). By 1920, international trade on the Pacific coast of Canada had outcompeted the Atlantic coast. For example, by 1918, the Pacific coast extended its lumber export to the United Kingdom, Japan, China, Australia, the United States, and Mexico (Steven, 1936). In 1924, the tariff for westbound freight was lifted. The reduction in westward freight rates opened opportunities for grain to be exported from the Canadian Pacific coast, 17     resulting in increased trade along the Pacific coast (Steven, 1936). By 1930, the Port of Vancouver became the largest port in Canada for exports, outcompeted the Port of Montreal and the Port of Halifax (Steven, 1936; Transport Canada, 2007). In the modern era, Port of Vancouver, renamed as Port Metro Vancouver and the Port of Prince Rupert are two of the largest ports in the Pacific Northwest of North America (Transport Canada, 2007).  1.6 Thesis Objectives The purpose of this study is to examine intertidal NIS establishment patterns in Canadian port communities. Of the many communities in ports, intertidal communities have been studied by many notable invasion ecologists in the United States (Cohen et al., 1995; Cohen & Carlton, 1995; Grosholz & Ruiz, 1996; Cohen, 1998; Ruiz et al., 2000a; Cohen & Chapman, 2005), but invasion studies on intertidal communities in Canadian ports are rare. This study will be the first to examine intertidal NIS in both the Pacific and the Atlantic coast of Canada to generate an overall survey on the general distribution of intertidal NIS in Canadian ports. An overall survey can be used to determine and compare the similarities and the differences in NIS distributions between two coasts. Traditionally, invasion studies usually examine each coast separately, and many of the comparisons and invasion results made between the two coasts have been anecdotal. This study will empirically compare the intertidal port communities on both coasts. The similarities and differences of NIS distribution between the two coasts are especially interesting given there are significant differences not only in the intertidal characteristics between the two Canadian coasts but also differences in commercial trade history. If commercial shipping activities do have an influence on NIS establishment success, as proposed by invasion hypotheses in the past (Carlton, 1987; Ruiz et al., 2000a; Coutts et al., 2003; Holeck et al., 2004; Bailey et al., 2005; Duggan et al., 2005; Ricciardi, 2006; Kelly et al., 2009), the different histories of each coast should be reflected in established NIS.   18     In addition to comparing distributions of NIS and native species in intertidal communities of Canadian ports, it is interesting to examine the propagule supply hypothesis in Canadian ports. The hypothesis suggests that propagule pressure from commercial shipping activities is considered the major influence on NIS establishment. Current studies that support this hypothesis report data collected at the initial dispersal stage, such as the amount of living organisms found inside ballast tanks or fouled on hulls (vector strength). Large magnitude of the vector strength or propagule pressure are observed in ballast water that have lead to this hypothesis that introduced NIS can overcome all invasion filters to establish and integration into new habitats. But a direct relationship between Stage 2, introduction and primary dispersal of NIS through propagule pressure, and Stage 4, integration of NIS into new regions are still needed to fully support this hypothesis. Past studies have attempted to examine this relationship in marine communities but results have not clearly demonstrated this relationship (Levings et al., 2002; Johnston et al., 2009). This study will attempt to investigate this hypothesis by examining any relationship between dispersal of NIS through propagule pressure from commercial shipping (Stage 2) and the distribution patterns of established NIS in intertidal communities of Canadian ports (Stage 4). In general, this study will focus on assessing non-indigenous intertidal invertebrates and algae across 16 international ports in the Pacific and Atlantic coasts of Canada. The assessment will address the following overall objectives: 1) To characterize and assess NIS established in intertidal communities of Canadian ports, which includes species presence, richness, diversity, and relative abundance. This will be the first study that provides a comprehensive list of marine intertidal NIS on both the Pacific and Atlantic coasts of Canada.  19     2) To compare the overall community structure of intertidal communities between Pacific and Atlantic Canadian ports. This includes comparing species richness, species diversity, and the relative degree of invasion between communities. 3) To determine if propagule pressure from commercial shipping activities (ballast water discharge, vessels arrival frequency, etc.) influences NIS establishment success. This will relate propagule pressure from commercial shipping to NIS richness or abundance. 4) To determine other abiotic variables, including environmental (sea surface temperature and salinity) and local anthropogenic (human population, aquaculture dispersal, etc.), that could influence, as either filters to prevent or factors that promote NIS establishment in intertidal communities of Canadian ports, and examine if the effect of these variables are consistent between the Pacific and Atlantic coasts of Canada. Overall, the research from this thesis will increase our understanding of intertidal NIS in Canada. It can provide information about NIS distributions in intertidal port communities that could be used to compare to other port and marine regions around the world. Ultimately, this thesis aims to provide a long term contribution to the literature on marine biological invasions in order to improve scientific understanding that can be used to find efficient methods to prioritize, manage, and conserve environments that could be impacted by aquatic invasive species.  20     2  EXAMINING INTERTIDAL NIS PATTERNS AMONG PACIFIC AND ATLANTIC CANADIAN PORT COMMUNITIES  2.1 Introduction Invasion by non-indigenous species (NIS) in freshwater and marine communities is considered one of the most important biological concerns worldwide (Moyle 1999). The direct negative impacts of marine NIS on fisheries and aquaculture operations are well documented (Ramsay et al., 2008; Therriault and Herborg, 2008; Epelbaum et al., 2009; Herborg et al., 2009) and there is growing evidence that invasive species have the ability to alter ecosystems by negatively affecting native species communities, and reducing the ecological integrity of native systems (Bax et al., 2003; Colautti et al., 2006; Ricciardi and Kipp, 2008; Williams & Grosholz, 2008; Shao, 2009). Several literature reviews have documented the role of commercial shipping as a vector that increases the probability of marine invasions. As a consequence, the presence and impacts of NIS are assumed to be magnified in ports and harbours (Ruiz et al., 1997; Cohen, 1998; Bax et al., 2003; Minton et al., 2005; Colautti et al., 2006) where introduction rates are assumed to be higher. Commercial shipping is a primary vector responsible for transporting NIS to a new region (Ruiz et al., 1997; Cohen, 1998l; Larson et al., 2003; Colautti et al., 2006). In their native habitat organisms can be taken up with ballast water (Minton et al., 2005) or attach to the hull of commercial vessels (Bax et al., 2003). The organisms subsequently are deposited, often at high concentrations, in non-native, receiving habitats (Ruiz et al., 1997; Cohen, 1998; Larson et al., 2003) and should favourable conditions be encountered, these NIS can become established. Propagule pressure is a measure of the number of organisms released into a non-native habitat (Carlton, 1996; Johnston et al., 2009) and is critical component of invasion dynamics. Current theory suggests that increased propagule pressure enhances NIS establishments (Ruiz et al., 21     1997; Cohen, 1998; Williamson, 1999; Ruiz et al., 2000 b; Larson et al., 2003; Minton et al., 2005; Colautti et al., 2006; Johnston et al., 2009). Therefore in ports, where propagule pressure by commercial vessels is expected to be high one would expect to find the greater richness and abundance of NIS compared to adjacent environments with limited propagule pressure. Finding effective methods in managing marine invasive species communities in ports have been difficult (Williamson, 1999). Particularly in intertidal habitats, as they are considered one of the most vulnerable habitats to invasion due to the heavy stresses occurring in these habitats. Intertidal communities are naturally heavily stressed by daily tidal cycles and species living in these habitats have to tolerate extreme changes in temperature, salinity and air exposure. In addition, other anthropogenic factors such as pollution, physical disturbance and creation of additional habitats may accompany the high rates of natural disturbance. High levels of disturbance often have been invoked to explain enhanced numbers of NIS (Elton, 1958). So in order to manage the invasion on intertidal NIS efficiently, fundamental steps are needed to understand the patterns of NIS in these highly disturbed communities before determining which disturbances have the greatest influence towards NIS introduction and establishment. Overall, our understanding of marine intertidal NIS in Canada is poor. A number of previous studies had assessed NIS composition in ports (Cohen, 1998; Cohen & Carlton, 2005; Cohen et al., 2005; Wyatt et al., 2005). However, few have looked specifically at the intertidal habitats and even fewer studies have observed invasions in intertidal communities in Canadian ports. It is documented that the Pacific and Atlantic intertidal communities are very different from each other mainly due to both physical conditions and the history in their marine commercial trades (Larson et al., 2003). Many first-hand observations have suggested that the intertidal communities in Atlantic Canada have low species diversity, while Pacific intertidal communities are species rich. This was resonated with American studies that have shown the 22     Pacific intertidal communities had higher total species diversity and NIS diversity (Ruiz et al., 1997; Roy et al., 1998; Ruiz et al., 2000a). Under traditional invasion ecology theory, when establishment of NIS depends on the biological resistance of native species, it can be hypothesized that communities with lower native diversity should be more susceptible to invasion (Elton, 1958; Tilman, 1997). According to this theory, the Atlantic intertidal communities should be more invaded than their Pacific counterparts. However, extensive comparative studies testing this hypothesis are lacking. A detailed inter-comparison of port intertidal communities of the Pacific and Atlantic coast can bridge the gap between documented encounters and scientific knowledge on the community structure of native and non-indigenous species of intertidal communities in Canadian ports. Comparative studies can examine and reveal patterns of NIS establishment, and identify whether the patterns follow similar trends in both intertidal coastal regions despite their differences in locations, physical conditions, and history of anthropogenic activities. A detailed inter-comparative field survey of intertidal communities in Pacific and Atlantic Canadian ports was conducted. The main objectives of this chapter were to: (a) create an inventory of intertidal megafauna in selected harbours on the Pacific and Atlantic coasts of Canada; (b) obtain detailed assessment of intertidal communities based on native and nonindigenous megafaunal species; and (c) examine and compare NIS patterns both within and among coasts. To achieve objectives of this chapter, measuring invasion in each community is crucial. Quantitative methods for measuring invasion could simplify interpretations of the assessments, examinations and comparisons across the studied intertidal communities in ports. Quantifying invasion is difficult at a community level. Past studies have hypothesized that diversity indices can be indicators of invasion (Tilman, 1997; Schooler et al., 2006). McGeoch and colleges have 23     used species richness as a proxy to compare the effects of invasive species across European countries (McGeoch et al., 2010). However, using diversity indices to measure invasion in marine communities appeared to be problematic for a number of reasons. Marine invasion studies in the past have failed to use diversity indices as a method in comparing invasions across study sites (Jewett, 2005; Wyatt et al., 2005). The inherent bias in each diversity index has prevented their consistent application as indicators of invasion status (Drake et al., 1999; Jewett, 2005; Wyatt et al., 2005). Other measurements of invasion also were difficult or time consuming to generate. For example, measuring the sum of impacts by all NIS using transplant experiments and comparing changes in biological, environmental, and economical effects between controlled and manipulated sites appeared to be logistically challenging (Parker et al., 1999). As a way forward, complex models with general hypothesized factors that could impact the community of interest were created (Parker et al., 1999; Magee et al., 2010). Examples of complex invasion models include the risk assessment of Ciona intestinalis (Therriault & Herborg, 2008) or the invasiveness-impact score (Magee et al., 2010). Both examined multiple effects of a specific species on a community. Data requirements for these models are high and likely only readily available for a few, selected, high profile invaders. High complexity and data requirements render measures of this type inefficient for measuring invasion for time sensitive studies, such as rapid assessment. Measuring and calculating invasion by using the sum of NIS impacts also is not ideal in community studies. Communities are rarely affected by a single invader (Cohen & Chapman, 2005; Cohen et al., 2005; Coles et al., 2006; Magee et al., 2010). Multiple NIS can be introduced simultaneously, such as via ballast water release events into the marine system (Minton et al., 2005), or sequentially, when multiple vectors deliver species to a common ecosystem (Cohen et al., 2005). Further, facilitation between invaders could result in greater impacts on the native 24     community than either single-species effects independently (Simberloff and Von Holle, 1999; Magee et al., 2010). Thus, simply summing individual NIS impacts thus may not adequately represent the community-level impacts imposed by multiple invaders (Parker et al., 1999). As a result, it is important to assess and measure invasion in a community as an integrated process. In this chapter, a novel index is introduced to calculate and measure invasion called the Invasion index. The Invasion index is the proportion of overall NIS in each community and it can be interpreted as the probability of randomly choosing two individuals from a given area and having both of those two individuals be NIS. More simply, it is the probability of encountering a non-indigenous individual in a community. The proportion of NIS in a community is a good indicator for measuring invasion because it considers the contribution of NIS within native communities that acts as a proxy of potential impacts or effects of an invasion (e.g., greater invaders represent greater impacts). Specific effects could be the result of NIS competitive dominance over native species for limiting resources such as food or space (Parker et al., 1999). Many terrestrial invasion studies have shown that once NIS over-dominate in a community, changes in productivity, richness and health of the community follow (Alphine & Cloern; 1992; Cleland et al., 2004; Sanchez et al., 2005; Schooler et al., 2006; Gremmen & Smith, 2008). This chapter will use the Invasion index and as well as other common measurements of the community diversity to assess and analyze the variation of community differences across the intertidal communities in ports of the Canadian Pacific and Atlantic coasts.  2.2 Methods and Materials Study sites Intertidal surveys were conducted in 16 international ports on the Pacific (8) and Atlantic (8) coasts of Canada between the summer of 2007 and 2008 (Figure 2-1, Table 2-1). The Pacific and Atlantic coasts were represented by the coastal area of British Columbia and the eastern 25     coast of Nova Scotia, respectively. Within each port, six replicate sampling locations (sites) were surveyed. Site coordinates were recorded using a hand held GPS unit. In total, 96 sites (48 on each coast) were surveyed for this study. At each study site, two types of biological surveys were conducted to characterize intertidal macro-species assemblages; (1) a timed walk survey with the main purpose to characterize the species richness, and (2) a quadrat survey to assess relative abundance and biomass of intertidal organisms. Field surveys Timed walk surveys represented a rapid, qualitative assessment of the community for the presence of species (Cohen et al., 2005). The assessment for each site was done throughout the intertidal range, which included the low, mid and high intertidal zones. Standardized search effort (30 minutes) timed walks were conducted at each site, with the effort evenly divided among the three zones; 10 minutes in each zone. Most organisms were collected in bags, preserved with formalin, and transported back to the laboratory at the University of British Columbia (UBC) for species identification. Larger organisms that could be identified in the field were not collected but photos were taken for documentation. In addition to identifying species presence, the timed walk survey also recorded the habitat of each species. This included intertidal zones (high, mid, low) and the sediment types (rocky, sandy, boulder, etc.) each species was found on.  26     Figure 2-1. Study sites from the Canadian intertidal survey. White dots represent the 16 international ports surveyed on the Pacific a) and Atlantic b) coasts of Canada  27     Table 2-1. List of ports sampled on the Canadian Pacific and Atlantic coasts  Pacific coast sites  Coordinates  Atlantic coast  Coordinates  Campbell River  50.065N 125.268W  Halifax  44.686N 63.614W  Cowichan Bay  48.701N 123.548W  Little Narrows  46.098N 60.743W  Esquimalt  48.451N 123.441W  Liverpool  44.043N 64.707W  Kitimat  53.982N 128.699W  Point Tupper  45.585N 61.348W  Nanaimo  49.197N 123.945W  Sheet Harbour  44.893N 62.476W  Port Alberni  49.234N 124.814W  Shelburne  43.732N 65.352W  Prince Rupert  54.337N 130.309W  Sydney  46.127N 60.212W  Vancouver  49.316N 123.132W  Yarmouth  43.807N 66.131W  28     The quadrat survey provided a quantitative assessment of species richness and abundance (Cohen et al., 2005). At each site, in three intertidal zones (low, mid, and high), four randomly placed 50cm x 50cm quadrats were excavated to a depth of 20cm providing a total of 12 quadrats for each site. Sediment was placed in a sieve with mesh size of 1cm x 1cm to isolate organisms from the sediments. All organisms isolated in the sieve were collected and persevered in 4% formalin in bags with site specific labels. Bags were transported back to the University of British Columbia for identification. At the lab, species presence and abundances were recorded for each quadrat. Regardless of survey type, species were identified to the lowest taxonomic level possible and classified as native, non-indigenous and cryptogenic, according to multiple taxonomic keys for the Pacific coast marine invertebrate species (Rudy et al., 1983; Kozloff & Price, 1996; Coan et al., 2000; Gabrielson et al., 2000; O’Clair & Lindstrom, 2000; Levings et al., 2002; Lamb & Hanby, 2005; Light & Carlton, 2007; ITIS) and in the Atlantic coast (Gosner, 1978; Pollock, 1998; ITIS). Measuring communities Data collected during biological surveys were manipulated to create two datasets: species composition dataset and abundance composition dataset. The species composition dataset was built by pooling all species present from the timed walk and quadrat surveys from each port, which means that only species presence/absence was recorded in this dataset. The abundance composition dataset was compiled using the data from quadrat surveys only. Unlike the species composition dataset, this dataset contained a species list as well as their relative abundance at each site. Community diversity (both native diversity and NIS diversity) for each port was calculated using three different diversity indices: species richness (Peet, 1974), Shannon-Wiener diversity index (Wiener, 1948; Shannon & Weaver, 1949) and Simpson’s diversity index 29     (Simpson, 1949). Measuring native and NIS diversity enables examinations of the changes of native diversity with variations of NIS diversity. Species richness calculates the number of species present at each site, while Shannon-Wiener diversity index and Simpson’s diversity index combine the richness and the relative abundance of each species in a community (eq. 2-1, 2-2). Shannon-Wiener diversity index emphasizes the equality of species abundance within the community (eq. 2-1): H’ = -∑ pi ln pi  (eq. 2-1)  where pi is the number of individuals found in each site for species i. Similar to the Shannon-Wiener diversity index, the Simpson’s diversity index also incorporates species richness and relative abundance of each species in the community but this index highlights the dominance or inequality in the abundance of species in the community (eq. 2-2). Therefore, the Simpson’s diversity index interprets diversity as the probability of having no dominance of a specific species in the community: D = 1 – [ ∑ pi (pi-1)] / [N(N-1) ]  (eq. 2-2)  where pi is the number of individuals found in each site for species i and N is the total number of individuals found in each site. Diversity indices were calculated for each site. In each port, the diversity indices across the six sites were averaged to determine the average species richness, Shannon-Wiener and Simpson’s diversity index for each port. Community invasion for each port was calculated with the Invasion index (eq. 2-3), which can be abbreviated to Phi). The Invasion index is simply the proportion of nonindigenous individuals in each community:  = [i x (i-1)] / [N x (N-1)]  (eq. 2-3)  where i is the abundance of total NIS found in each site and N is the abundance of total species found in each site (Appendix A). Abundance can be either the number of non-indigenous 30     individuals, percent cover of NIS in a given area, or the biomass of NIS in a given area (Parker et al., 1999).  ranges between 0 and 1, where 1 would be a community where all individuals are non-indigenous and 0 when none of the individuals are non-indigenous. A reference point of 0.25 is established for the Invasion index, where is greater than 0.25, the invasion effects would become progressively greater on the community (Appendix A). This study used the number of individuals as abundances for the equation parameters: i and N. The number of individuals at each site were taken and pooled together from the species composition dataset. The calculated values were averaged across the six sites in each port to determine and compare invasion across the ports. These averaged Invasion indices of ports were also used in nested analysis to compare the invasion between the two coasts. Although the Invasion index looks similar to the Simpson’s diversity index (eq. 2-2), it is important to note that while Simpson’s diversity index measures the sum of abundance dominance for each species (Simpson, 1949); the Invasion index sums all non-indigenous individuals and measures the dominance of all nonindigenous individuals as a group regardless of which NIS the individuals represent (metaspecies). Data analysis Comparisons among the ports within each coast and between the two coasts with respect to species richness, Shannon-Wiener diversity index, Simpson’s diversity index and the Invasion index were analyzed using analysis of variance (ANOVA). The Invasion index from the Pacific coast and the Shannon-Wiener and Simpson’s diversity indices from both coasts were log transformed to normalize distributions to meet assumptions for ANOVA. Nested ANOVA was used to statistically compare the differences between the coasts with ports nested within their associated coast. For among port comparisons within each coast, ANOVA was used to statistically compare the differences and Tukey’s honestly significant difference (HSD) test was 31     performed to reveal the specific patterns among ports on each coast. ANOVA and Tukey’s HSD tests were performed with statistical program JMP 7.0 from Statistical Analysis Software (SAS). In addition to univariate analysis, intertidal communities in ports within each coast were examined using multi-variate statistical analyzes. Different types of multi-variate statistical methods were used to analyse the community structure among the ports on the Pacific and the Atlantic coast. First, to determine the different types of community structure on each coast, hierarchical cluster analysis was employed to create cluster groups. Each cluster group would be based on sampling sites with similar species assemblages. Next, similarity percentage routine (SIMPER) was used to examine the type of species (native or non-indigenous) that contributed to the differences across the cluster groups. SIMPER examined the presence and relative abundance of all species in two clusters to determined, in percentage, the species that contributed to difference of the clusters. SIMPER ranked the species with the greatest contribution to the differences to the lowest. In this study, the contributed species were identified and separated by either native or non-indigenous to determined sums of native and non-indigenous species contributed to the differences of the clusters. The percentages of contributions by native and non-indigenous species between clusters were averaged to represent the average contribution to community structure for each coast. The average NIS contribution to the differences in clusters/species compositions of the Pacific and the Atlantic coast were analyzed through analysis of variance (ANOVA) or Welch ANOVA (non-parametric) to determine any significant differences in NIS contributions to community structure between the two coasts. Cluster analysis and SIMPER analysis were performed using the Plymouth Routines in Multivariate Ecological Research (PRIMER 6) program (Clarke & Gorley, 2006).  32     2.3 Results Overall, 304 algae and invertebrate species were identified on the Pacific coast, 20 of which were NIS (Appendix B). According to published sources (Cohen & Carlton, 1995; Levings et al., 2004), out of 20 NIS, eight NIS had been identified as possible introductions through ballast water discharge (Table 2-2). On the Atlantic coast, in total 112 species were identified with only six NIS recorded (Appendix B). Average native and non-indigenous species richness in the Pacific coast ports was 26.40 species ± 22.6SD and 2.49 species ±3.0SD per port, respectively (Figure 2-2a). Average native species richness on the Atlantic coast was 4.64 species ±8.1SD and NIS averaged 1.31 species ±1.9SD per port (Figure 2-2b). The Pacific coast had a significantly higher mean species richness than the Atlantic coast in both native (Welch ANOVA, F15, 70 = 19.22, p= 0.001) and NIS (Welch ANOVA, F15, 70= 3.34, p= 0.001) (Table 23).  Table 2-2. List of NIS that are potentially introduced by ballast water discharge Species  Common class  References  Alcyonidium gelatinosum  Bryozoan  Cohen & Carlton, 1995  Amphithoe valida  Amphipod  Cohen & Carlton, 1995  Caprella mutica  Amphipod  Cohen & Carlton, 1995  Carcinus maenas  Arthropod  Cohen & Carlton, 1995  Nuttallia obscurata  Bivalve  Levings et al., 2002  Pseudopolydora kempi  Polychaete  Cohen & Carlton, 1995  Ptilohyale littoralis  Amphipod  Cohen & Carlton, 1995  33     Shannon-Wiener diversity for native species ranged from 1.19 at Port Alberni to 2.56 at Campbell River on the Pacific coast with the mean of 2.00 ±1.5SD. Within the Pacific coast, Shannon-Wiener native diversity indices among the ports were found to be significantly different from each other (ANOVA, F7, 39=6.54, p= 0.001). Tukey’s HSD test revealed five different groups of ports based on the Shannon-Wiener native diversity index (Figure 2-2c). For NIS, Shannon-Wiener diversity ranged from 0 at Prince Rupert to 1.06 at Vancouver with the mean of 0.51 ±0.9SD. Shannon-Wiener diversity indices for NIS among the ports also were significantly different (ANOVA, F7, 39=8.54, p= 0.001). Tukey’s HSD test revealed six different groups of ports based on the Shannon-Wiener NIS diversity index (Figure 2-2c). On the Atlantic coast, Shannon-Wiener native diversity ranged from 0.37 at Halifax to 0.90 at Little Narrows. Average Shannon-Wiener native diversity on the Atlantic coast was 0.83 ±1.2SD (Figure 2-2d). ShannonWiener diversity for NIS ranged from 0 at Little Narrows to 0.22 at Yarmouth. The mean Shannon-Wiener diversity for NIS was 0.12 ±0.5SD (Figure 2-2d). No significant differences in Shannon-Wiener of both native and NIS diversity were found among ports. Shannon-Wiener diversity between the two coasts also revealed significantly higher diversity in native and nonindigenous species on the Pacific coast compared to the Atlantic coast (nested Welch ANOVA: native: F15, 70 = 43.5, p = 0.001; NIS: F15, 70 = 19.98, p = 0.001) (Table 2-3). Simpson’s native diversity ranged from 0.55 at Port Alberni to 0.84 at Esquimalt on the Pacific coast with the mean of 0.73 ±0.5SD. Using Welch ANOVA test, Simpson’s native diversity indices among the ports were not found to be significantly different from each other. For NIS on the Pacific coast, Simpson’s diversity ranged from 0 at Prince Rupert to 0.73 at Vancouver with the mean index of 0.37 ±0.7SD. Simpson’s NIS diversity indices among the ports were found to be significantly different from each other (ANOVA, F7, 39=7.64, p= 0.001). Tukey’s HSD test revealed three different groups of ports based on the Simpson’s NIS diversity 34     index (Figure 2-2e). For the Atlantic coast, mean Simpson’s diversity for native species was 0.40 ±0.8SD. The range among the ports was 0.21 at Liverpool to 0.70 at Little Narrows (Figure 22f). For only NIS, mean Simpson’s diversity was 0.12 ±0.6SD, which ranged from 0.03 at Sheet Harbour to 0.30 at Little Narrows (Figure 2-2f). No significant differences in Simpson’s of both native and NIS diversity were found among the ports. Ports on the Pacific coast had significantly higher native and non-indigenous Simpson’s diversity than the Atlantic coast (Nested Welch ANOVA, native: F15, 70 = 32.71, p = 0.001; NIS: F15, 70 = 18.65, p = 0.001) (Table 2-3).  35     Figure 2-2. Biological diversity index of the Pacific and Atlantic coast of Canada separated by ports. Species richness index of the Pacific a) and Atlantic b), Shannon-Wiener (S-W) diversity index of the Pacific c) and Atlantic d) coast (n = 6 sites per port) and Simpson’s diversity index of the Pacific e) and Atlantic f) coast (n = 6 sites per port). White and black bars represent the native and non-indigenous species (NIS) diversity for each port, respectively. Dotted line represents the average coastal native species diversity, while the black solid line represents the average coastal NIS diversity for each coast. Letters inside each bar represent Tukey’s HSD test results. Ports with different letters represent significant differences in diversity index  36     Invasion index calculated for ports on the Pacific ranged from 0 at Prince Rupert to 0.51 at Nanaimo. Invasion index among the Pacific ports was found to be significantly different from each other (Welch ANOVA, F7, 14=4.099, p=0.0111). Tukey’s HSD test revealed two different groups of ports based on the Invasion index (Figure 2-3a). For Atlantic ports, the Invasion index ranged from 0 at Little Narrows to 0.75 at Sydney. No significant differences in Invasion index were found among the Atlantic ports. Mean Invasion index for the Pacific coast was 0.07±0.3SD, while the Atlantic coast’s mean Invasion index was 0.46 ±0.4SD (Figure 2-3b). The Atlantic coast had a significantly higher Invasion index than the Pacific coast (Nested Welch ANOVA: F15, 70 = 41.39, p = 0.0001) (Table 2-3).  37     Figure 2-3. Invasion Index of the Pacific a) and Atlantic b) coast, separated by ports (n=6 sites per port). The Invasion index for each port is shown above its respected bars. Letters inside each bar represent Tukey’s HSD test results with the Invasion index. Ports with the different letters represent significant differences in Invasion index. Solid lines represent the mean of the Invasion Index (n=8 ports per coast)  38     Table 2-3. Comparing nested Welch ANOVA of average indices between Pacific and Atlantic coast of Canada. Significant differences between coasts (F test, p-value < 0.05) are indicated by * Pacific  Atlantic  F-ratio  p-value  Native species richness  26.40  4.64  19.22  0.001*  NIS richness  2.49  1.31  3.34  0.001*  Total Shannon-Wiener diversity index  2.00  0.83  43.5  0.001*  NIS Shannon-Wiener diversity index  0.51  0.12  11.98  0.001*  Total Simpson`s diversity index  0.73  0.34  32.71  0.001*  NIS Simpson`s diversity index  0.40  0.12  18.65  0.001*  Invasion index  0.07  0.46  41.39  0.0001*  39     Hierarchical cluster analysis determined different types of species composition on the Pacific coast at dissimilarity levels of 60% or lower. Four significantly different species assemblages emerged (p = 0.001) (Figure 2-4). First species assemblage, including sites at Campbell River and Cowichan Bay, grouped apart from the other three assemblages at a dissimilarity of 76.5%. At a dissimilarity of 68.6%, the second assemblage, including sites at Kitimat and Port Alberni, clustered apart from the third and fourth assemblages. Finally, the third assemblage, sites from Prince Rupert separated from the fourth assemblage, including Vancouver, Nanaimo and Esquimalt at dissimilarity level of 61.2%. SIMPER analysis demonstrated that there was a high degree of dissimilarity (on average 75.8%) between the clusters of intertidal assemblages on the Pacific coast. The dissimilarity across clusters were largely attributed to native species, on average 91.0±4.1%, while NIS contributed relatively little to the dissimilarity, on average only 9.0±3.4%. On the Atlantic coast, multivariate cluster analysis at a dissimilarity level of 60% or higher revealed seven significant species assemblages on the Atlantic coast (Figure 2-5). Assemblages with mostly single harbours, Little Narrows, Sheet Harbour and Sydney became significant assemblages at dissimilarity levels of 83.8% (p=0.001), 64.7% (p=0.007) and 65% (p=0.002), respectively. The remaining three assemblages: a combination of sites from Liverpool, Point Tupper and Yarmouth separated at a dissimilarity level of 79.5% (p= 0.001), a combination of sites from Shelburne and Yarmouth separated at 64.7% (p= 0.007) dissimilarity level and a combination of Halifax and Point Tupper sites separated at 65% (p= 0.002) dissimilarity level. SIMPER found a high degree of dissimilarity (on average 81.9%) between identified assemblages. Non-indigenous and native species contributed almost equally to differences between assemblages, on average 44.5±13.7% for NIS and 55.5±11.8% for native species. The average contributions by NIS to the differences in community structure of the two 40     coasts were compared. ANOVA analysis revealed the average contribution by NIS to community differences was significantly higher on the Atlantic coast than the Pacific coast (F7,32=133.98, p=0.001).  41     Figure 2-4. Cluster analysis from Pacific coast species richness dataset. Intertidal sites are grouped together based on the similarities in species richness. Black solid lines on linkage tree represent significant differences in grouping. Faded lines represent no significant differences in grouping    42     Figure 2-5. Cluster analysis from Atlantic coast species richness dataset. Intertidal sites are grouped together based on the similarities in species richness. Black solid lines on linkage tree represent significant differences in grouping. Faded lines represent no significant differences in grouping     43     2.4 Discussion Invasion measurements Overall, NIS had different occurrence patterns and diversities in intertidal habitats between the Pacific and the Atlantic coast. This study collected a total of 20 NIS on the Pacific coast compared to only six NIS on the Atlantic coast. Unlike other diversity indices (ShannonWiener, Simpson’s diversity), the proposed Invasion index allows an objective interpretation of invasion levels. It appears that the Invasion index is an accurate and standardized method to characterize the relative level of invasion by multiple invaders in native communities. The index that could be based on abundance, percent cover or biomass of NIS, is defined as the probability that two individuals, encounter independently, will be non-indigenous. According to the Invasion index results, the Atlantic coast is significantly more invaded than the Pacific coast. The Invasion index demonstrates that native species and/or limited resources have higher probability of encountering NIS in the Atlantic coast than the Pacific coast. The Atlantic coast had an average Invasion index of 0.46, while the average Invasion index on the Pacific coast was only 0.07. The average Invasion index in the Atlantic ports surpassed the 0.25 reference point, suggesting that invasions are getting progressively worst in communities as each non-indigenous individual are being added to the community. According to the equation, as the Invasion index exceeds 0.25, the slopes of the Invasion index become steeper with each additional individual (Appendix A). Therefore, once pass the reference point, as each non-indigenous species is added to the community, the change in the Invasion index value becomes greater. In the Pacific ports, the average Invasion index is well under the reference point suggesting that the effects of invasion on the communities are not as apparent, as the slopes of the Invasion index do not change as drastically when under the reference point. Based on the Invasion index, the simple interpretation of the invasion status of the two coasts is, on average, the Atlantic coast has 46% 44     probability that native species or limiting resources will encounter two NIS individuals in the intertidal community. The Pacific coast will have an average probability of 7% that two NIS individuals will be encountered one after another. Invasion studies in the past have demonstrated that NIS abundance does have an effect on native productivity, either through predation, competition or facilitation (Alpine & Cloern, 1992; Cleland et al., 2004; Huston, 2004; Sanchez et al., 2005). Native productivity could be a proxy to signify the NIS effect on a community. According to the results of the Invasion index and the relationship of NIS abundance and native net productivity, this chapter proposed that the intertidal communities in Atlantic ports are more heavily impacted compared to Pacific ports. Similarly to the Invasion index, previous studies have confirmed inter-coastal differences in Canada. For example, studies on the European green crab, Carcinus maenas, repeatedly reported higher impacts of this invader along the Atlantic coast compared to the Pacific coast (McDonald et al., 2003; Jensen et al., 2007; Brawley et al., 2009; See & Feist, 2010). Furthermore, studies in subtidal habitats also have documented similar trends as a smaller number of NIS on the Atlantic coast cause considerably higher impacts on aquaculture and fisheries than the same or similar species on the Pacific coast (Clarke & Therriault, 2007; Locke et al., 2007; Ramsay et al., 2008; Therriault & Herborg, 2008). There are a few different hypotheses proposed to explain potential differences in invasion between the two coasts. Jensen et al. (2002) suggested that the west coast of North America is more resilient to NIS establishment due to biological resistance owing to the substantially larger variety (diversity) of native species. It was hypothesized that the richness of native species may act as a strong resistance filter limiting the settlement and establishment of new biological arrivals (Elton, 1958; Jensen et al., 2002). Another common hypothesis concerns differences in the length of exposure to anthropogenic activities between the two coasts. The Atlantic coast had 45     approximately 200 years of consistent international marine traffic before the Pacific coast become internationally commercial, dating all the way back to 1751 (Stevens, 1936; Frost, 2008). It is thus reasonable to hypothesize that the Atlantic coast should be more affected by NIS because of the combination of longer history of the marine international trade resulting in greater propagule pressure (Brawley et al., 2009) and lower native diversity resulting in possibly reduced biotic resistance (Elton et al., 1958; Tilman, 1997; Jensen et al., 2002) is responsible for observed patterns. On the coastal scale, the Invasion index revealed significant differences in invasion among ports on the Pacific and Atlantic coast of Canada. Notably, Nanaimo was significantly more invaded, as suggested by the Invasion index, than the other Pacific ports. On the Atlantic coast, Sydney and Point Tupper had the highest Invasion index. In these highly invaded ports of both coasts, the communities were dominated by NIS accounting for > 75% of all collected individuals. Although this chapter suggests that differences in the Invasion indices between the Pacific and Atlantic could be attributed to the duration of international marine trade, the high Invasion index found in Nanaimo suggests that other factors also are responsible. The former is more applicable to the Atlantic coast, where Sydney and Point Tupper are busy international ports (Bax et al., 2003; Larson et al., 2003). However, the high Invasion index found in Nanaimo port could be attributed to a combination of vectors, including aquaculture, lumber transport, agriculture transport and other commercial shipping activities since 1850 (Niosi & Patterson, 2004). Indeed, the main aquaculture species in the Nanaimo area are all introduced species: Pacific oyster (Crassostrea gigas), Manila clam (Venerupis philippinarum) and varnish clam (Nuttallia obscurata) (Coan et al., 2000; Gillespie & Bourne, 2005). Aquaculture sites, being highly disturbed areas near high traffic international ports, could have been the origin of introductions at Nanaimo (Bax et al., 2003; Larson et al., 2003). 46     The lowest Invasion indices were calculated for Prince Rupert harbour on the Pacific coast and for Little Narrows on the Atlantic coast. It is noteworthy that Prince Rupert, although having the lowest Invasion index, is the second largest port in British Columbia (Stevens, 1936; Transport Canada, 2008). This might suggest the effect of higher latitude in lower invasion risk as evidenced by the low Invasion index observed in Prince Rupert. Hines and Ruiz (2000) examined biological invasions in high latitude regions of Alaska, USA and they established a negative relationship between the number of NIS and latitude. A few explanations were proposed for such a trend. First, NIS appeared to be rare in high latitudes. This was tentatively explained by the stronger resistance of the high latitude habitats to the NIS introduction and establishment. Second, NIS appear to be rare at high latitudes because the recent surge of commercial shipping have not yet impacted these communities to the same extent as those further south. There is a potential delayed response between propagule pressure of commercial shipping and NIS establishment. Finally, it is possible that NIS are common in high latitudes but the scientific effort is still insufficient to provide an informed picture of the NIS invasion in these regions (Hines & Ruiz, 2000) such that a majority of invasions are overlooked. For example, in 1979, 160 NIS were identified in San Francisco Bay. This number increased to 212 by 1995; currently close to 250 species have been identified (Hines & Ruiz, 2000). On the Atlantic coast, Little Narrows had the lowest Invasion index. It is likely that the low marine invasion could be a result of low salinity. The salinity in Little Narrows is heavily affected by the input of freshwater from lakes and rivers. Preliminary measurements of sea surface salinity in Little Narrows revealed sea surface salinity to be much lower than in other ports of the Atlantic coast surveyed. Previous studies have shown that salinity plays an important port in the survival of marine NIS larvae (Mann & Harding, 2003; Hines et al., 2004). With low larval survival, one would expect the establishment rate of NIS to be lower. Another 47     study had recorded much lower non-indigenous bivalve distributions at low salinity sites compare to high salinity sites (Powers et al., 2005).These results are consistent with the interpretation that the low salinity observed in Little Narrows is an important factor that resulted in a lower Invasion index in this port. This is additionally supported by a port on the Pacific coast. Port Alberni and Kitimat have the lowest measured salinity compared to other Pacific ports studied in this chapter. This was accompanied by the low Invasion index in these two ports. In this chapter, the differences in invasion demonstrated through the Invasion index have suggested several potential variables that influence invasions in intertidal communities. High invasion effects could be the result of anthropogenic activities either through nearby commercial shipping activities or aquaculture activities. Low invasion effects could be the result of regions of upper latitudes or lower sea salinity range affecting the establishment of NIS. Diversity measurements In this chapter, multiple diversity indices were calculated and compared between the two coasts of Canada. The results from all three diversity indices revealed that the Pacific coast is higher in diversity of both total species and NIS than the Atlantic coast. Roy and colleagues have also found that within the latitudinal range of 35 - 60oN, the eastern Pacific has higher diversity than the western Atlantic (Roy at al., 1998). American invasion studies also have shown that marine communities in North America have greater NIS diversity on the Pacific coast than the Atlantic (Ruiz et al., 1997; Ruiz et al., 2000a). According to well established traditional ecological theory, communities with high species diversity should be more difficult to invade than communities with lower species diversity due to biological resistance by native species (Elton, 1958; Tilman, 1997). This theory suggests that native diversity and invasion are negatively correlated, as invasion abundance or diversity increases, native species diversity, including richness and abundance, decreases (Tilman, 1997; Schooler et al., 2006). The 48     continuation of invasion, either through increased richness or abundance of NIS, will lead to a decline in the native species diversity with a net result of an overall decrease in the total diversity (Tilman, 1997). The acceptance of this theory allowed many previous studies to use diversity, in the form of diversity indices, as an indicator to measure invasion levels between different sites (Jewett et al., 2005; Wyatt et al., 2005; Schooler et al., 2006). In contrast, the results from this chapter contradict the traditional theory. In fact, this chapter suggested a positive correlation between native diversity and NIS diversity (Figure 2-6); communities with high native diversity also have high NIS diversity. Furthermore, other studies demonstrated similar positive correlation between native diversity and non-indigenous species abundance (Levine & D’Antonio, 1999; Lonsdale, 1999; Sax, 2002; Sax & Gaines, 2003; Stohlgren et al., 2003; Huston, 2004; Davies et al., 2005). All these studies dealt with terrestrial vascular communities, while this chapter is the first to show positive correlation between native diversity and invasibility with the use of marine communities. This positive correlation contradicted the traditional NIS and diversity relationship, which led ecologists to refer this problem as the “invasion paradox” (Fridley et al., 2007; Altieri et al., 2010). As a result, there was a notion to move away from using diversity indices as indicators of the invasion mostly due to the inconsistent patterns observed between the diversity of native and NIS (Jewett et al., 2005; Drake et al., 1999; Sax, 2002; Huston, 2004). This positive correlation pattern observed in previous studies and in this chapter may thus support an alternative hypothesis of NIS establishment. This alternative hypothesis can be called the “environmental-based invasion”. Unlike the traditional theory, where the probability of NIS establishment is based on the biological resistance due to native diversity (Elton, 1958; Tilman, 1997), environmental based invasion hypothesis postulates that NIS establishment is based on environmental conditions (Huston, 2004). According to the environmental-based invasion hypothesis, the establishment of 49     native and non-indigenous species is driven by their similar response to environmental conditions, leading to similar patterns of abundance and richness between native and nonindigenous species (Levine & D’Antonio, 1999; Levine, 2000; Sax & Gaines, 2003; Huston, 2004).  Figure 2-6. Positive trends of native diversity to NIS diversity of both Pacific and Atlantic coast. Diversity measurement is represented through species richness.  The species richness, Shannon-Wiener and Simpson’s diversity index in this chapter all showed similar patterns to the predictions of environmental-based invasion, thus supporting this alternative hypothesis. The high diversity in both total and non-indigenous species in intertidal Pacific coastal communities suggested that the environmental conditions in these intertidal habitats can support a wide range of species. This capacity may be reflected in the higher 50     aquaculture potential of the Pacific intertidal environment (Jensen et al., 2002; Larson et al., 2003; Carswell et al., 2006). A couple of hypotheses have been proposed to explain the influence of high NIS establishment on the Pacific coast. First, it may be influenced by similar favourable conditions that influenced the success of native species (Huston, 2004). Thus, most new species find conditions amenable to establishment. Second, native species that are ecosystem engineers can flourish under favourable environmental conditions and have the ability to facilitate and promote the establishment of NIS (Altieri et al., 2010). In contrast, the Atlantic coast revealed low total and NIS diversity. According to the environmental-based invasion hypothesis, the Atlantic coast, unlike the Pacific counterpart has poor intertidal environmental conditions thereby limiting species richness (Huston, 2004). Past intertidal algal studies have suggested that the poor environmental condition on the Atlantic coast is due to the wide range of environmental variability, e.g. temperature (van den Hoek, 1982; Rietema & van den Hoek, 1984). Environmental variability with the addition of boreal winter climate in the Atlantic coast (which can produce ice scouring) creates a stressful environment for species to flourish. This also can be reflected through the low intensity of intertidal aquaculture observed on the Atlantic coast (LeBlanc et al., 2005). As for NIS establishment, NIS settlement success will depend on the broad environmental tolerances of specific NIS (Huston, 2004). Hence, the explanation for low NIS diversity in intertidal communities of Canadian Atlantic coast could be a combination of several factors. First, lower NIS richness is introduced on the Atlantic coast than on the Pacific coast. Only 14 NIS were recorded to have possible links to introduction through shipping vectors (Pappal, 2010), while 87 NIS are possible introduction through just on one shipping vector: ballast water discharge (Cohen, 1998). Second, speculated under the environmental-based invasion hypothesis, only  51     selected NIS with broad ranges of environmental tolerances could survive settlement and establish under the poor environmental conditions of the intertidal Atlantic port communities. Community structure Four unique species assemblages on the Pacific coast were determined using the cluster analysis. Cluster 1 included sites from Cowichan Bay and Campbell River, cluster 2 consisted of sites from Kitimat and Port Alberni, cluster 3 was composed of sites in Prince Rupert, and cluster 4 was a combination of sites from Vancouver, Esquimalt and Nanaimo. Although, no environmental factors were analyzed in this chapter to determine the cause of dissimilarity, the different types of species assemblages suggest three potential factors that could be responsible for the observed clustering patterns: e.g. salinity differences, latitudinal differences and human population differences. Cluster 2 provided evidence that salinity might play a potential role in separating the species assemblages on the Pacific coast. Although, the ports in cluster 2, Kitimat and Port Alberni, are spatially well separated on the Canadian Pacific coast, they were clustered together. Kitimat and Port Alberni both are known to have low salinity compared to the other ports and the separation of this cluster likely was caused by unique environmental setting in these ports. In the past, salinity had been observed to affect the distribution and survival of intertidal species in coastal regions of North America (Connell, 1972; Mann & Harding, 2003) and it would be surprising that salinity does not influence distribution of species on the Canadian Pacific coast. Latitudinal gradient is another popular explanation for differences in observed species assemblages in both marine and terrestrial systems (Roy et al., 1998). Being separated spatially from other ports might explain its unique community structure observed with cluster analysis. In this chapter, the separations of cluster 3 and 4 suggest latitudinal effects on species assemblage differences on the Pacific coast. Cluster 3, included only sites from Prince Rupert harbour and this port is further north than other ports sampled in this chapter. Similar clustering 52     separation was shown with cluster 4. The ports in cluster 4, Vancouver, Nanaimo and Esquimalt, are located in the same region of coastal British Columbia, southeast Strait of Georgia. Their close proximity to each other in latitude and the connection through the same water body (SoG) might explain high among port similarity in species assemblages compared to other ports on the Pacific coast. Nevertheless, Cowichan Bay, although within the SoG, was excluded from cluster 4 and this cannot be explained with the latitude gradient concept suggesting that could be another variable responsible for the observed clustering. It is possible that human population differences found across the Pacific coast could be an important proxy. The three ports in cluster 4 contained most of British Columbia’s population. The ports harbour three largest cities in coastal British Columbia and have a high degree of human traffic connectedness, via major ferry routes in the lower mainland. It is thus not surprising that urban anthropogenic activities at and near intertidal communities could have influenced the survival of species and contributed to the similarity of species assemblages found in these three ports. The cluster analysis on the Atlantic coast did not demonstrate large scale unique species assemblages across the Atlantic ports. Seven clusters were determined with the analysis of eight ports. This result suggests that on the Atlantic coast, the species assemblage in each port was often port specific. There was one notable cluster, which included the sites from Halifax and Point Tupper harbours. Out of the eight ports examined on the Atlantic coast, these two ports have the highest commercial marine traffic. Like the Invasion index, the similarity of community structure among these two ports could be the result of commercial shipping activities or the long history of the international shipping. Not only were the patterns of species assemblages examined in this chapter, the type of species, native or non-indigenous, that contributed to the differences also were examined. SIMPER analysis revealed the majority of changes in species assemblages on the Pacific coast 53     were due to native species (on average 91% native species). This suggests that either environmental or anthropogenic effects that caused changes in species assemblages of the Pacific coast were affecting mostly native species. NIS were neither promoted nor eradicated in abundance or richness by potential differences in environmental or anthropogenic effects across ports. The results were different on the Atlantic coast as SIMPER analysis revealed the majority of changes in species assemblages were due to NIS (on average 55.5%). This was intriguing because of all species on the Atlantic coast, only six species were non-indigenous. SIMPER analysis revealed that these six NIS contributed 56% to species assemblage change across ports, suggesting that changes in NIS richness or abundance occurred across Atlantic ports. These changes can be due to different patterns of environmental or anthropogenic factors experienced by species at each port. Similar to the Invasion index, these results support the suggestion that low intertidal NIS richness on the Atlantic coast could play an important role in determining species assemblages and community structure within port intertidal habitats. Such prominent role of NIS on the Atlantic coast was not observed on the Pacific coast. Therefore, the noticeable role of NIS on the Atlantic and the lack NIS on the Pacific reinforce the main finding of this chapter that the Atlantic coast was more invaded (and presumably impacted) by NIS than its Pacific counterpart.  2.5 Conclusions This chapter compared the intertidal communities within and between the Pacific and Atlantic coast ports. The objectives were to illustrate patterns of invasion and NIS distributions between the two coasts. The current study introduced the Invasion index to measure the level of invasion. This Invasion index revealed that the Atlantic coast was significantly more invaded by NIS than the Pacific coast. In addition, the Invasion index identified notable ports on the both ends (low and high) of the invasion spectrum but the causes for these differences have not been 54     resolved. Past studies have proposed several hypotheses to explain high levels of invasion, such as the effects of propagule pressure by commercial shipping (Ruiz et al., 1997; Cohen, 1998; Williamson, 1999; Larson et al., 2003; Minton et al., 2005; Colautti et al., 2006). However, these hypotheses are still lacking the quantitative ecological support. Diversity indices also were examined in this chapter. Diversity was shown to be an inconsistent indicator of invasion but results supported the environment-based invasion hypothesis. Ports on the Pacific coast reflected a productive disturbed environment that promoted invasion, while ports on the Atlantic reflected an unproductive disturbed/undisturbed environment. The patterns of NIS diversity found on both coasts suggest that native biological resistance does not play a role in determining the level of invasion, at least in Canadian ports. Environmental effects are likely the most important factors that determine differences shown in the invasion dynamics between the Pacific and Atlantic intertidal ecosystems. This chapter revealed patterns of community structure and NIS distributions that provided better understanding towards invasion ecology, especially at larger spatial scales. Although species distribution patterns were well documented, there are still uncertainties on how these patterns are established and which abiotic variables correlated to these patterns. Whether variables are biotic or abiotic, testing and determining the correlating variables may become a foundation for understanding factors that promote the establishment of intertidal NIS. Several potential variables were discussed that might be either associated or influence the described/observed patterns. These variables included sea surface salinity, latitude, human population and marine commercial activities and further examinations between the patterns observed and variables are required to provide additional information on their effects on the dynamics of intertidal communities. Further studies are needed to examine how the native and non-indigenous species patterns presented in this chapter are influenced. Understanding the 55     abiotic influence towards NIS distribution patterns are needed further improve NIS management in Canadian ports.                                              56     3  EXAMINING ENVIRONMENTAL AND ANTHROPOGENIC VARIABLES ASSOCIATED WITH INTERTIDAL NIS PATTERNS IN PACIFIC AND ATLANTIC CANADIAN PORT COMMUNITIES  3.1 Introduction Non-indigenous species (NIS) have been recognized as the second greatest threat to biodiversity sparking interest among ecologists (Vitousek et al., 1996; Williamson, 1999; Sala et al., 2000; Colautti et al., 2006). The impacts of bioinvasions have reached all regions of the earth, sometimes resulting in catastrophic changes in ecosystems. Ecologists recently have increased their focus on patterns and the causes of NIS establishment with the aim to comprehend the fundamental ecological differences between native and non-indigenous species (Vitousek, 1990; Tilman, 1999; Ruiz et al., 2000a). Ultimately, studying NIS invasion patterns and its causes can be an instrumental tool in discovering new and effective methods for managing future and current NIS arrivals (Hayes, 1998; Bax et al., 2003; Endresen et al., 2004). The increased interest in marine invasion research seems to be positively correlated with an apparent increase in the rate of human or anthropogenic marine activities, either commercial or recreational (Cohen, 1998; Ruiz et al., 2000a; Bax et al., 2003; Minton et al., 2005). There is a common belief that anthropogenic marine activities influence the introduction rate of marine NIS. Historically, scientists tried to understand how organisms were transported by vessels. For example, several studies have recognized that marine organisms can survive in the water systems of vessels (Cohen, 1998; Ruiz et al., 2000a, Bax et al., 2003; Minton et al., 2005; Minchin et al., 2009), in ballast water tanks, and settle on the underbelly of ship hulls (Bax et al., 2003; Minchin et al., 2009). These potential hitchhiking vectors have been proposed as methods for NIS to be introduced around the world. Some common species linked to ballast water introductions include the Chinese mitten crab, Eriocheir sinensis, to Europe in 1912 (Cohen & Carlton 1998; Cohen, 57     1998), the clubbed tunicate, Styela clava, to San Francisco Bay in 1933 (Cohen, 1998; Cohen & Chapmen, 2005), and the purple Mahogany clam, Nuttallia obscurata, to Canada in 1991 (Levings et al., 2002; Dudas, 2005). In addition to these common species, over 75% of current NIS in Australia were assumed to be introduced via hull fouling and 30-40% of current marine NIS in Australia and the Pacific US coast were assumed to be introduced by ballast water; suggesting vessel-mediated vectors play a key role in marine NIS introductions (Cohen & Carlton, 1998; Thresher, 1999; Bax et al., 2003). Numerous other studies have observed the presence of large amounts of living NIS inside vessel-medicated NIS transport mechanisms, such as ballast water tanks and bottom of hulls (Williams et al., 1977; Carlton, 1987; Hallegraeff & Bolch, 1991; Subba Rao et al., 1994). These findings were used to hypothesize that commercial shipping activities are the main vectors for dispersing and introducing marine NIS to new coastal habitats (Ruiz et al., 1997; Cohen, 1998; Cohen & Carlton, 1998; Ruiz et al., 2000a; Larson et al., 2003; Endresen et al., 2004; Minton et al., 2005; Colautti et al., 2006). Although, vessel-mediated introductions are important, there are still many other vectors that could potentially transport NIS to new habitats. These vectors include aquaculture, aquarium trade, and intentional releases (Harding et al., 1994; Bax et al., 2003; Minchin et al., 2009; Sloan & Bartier, 2004). According to the invasion pathway concept, presence of a suitable vector is only one step in the invasion process. Although commercial shipping vectors are the main means of NIS transport and introduction into new environments, the establishment success in these habitats is depends on more than the introduction event. Non-indigenous species can be transported through vectors, but NIS establishment is a function of NIS survival either within the transport mechanism or in the released environment (Hallegraeff, 1998; Bax et al., 2003; Colautti et al, 2006; Lodge et al., 2006). For example, NIS transported in ballast tanks must first tolerate the 58     extreme abiotic conditions inside these tanks. Previous studies have recorded a dramatic decline in the density of organisms in ballast tanks related to changes in temperature (Gollasch et al., 2000), salinity (Gollasch, 1996; Gollasch et al., 2000), photosynthetic rates (Yoshida et al., 1996; Dickman & Zhang, 1999), and oxygen concentrations (Gollasch et al., 2000; Olenin et al., 2000; Wonham et al., 2001). Even if organisms survive the voyage in transport mechanisms (e.g. ballast tanks) and are released in recipient ports, the ability to adapt and compete in a new coastal habitat is the next critical step for NIS establishment (Cohen, 1998; Gollasch et al., 2000; Wonham et al., 2001; Johnston et al., 2009). Combinations of biotic and abiotic conditions are hypothesized to resist NIS introductions. Previous theories have suggested that habitats with rich native diversity have lower possibility for NIS establishment compared to low native diversity habitats (Elton, 1958; Tilman, 1997). Native diversity appears to act as a filter resisting NIS settlement. This hypothesis was first shown in terrestrial ecosystems (Tilman, 1997; Schooler et al., 2006) but rarely has been observed in marine coastal environments. In addition, environmental conditions in native habitats, including a combination of salinity (Mann & Harding, 2003; Powers et al., 2006; Miller et al., 2007), temperature (Stachowicz et al., 2002; Clark & Johnston, 2005; Dafforn et al., 2009), and turbidity (Dafforn et al., 2007) have been shown to affect the establishment success of NIS. Despite survival filters in vectors and new habitats preventing NIS from being transported, settled and established in new habitats, towards the end of the 20th century coastal assessments revealed increasing trends in new NIS introductions in coastal habitats (Bax et al., 2003; Levings et al., 2002; Colautti et al., 2006; Johnston et al., 2009). It has been speculated that increased NIS introductions are linked to the expansion of global commercial shipping: as vessels become larger, travel more frequently and transport more cargo, the ability to transport NIS through commercial shipping becomes more substantial. The speculated link between 59     commercial shipping activities and NIS introductions have laid the foundation to a new hypothesis for NIS establishment called the propagule supply hypothesis (Lonsdale, 1999; Ruiz et al., 2000a; Levings et al., 2002; Drake & Lodge, 2006; Johnston et al., 2009). The propagule supply hypothesis suggests that the high concentration of propagule pressure (a measurement of the amount of NIS individuals released into new habitats) from commercial shipping vectors (e.g. ballast water discharge) may have enough intensity to overcome survival filters in transport mechanisms, in released environment (abiotic and biotic resistances) and other NIS survival barriers that in the past prevented the establishment of NIS to new environments; thus it may speed up settlement and increase establishment success of NIS in new habitats (Cohen & Carlton, 1998; Ruiz et al., 2000a; Ricciardi, 2001; Colautti et al., 2004; Levings et al., 2002). NIS propagules from commercial vessels are shown to be high. On any given day 3,000 to 10,000 species are transported around the world via ballast water (Ruiz et al., 1997; Cohen, 1998; Bright, 1999; Bax et al., 2003; Minton et al., 2005; Johnston et al., 2009). If the propagule supply hypothesis holds true, the greater amount of commercial shipping activities will result in greater propagule pressure from commercial vessels and greater establishment of marine NIS in new habitats. It is thus possible to use propagule pressure from commercial vessels as a proxy for the established NIS in port communities. Developing such proxy may have important implications to invasion management to control propagule pressure from commercial shipping activities (e.g. mid-ocean ballast water exchange that might be more financially feasible than NIS containment and eradication). This chapter will examine variables that may be associated with NIS establishment success in the intertidal zone of Canadian coastal ports. In particular, this chapter will try to better understand what might influence NIS establishment success, their NIS composition, richness or abundance in intertidal communities. The main aims of this chapter are threefold: (a) 60     to examine the relationship between propagule pressure by commercial shipping activities and NIS establishment success; whether commercial shipping activities (ballast water or number of vessel arrivals) can be a proxy for propagule pressure; (b) to identify abiotic variables that influence intertidal NIS establishment success; and (c) to identify abiotic variables that influence intertidal species composition in Canadian ports. This chapter examined the importance of propagule pressure from commercial shipping in coastal intertidal ecosystems and also the abiotic variables that may be an important filter against the establishment of NIS.  3.2 Materials and Methods Detailed procedure for collecting and processing sampled data were mentioned in Chapter 2: Examining intertidal invasion patterns among Pacific and Atlantic Canada port communities. Eight international ports were sampled on each coast. The ports were chosen based on their differences in the intensity of their commercial marine activities (Figure 2-1, Table 2-1). Within each port, six intertidal sites were selected with a total of 96 samples collected and examined for species composition at each port. This was accompanied by measurements of abiotic variables at each site. For each site, GPS coordinates were measured with a hand held GPS unit. Biological parameters To examine potential abiotic factors that might be linked to established intertidal NIS, two categories of biological metrics; e.g. community composition and the Invasion index, were correlated with abiotic variables. The correlations were performed using a multivariate analysis method called Bio-Envir Stepwise analysis (BEST). BEST requires all variables and parameters to be at the same scaling level, scaling level such as site, intertidal zone or port. In this chapter, all biological parameters and abiotic variables were measured or averaged to the site level. Community composition is a qualitative metric representing the species that were found at each 61     intertidal site. The data for community composition were extracted from the species composition dataset presented in Chapter 2. Four community composition variables were created: (a) total species, included all identified species present at each site; (b) native species, composed of only native species present at each site; (c) NIS, comprised from only NIS present at each site; and (d) ballast water discharge influenced non-indigenous species (BNIS), included only NIS with origin linked to ballast water discharge introductions. The Invasion index measured the relative invasiveness in communities by calculating the proportion of NIS abundance in each community (eq. 2-3). Data used to calculate the Invasion index were from the abundance composition dataset in Chapter 2. The Invasion index was calculated for each site in sixteen ports sampled along both Pacific and Atlantic coasts. Abiotic variables There were 12 environmental and anthropogenic variables used in this chapter to correlate with the biological parameters mentioned above. These abiotic variables include commercial marine activities, intertidal sediment, sea surface temperature, and sea surface salinity (Table 3-1). These variables were choices because some of the variables were hypothesized by past studies to have a connection with NIS establishment success in other habitats. Commercial marine activities measured in this chapter included ballast water discharged by commercial vessels and the number of commercial vessel arrivals to each port. Commercial marine activity data were extracted at the port level from the ballast water discharge database provided by Transport Canada. Data were averaged over 2005-2008 and expressed as follows: (a) annual average discharged ballast water by all commercial vessels, (b) annual average discharged ballast water by international commercial vessels only, (c) annual average number of vessel arrivals, and (d) annual average number of international vessel arrivals.  62     Table 3-1. List of abiotic variables used to correlate with NIS establishment success  Variables  Environmental/Anthropogenic  Unit measured  Annual ballast water discharge: Total vessels  Anthropogenic  Kilo-tonnes (kt)  Annual ballast water discharge: International vessels  Anthropogenic  Kilo-tonnes (kt)  Annual vessel arrivals: Total vessels  Anthropogenic  # of vessels  Annual vessel arrivals: International vessels  Anthropogenic  # of vessels  Aquaculture  Anthropogenic  Aquaculture effect score (km-1)  Dock  Anthropogenic  Dock effect score (km-1)  Human population density  Anthropogenic  # of persons  Intertidal slope  Environmental  Meters (m)  Latitude  Environmental  Decimal degree (DD)  Sea surface salinity  Environmental  ppt  Sea surface temperature  Environmental  Degree Celsius (ᵒC)  Sediment  Environmental  Water retention (ml)  63     Since variation in sediment composition among intertidal sites might influence NIS establishment success (Smith et al., 1999; Byre, 2002), the water retention parameter of sediments was measured. Past studies have used other sediment characteristics, e.g. sediment grain size, to show correlations to intertidal NIS composition (Byre, 2002). For this chapter, water retention served as a proxy for sediment composition. The assumption was made that sediment samples with small grain size should have high overall surface area across grains. Thus, sediments with fine particles should allow for higher water cohesion between grains resulting in higher water retention. This chapter hypothesized that different sediment types could influence establishment patterns among NIS. Previous study had suggested that some sediment dwelling NIS have a preference for small grain size sediment, such as mud and sand (Byre, 2002). These types of sediments allow NIS to have greater burial depth, which may decrease inter-specific competition with native species for space and increase the chance of avoiding predators (Smith et al., 1999; Byre, 2002). For example, Mya arenaria, a NIS bivalve on the Pacific coast, were found to have a higher survivorship at burial depths greater than 5 cm (Smith et al., 1999). The critical 5 cm depth prevented the predation by the native crab, Cancer productus, resulting in lower morality of M. arenaria in smaller grain size sediment regions. In this chapter, water retention was used to quantitatively represent different sediment grain size. To measure water retention in sediments, approximately five litres of sediment core were collected from each intertidal level (high, mid and low) at all sites. A polyvinyl chloride (PVC) pipe 30cm in height and 15cm in diameter was used to extract the sediment core. In total, 288 sediment samples were collected on the Pacific and the Atlantic coasts. Approximately 100ml of sediment was randomly extracted from each sample and submerged in 100ml of water for one minute. Before being submerged, the sediment should have been dried to eliminate natural water content from the sample; unfortunately this was not done in this chapter. Sediment was then 64     drained for one minute and the wet weight of the 100ml of sediment was recorded. The sediment was then oven-dried at 60oC overnight and dry weight recorded. Since site level variables were needed for multivariate correlation with biological parameters, sediment water retention from the three intertidal heights were averaged to calculate the average water retention of sediment samples per site. Even though sediment differences were present among intertidal zones, to determine an average for sediment for each site, this chapter assumed that the water retention changes across all three intertidal zones were consistent across all intertidal sites of each coast. Information on sea surface temperature for each port was collected from monthly sea surface temperature datasets of the Coast Watch and SWFSC (Southwestern Fisheries Science Center) environmental research division. The data were extracted from high resolution radiometer sensors from NOAA-17 and NOAA-18 satellites at a spatial resolution of 5km. In this chapter, annual summer sea surface temperatures were used to correlate with biological parameters. Annual summer sea surface temperature for each port was calculated by extracting and averaging data from June, July, and August between 2005 and 2008. Other environmental factors, including latitude, sea surface salinity, and intertidal slope also were measured at each site. Latitude was measured with a handheld GPS unit. Sea surface salinity was measured using a handheld refractometer, while intertidal slope was measured with an inclinometer. In addition to marine commercial shipping activities, other anthropogenic factors were used in correlation analyses. Human population in towns or cities that are associated with each port was used as an anthropogenic factor measure. This chapter hypothesized that ports surrounded by highly populated towns or cities will experience higher disturbances that are linked to pollution and development, e.g. intertidal recreational activities, coastal infrastructure development, and waste disposal, which might influence NIS establishment. Hence, high density 65     ports may lead to higher NIS establishment success and human population may be used as a measurement to represent of human disturbances outside of marine commercial activities that could influence NIS establishment. Population data for each port was extracted from the 2006 Canadian census. Aquaculture sites were another anthropogenic factor measured in this chapter. Aquaculture can hypothetically be another type of propagule pressure that influenced the establishment of NIS, since many aquaculture species are non-indigenous (Ruiz et al., 2000a; Levings et al., 2004). The effect of aquaculture on this chapter was based on the distances between aquaculture sites and sampled intertidal sites, with the assumption that each aquaculture site exerts the same amount of local dispersal effort by aquaculture NIS. Aquaculture sites were determined using GIS (Geographic Information System) data provided by British Columbia Ministry of Agriculture and Land, and Integrated Land Management Bureau in 2005. Since there could be multiple aquaculture sites for each sampled intertidal site, eq. 3-1 was used to calculate a potential effect score that represents both the number of aquaculture sites and the distance between aquaculture and sampled intertidal sites: Aquaculture effect score = ∑ (4.8 / aqdistancen)  (eq. 3-1)  where n is the number of aquaculture sites in each port and aqdistancen is the distance (km) from each aquaculture site to the intertidal site. The constant (4.8) established the maximum distance (480km) aquaculture sites will have NIS effect on intertidal site. For any aquaculture sites, once aqdistancen is at or exceeds the maximum distance, this chapter assumes no effect of NIS from that aquaculture site contributing to the studied intertidal site. The maximum distance and the constant (4.8) were determined by using the potential maximum distance NIS larvae could disperse along the Canadian coast. Past literatures of non-indigenous intertidal species of both Pacific and Atlantic coast of North America found that Nuttallia obscurata, the varnish clam, 66     had the longest larval duration (Larson et al., 2003; Dudas & Dower, 2006). The combination of larval duration, sea surface circulation patterns, and stable environmental conditions estimated the maximum potential dispersal distance of NIS to be 480km (Dudas & Dower, 2006). The equation assumes that as the number of aquaculture sites in the vicinity of the intertidal site increases and the distance decreases, there should be a greater aquaculture effect on intertidal sites. Aquaculture effect scores were recorded only on the Pacific coast since the Atlantic coast had minimal intertidal aquaculture activities near surveyed ports. It also should be noted that the majority of aquaculture activities on the Atlantic coast occurred either with intertidal native species or in subtidal habitats (Grant et al., 1995; Ruiz et al., 2000a; Robinson et al., 2005). Therefore this chapter assumed that aquaculture activities on the Atlantic coast were not a major influence on NIS establishment. Similar calculations were used to illustrate the hypothetical effect of docks in the proximity of intertidal sites. In this chapter, docks are hypothesized to have an effect on the NIS establishment success. These effects could be either due to local intentional and unintentional releases of NIS at docks by human activities, such as animal rights activities, baits releases and sewage disposal. Docks also are areas with heavy intertidal and subtidal human disturbances. Some of these disturbances include pollution and construction, and deconstruction of port infrastructures, which can provide open areas to support new settlement and establishment of NIS. In this chapter, distances between docks and intertidal sites were used as a proxy to represent the dock effect on NIS. Docks were determined using satellite images. They ranged from recreational marinas to berths for commercial ships. The distances between docks and intertidal sites were determined by calculating the distance (km) between the GPS coordinates of docks and adjacent sampled intertidal site. Dock effect score was calculated with the following equation: 67     Dock effect score = ∑ (4.8 / dodistancen)  (eq. 3.2)  where dodistancen represents the distance between each dock and sampled intertidal sites. Data analysis Abiotic variables that could influence establishment success of intertidal non-indigenous and native species in Canadian coastal ports were examined using a multivariate statistical analysis. Unlike, univariate analysis, multivariate analysis allows for correlation with all abiotic variables at one time; taking into account the effects of all abiotic variables on each biological parameter. Correlation analysis used in this chapter was the biological environmental stepwise (BEST) analysis. BEST analysis is an iterative statistical procedure that identifies abiotic variables that are associated closest with biological assemblage patterns observed across communities (Clarke & Gorley, 2006). In this chapter, two BEST analyses were performed based on biological parameters used. First, the Invasion index was used to correlate with 12 available abiotic variables. This analysis was used to determine which variables influenced the relative degree of NIS invasions in intertidal communities of each Canadian port. Second, the different community compositions were correlated with the 12 abiotic variables to identify the closest matching abiotic variables that are associated with each community composition within each port. Again, the four community compositions were total species, native species, NIS, and ballast introduced NIS. The NIS species list can be found in Appendix B. Species that were potentially introduced by ballast water are listed in Table 2-2. BEST analysis was performed through the Plymouth Routines in Multivariate Ecological Research (PRIMER) multi-statistical program. The results are presented as correlation values between 0 and 1 with their corresponding statistical rho and p-values, defined using 999 iterations.  68     3.3 Results Abiotic factors vs. community compositions Significant correlations were found between the community composition variables and combinations of abiotic or human-mediated variables along both the Pacific and Atlantic coasts. On the Pacific coast, sea surface salinity was significantly positively correlated with total (R=0.451; p-value = 0.001) and native (R=0.444; p-value = 0.001) community composition (Table 3-2). A combination of sediments, latitude, salinity, human population, and aquaculture effect score had a significant positive correlation with total NIS (R=0.410; p-value = 0.001) and ballast introduced NIS community composition (R = 0.511; p-value = 0.001) (Table 3-2). On the Atlantic coast, BEST analysis also revealed significant correlations across all community compositions examined (Table 3-3). Jointly latitude, annual average of seasonal sea surface temperature, and sea surface salinity were significantly positively correlated with patterns of total species composition (R = 0.403; p-value = 0.001) and native species composition (R = 0.403; p-value = 0.001) (Table 3-3). In addition, ~ 23% (R = 0.227) of NIS composition across Atlantic sites was explained jointly by a combination of latitude, dock effects, and annual average sea surface salinity (p-value = 0.035).  69     Table 3-2. Significant correlations between abiotic variables and community compositions in intertidal communities of Pacific Canadian ports Community composition  Total  Native  Non-indigenous  Ballast introduced non-indigenous  Correlation  0.451  0.444  0.410  0.511  p-value  0.001*  0.001*  0.001*  0.001*  -Sea surface Salinity  - Aquaculture - Latitude - Human population - Sea surface salinity - Sediment  - Aquaculture - Latitude - Human population - Sea surface salinity - Sediment  Variables  - Sea surface salinity  Table 3-3. Significant correlations between abiotic variables and community composition in intertidal communities of Atlantic Canadian ports Community composition  Total  Native  Non-indigenous  Ballast introduced non-indigenous  Correlation  0.403  0.403  0.231  0.292  p-value  0.001*  0.001*  0.035*  0.040*  Variables  - Latitude - Sea surface salinity - Sea surface temperature  - Latitude - Sea surface salinity - Sea surface Temperature  - Dock effect - Latitude - Sea surface salinity  - Dock effect - Latitude - Sea surface salinity  70     Abiotic variables vs. the Invasion index The Invasion index had no significant correlations with any of the 12 abiotic variables on the Pacific coast. On the Atlantic coast, BEST analysis found the combination of annual average sea surface salinity, latitude, and dock effects score to be significantly positive correlated (pvalue = 0.04, R = 0.292) with the Invasion index (Table 3-3). Commercial shipping variables, ballast water discharge and ship arrivals, had no significant correlation with the Invasion index in the either the Pacific or the Atlantic coast. Patterns of significant abiotic variables On the Pacific coast, the distribution of the five significant abiotic variables (three environmental, two anthropogenic variables) among ports in the Pacific coast are as follows (Figure 3-1): mean sediment water retention across all intertidal sites on the Pacific coast was 30.26 g of water per 100 g of sediment with a range from 6.2 (Campbell River) to 56.8 (Nanaimo). Latitudes ranged from 48.43oN at the southern-most site (Esquimalt) to 54.26 oN at the northern-most site (Prince Rupert). Average sea surface salinity was 19.96 ppt but varied widely between 3.1±0.6 ppt at Kitimat to 30.1±0.4 ppt in Esquimalt. Sea surface salinities at Kitimat (3.1 ppt) and Port Alberni (6.4 ppt) were the lowest among the Pacific ports.  71     Figure 3-1. The distributions of significant abiotic variables with established intertidal NIS in Pacific ports. These include water retention from sediments, latitude, sea surface salinity, human population and aquaculture effects  The anthropogenic variables included human population and aquaculture effect score. Human population size ranged from 8,987 people at Kitimat to 2,116,581 people in Vancouver with the mean of 331,495 people per port. The distribution of human population across all ports revealed that Vancouver has human population orders of magnitude greater than the rest of the Pacific ports. Aquaculture effect scores ranged from 5.9 in Prince Rupert to 73.0 in Campbell 72     River. The distribution of aquaculture effect scores revealed Prince Rupert and Kitimat having much lower aquaculture effect scores than the other Pacific ports. The distributions of the remaining variables are shown in Figure 3-2.  Figure 3-2. The distributions of abiotic variables that were measured in this study but did not show correlation with established intertidal NIS in Pacific ports. These include dock effects, intertidal slope height, ballast water discharge, vessel arrivals and sea surface temperature   73     On the Atlantic coast, the distribution of the four significant abiotic variables is as follow (Figure 13-3): latitude had a narrow range, 43.81ᵒN at Yarmouth - 46.20ᵒN at Sydney. Sea surface salinity revealed a different trend in variation than latitude. Average sea surface salinity across the intertidal sites was 23.3 ppt. It ranged from 12.2 ppt at Sheet Harbour to 32.7 ppt at Yarmouth. Annual average summer sea surface temperature showed a small (14-16.4ᵒC) variation. Dock effects ranged from 0 at Little Narrows to 17.9 at Liverpool. Dock effects at Little Narrows were much smaller than at the rest of the intertidal sites on the east coast. The distributions of the remaining variables are shown in Figure 3-4.  Figure 3-3. The distribution of significant abiotic variations with established intertidal NIS in Atlantic ports. This includes latitude, sea surface salinity, sea surface temperature and dock effects  74     Figure 3-4. The distributions of abiotic variables that were measured in this study but did not show correlation with established intertidal NIS in Atlantic ports. These include ballast water discharge, vessel arrivals, human population, sediments and intertidal slope height  75     3.4 Discussion Propagule pressure and established NIS The main objective of this chapter was to examine if propagule pressure from commercial shipping was related to established NIS in intertidal communities. The propagule supply hypothesis was tested in this chapter with the use of ballast water discharge and the number of vessel arrivals as proxies to represent propagule pressure from commercial shipping. These proxies were analyzed against the distribution patterns of established NIS and the Invasion index. Commercial shipping activities revealed no significant correlation with the two biological parameters within Canadian ports. These results suggest that the effects of propagule pressure associated with commercial shipping activities towards intertidal NIS establishment success were not detectable. Even though commercial vessels are likely the premiere vector for transporting marine NIS into coastal habitats (Ruiz et al., 1997; Cohen, 1998; Cohen & Carlton, 1998; Ruiz et al., 2000a; Ricciardi, 2001; Gollasch, 2002; Larson et al., 2003; Endresen et al., 2004; Levings et al., 2004; Bailey et al., 2005; Minton et al., 2005; Colautti et al., 2006; Ricciardi, 2006) and the effects of propagule pressure might be potentially real, the findings from this chapter and also recent marine community studies suggested that other effects from either environmental conditions or anthropogenic activities outside of commercial shipping might have greater effects that can masked the effects of commercial shipping (Valentine & Johnston, 2003; Clark & Johnston, 2005; Dafforn et al., 2009; Johnston et al., 2009). The lack of importance of commercial shipping activities observed in this chapter towards established NIS was interesting. In the past, the classic theory (propagule supply hypothesis) has supported propagule pressure from commercial shipping activities as one of the most important factors influencing NIS establishment success (Cohen, 1998; Ruiz et al., 2000a; Leung et al., 2004; Minton et al., 2005; Johnston et al., 2009). For example, freshwater 76     ecosystems, such as the Great Lakes, have shown the link between commercial shipping activities and established NIS (Lonsdale, 1999; Bailey et al., 2005; Lockwood et al., 2005; Ricciardi, 2006; Kelly et al., 2009). Through commercial shipping, freshwater species were able to break pass saltwater barrier and released on mass to new freshwater communities in the Great Lakes. There are several potential reasons to explain the lack of correlation between commercial shipping activities and the distribution of established NIS in the marine ecosystems found in this chapter. First, Ruiz et al. (2000a) have discussed difficulties with using spatial distribution patterns of NIS as an overall method to replicate different intensities of propagule pressure from commercial shipping activities. It was noted that conditions for propagules released into new habitats were assumed to be equal across all sites. In other words, NIS must have equal survivorship to the duration of voyages between donor and recipient ports (Ruiz et al., 2000a). In reality, survivorship depends on the travel duration of the commercial vessel, specific NIS life history characteristics, and physical conditions in the commercial NIS transport mechanisms (Wonham et al., 1996; Lavoie et al., 1999; Smith et al., 1999; Ruiz et al., 2000a). These variables may vary drastically across species, vessels, and donor and recipient sites. Thus, based on the earlier assumption, survivorship variations of NIS propagules have been overlooked in this chapter as ports sampled were widely separated latitudinally. For example, Prince Rupert and Esquimalt are approximately 1000 km apart and the distance could influence the correlation between propagule pressure and establishment success in this chapter. Other reasons for not observing an association between NIS propagule pressure and NIS composition may be linked to the differences in time scales between the propagule pressure released from commercial shipping activities and the establishment success of NIS (Essl et al., 2010). A phenomenon called “invasion debt” has emerged in the literature proposing that 77     historical human activities may reflect present day patterns of NIS distribution better than recent human activities. Indeed, the NIS richness patterns of ten taxonomic groups have shown stronger association to human activities in the 1900s compared to the 2000s (Essl et al., 2010). “Invasion debt” appears to be a delayed response of observed NIS richness to past human activities that cumulatively may have influenced NIS establishment success (Pysek et al., 1995; Lockwood et al., 2005; Essl et al., 2010). Thus, it is possible that the propagule pressure measurements in this study for 2005 to 2008 may correlate better with future patterns of established NIS. In addition, the observed distribution of established NIS may correlate better with past measurements of propagule pressure from commercial shipping and the effects of natural secondary dispersal between regions. Therefore due to problems associated with spatial distribution (Ruiz et al., 2000a) and the invasion debt, temporal observations of the propagule pressure and NIS distribution patterns would likely be more informative in examining their relationship than a snapshot of spatial observations (Ruiz et al., 2000a). Localized vectors, such as other measures of propagule pressure, also could be important at individual ports that may mask the effect of propagule pressure from commercial activities. These would include propagule pressure from aquaculture (Ruiz et al., 2000a; Ruiz et al., 2000c; Minton et al., 2005; Haydar & Wolff, 2011), aquarium trade (Whitfield, et al., 2002; Semmens et al., 2004), secondary dispersal through recreational boats (Wyatt et al., 2005; Clarke Murray et al., 2011) or natural dispersal. Previous studies have indicated that aquaculture activities could be viewed as alternative sources of propagule pressure that can have a major influence on the establishment success of NIS (Cohen & Carlton, 1995; Ruiz et al., 2000a; Ruiz et al., 2000c; Minton et al., 2005; Haydar & Wolff, 2011). This is particularly true for the Pacific coast where many non-indigenous marine invertebrates have arrived via shellfish aquaculture/fisheries (Ruiz et al., 2000a; Levings et al., 2004). These aquaculture-introduced NIS, along with their 78     hitchhikers, likely have been restricted to specific regions that favour these activities (Carlton, 1992; Ruiz et al., 2000a). Since these regions were not consistent in the ports studied, the propagule pressure effect from aquaculture activities is not consistent across sampled ports. It is likely that different patterns of propagule pressure from aquaculture activities across the Canadian coast could influence negatively the correlation relationship of propagule pressure from commercial activities and established NIS. In addition to difficulties of observing the importance of propagule pressure from commercial shipping activities, past marine invasion studies have suggested that NIS establishment success might still depend on abiotic conditions. Clark and Johnston (2005) and Valentine and Johnston (2003) experimentally examined effects of propagule success in pelagic environments. These experiments simulated propagule pressure from commercial shipping activities, such as ballast water discharge. The technique involved injecting NIS larval stages, as propagules, into controlled containers to observe their survival; testing if propagule pressure can be a potential measurement for NIS establishment. Instead, NIS establishment success in these studies appeared to be influenced by resource availability (Clarke & Johnston, 2005; Johnston et al., 2009) and physical disturbance of the habitat (Valentine & Johnston, 2003) rather than by propagule pressure. Observational studies in marine pelagic environments also highlighted other factors, outside of propagule pressure from commercial shipping activities that influenced NIS establishment success. A settlement plate survey conducted by Dafforn et al. (2009) found no consistent differences in NIS richness between plates in commercial (high NIS propagule pressure) and non-commercial estuaries (low NIS propagule pressure). Instead, the differences in NIS richness correlated with metal contamination, temperature, turbidity, and pH (Dafforn et al., 2009). Other studies have suggested that salinity (Powers et al., 2006; Miller et al, 2007) and  79     latitude (Roy et al., 1998; Hines & Ruiz, 2000; Connolly et al., 2001) could act as factors contributing to NIS establishment success. Abiotic factors associated with NIS establishment success Abiotic factors (e.g. salinity, temperature) have been shown to influence NIS establishment success in previous studies (Marchetti et al., 2004; Dafforn et al., 2009; Johnston et al., 2009). This chapter revealed that established NIS distribution patterns on the Pacific coast were significantly associated with five variables, including sediment water retention, latitude, salinity, human population, and aquaculture proximity. On the Atlantic coast, the NIS distribution was best described by three variables: salinity, latitude, and dock effects. On both coasts, the common associated environmental variables (salinity and latitude) are well known factors influencing the distribution of intertidal NIS (Hines & Ruiz, 2000; Connolly et al., 2001; Powers et al., 2006; Miller et al, 2007). Effects of salinity on distribution patterns appeared to be species specific. Experimental and observational studies on different NIS have shown that salinity tolerance varies among NIS. For example, on the Pacific coast, the salinity range for Carcinus maenas larvae was 20 to 35 ppt (Mann & Harding, 2003; Hines et al., 2004, DeRivera et al., 2005; Bravo et al., 2007), while the non-indigenous bivalve Mya arenaria have been observed to tolerate salinity ranges of 0-32 ppt (Powers et al., 2006). If establishment was influenced by salinity, communities with different salinity regimes would be expected to have different NIS composition and diversity among sites based on salinity tolerances of the NIS within each community. Latitude also has been identified as a factor influencing NIS establishment. Comparing coastal regions of Alaska, Hines & Ruiz (2000) found significantly lower NIS richness in higher latitudes than lower ones. Several reasons for this relationship were discussed in the previous chapter such as, strong resistance from high latitudinal conditions (Hines & Ruiz, 2000) and an invasion debt event between recent commercial activities and 80     observed NIS establishment (Hines & Ruiz, 2000; Essl et al., 2010). It has been suggested that the strong latitudinal resistance could be driven by low sea temperature in high latitudes (Elton, 1958; Stachowicz et al., 2002; Hellmann et al., 2008). This chapter, however, detected no temperature effect on NIS compositions. This is similar to the San Francisco assessment that found no NIS composition differences between warm and cold water ports (Cohen & Carlton, 1995). It is thus possible that latitudinal variability resistance is linked to other constraints, such as resource availability or dispersal capability (Ruiz et al., 2000a). In addition to salinity and latitude, sediment water retention, which represented sediment types, was also an important factor affecting NIS distributions. In this chapter, correlations of NIS distributions with sediment types (expressed as water retention) were only found on the Pacific coast, where many common intertidal NIS are sediment dwellers, e.g. Batillaria attramentaria, Venerupis philipprinarum and Mya arenaria. Survivorship could be higher for these common intertidal NIS in softer sediments than in coarse sediments, as these species rely on the sediment for shelter and protection. In contrast, the Atlantic coast revealed no relationship between the distributions of NIS and sediment effects. This is because most common intertidal NIS on the east coast live above the sediment surface, e.g. Littorina littorea or Carcinus maenas. Sediment characteristics may not have impeded their establishment success on this coast. Since the anthropogenic histories of the Atlantic and the Pacific coast of Canada are different, it was not surprising to find dissimilar anthropogenic influences that correlated with the NIS distributions on each coast. Different anthropogenic influences on each coast revealed that local vectors of NIS introduction or local dispersal are more important than large scale global vectors, such as commercial shipping. This chapter revealed that aquaculture and human population density were closely related to NIS distributions on the Pacific coast of Canada. It is obvious that the aquaculture effect is more prominent on the Pacific coast than on the Atlantic 81     coast mainly due to differences in cultured species: Pacific – mostly NIS such as Crassotrea gigas and Venerupis philipprinarum (Brye, 2002; Levings et al., 2004), Atlantic – mostly native species such as Mya arenaria, Crassostrea virginica and Mercenaria mercenaria (Ruiz et al., 2000a; Robinson et al., 2005). The correlation with aquaculture suggests that the variability in NIS composition within intertidal communities could be linked to local dispersal of NIS from nearby farms. Several studies have discussed the relative importance of aquaculture to NIS establishment (Ruiz et al., 2000a; Bax et al., 2005; Minchin 2007). Studies conducted in USA and Australia showed similar percentages of NIS introduced through ballast water discharge and aquaculture (Bax et al., 2005). In addition, cultured NIS may be responsible for the introduction of hitchhiking organisms (Eldredge, 1994; Relini & Trochia, 2000; Minchin 2007). Fouling species such as Sargassum muticum could be transported on aquaculture gear, while parasites and viruses could hitchhike on infected specimens and spread in their new environments through aquaculture-related activities (Bax et al., 2003). It is harder to interpret the relationship between NIS distributions and human populations on the Pacific coast or dock effect scores on the Atlantic coast. This chapter assumed that these activities were proxies for human disturbances. Past studies have suggested that human disturbances open up more space for NIS to settle and become established (Valentine & Johnston, 2003), while others have proposed that human disturbances decrease the biological resistance of native species, easing NIS establishment (Von Holle & Simberloff, 2005). More in depth studies are urgently needed to understand how specific human disturbances affect the establishment of intertidal NIS. The available abiotic variables also were compared to patterns of the Invasion index along each coast. The Invasion index was used as a proxy to represent NIS establishment success based on relative NIS and native abundance. The results revealed no significant association with 82     any of the 12 variables along the Pacific coast. The absence of the correlation on the Pacific coast can be explained by the high NIS and native species diversity in the region. To calculate the Invasion index, all NIS were generalized as an overall group. However, since each NIS can be influenced by different abiotic variables, an ecosystem with high NIS diversity (e.g. Pacific coast) also could have high variation in variables that could influence NIS establishment success and relative population sizes. By using the Invasion index and generalizing all NIS into one group, the unique variables influencing each species likely will be overshadowed, resulting in no correlations between the Invasion index and abiotic variables. In contrast, significant correlations with abiotic variables were found with the Invasion index on the Atlantic coast. The Invasion index was significantly correlated with salinity, latitude, and dock effects. One explanation that the Invasion index can work as a proxy on the Atlantic coast is that the Atlantic coast has relatively low species richness and diversity (six NIS found in total). The overall low richness and diversity result in low variations in the species composition between communities. Therefore, using the Invasion index, a method that generalized all NIS into one meta-species, as a proxy to correlate with abiotic variables is possible. The results from using the Invasion index as a proxy correlation on the Atlantic coast mirrored the same significant variables found with using NIS compositions as an indicator of NIS establishment success. This chapter suggests that due to the low species richness on the Atlantic coast the same abiotic variables that promoted the establishment of NIS on the Atlantic coast could also promote them to thrive or increase in abundance in new intertidal regions. Overall, this chapter demonstrated that commercial shipping activities, which can represent propagule pressure from commercial shipping, have no detectable influence on the established intertidal NIS in port communities. Even though previous hypotheses have suggested that commercial shipping and its propagules have the ability to bypass survival filters and promote 83     establishment, this chapter proposes that environmental factors still act as filters to determine the establishment of NIS. Among anthropogenic influences, localized vectors, such as aquaculture, appear to have a better correlation with the established NIS than commercial shipping vectors. Abiotic factors associated with total and native establishment success In addition to correlating variables with NIS establishment success, variables associated with total and native establishment success also were studied. On the Pacific coast, salinity affected both total and native species compositions, while on the Atlantic coast, in addition to salinity, latitude and temperature also were found to be important. It appears that the total, native and NIS establishment success were dependent on similar (but not the same) combinations of abiotic variables on either coast. This demonstrated that total species composition of both the Pacific (high NIS diversity) and Atlantic (low NIS diversity) intertidal communities is related to native species composition even though the Atlantic coast had an over abundance of NIS. A closer look into the specific variables associated with total and native species composition revealed that all associated variables were environmental variables. Unlike NIS composition, the composition of total and native species in intertidal port communities were not influenced significantly by anthropogenic activities despite the notion that Canadian ports are assumed to have the greatest, persistent anthropogenic disturbances in marine ecosystems. This was an unexpected result as invasion ecology theories have proposed anthropogenic disturbances to be the main drivers of community restructuring (Lockwood et al., 2005; Von Holle & Simberloff, 2005). Although this was counter intuitive, similar results are not uncommon. Studies have compared pristine and commercial estuaries and found no significant differences between total species compositions (Dafforn et al., 2009) suggesting that overall species compositions are largely determined by environmental variables (Dafforn et al., 2009; Johnston et al., 2009) as was shown here. 84     3.5 Conclusions This chapter examined factors associated with NIS establishment success within intertidal communities of Canadian ports. Commercial shipping activities revealed no significant relationships with intertidal NIS establishment success in Canadian ports. However, this chapter found that NIS establishment success may be affected by sediment type, latitude, salinity, aquaculture, and human population density on the Pacific Coast, and salinity, latitude, and human commercial port disturbances on the Atlantic coast. Our results imply that propagule pressure from commercial shipping appeared to be not as important as identified in previous studies and likely only have a historical significance. Instead, this chapter showed that established NIS were influenced by specific local activities rather than a large scale global vector (commercial shipping). Human disturbances expressed as population density and aquaculture effects on the Pacific coast and dock effects on the Atlantic coast, were found to be significantly associated with NIS compositions. Future research is needed to understand the importance of small local vectors and to determine specific human disturbances that influence the establishment success of intertidal NIS. In addition, environmental variables appeared to be strong filters in preventing and influencing NIS establishment in intertidal communities. Further programs on prevention and management of NIS should reconsider the importance of survival filters as an efficient ecosystem system service in resisting NIS invasions. Although anthropogenic activities have been linked to NIS establishment success on both coasts, they did not have any direct association with the overall composition of intertidal species in Canadian ports. This chapter confirmed that environmental variables, such as salinity, sea surface temperature, and latitude (a proxy of climate or geographic differences) should still be regarded as the main drivers determining the biological community composition in coastal intertidal systems. Nevertheless, it should be noted that anthropogenic activities may affect many 85     critical environmental variables, including salinity and sea surface temperature and thus could indirectly shape these communities.  86     4  GENERAL DISCUSSION For the first time, large-scale NIS distribution patterns along the Pacific and Atlantic  coast of Canada have been obtained through this thesis. Moreover, abiotic variables, both anthropogenic and environmental, that are associated with established NIS were reviewed. An intertidal study at such national scale provided a consistent and comparable overview of the distribution of both native and non-indigenous species. This allowed accurate inter-comparisons between two Canadian coasts, intra-comparisons within each Canadian coast, as well as the establishment of commonalities and/or specifics in NIS invasion and establishment. The findings of this study were consistent with the ”Environmental based hypothesis” postulating that NIS establishment is mainly environmentally driven, while biological interactions with native species may play a secondary role. This suggested that the NIS and native diversity should have similar trends (Huston, 2004). The two studied Canadian coasts presented different ends of the hypothesis spectrum. Pacific intertidal port communities reflected the result of NIS establishment under diverse environmental conditions and high native diversity leading to high NIS diversity. In contrast, Atlantic communities appeared to be exposed to poor environmental conditions that result in low native and NIS diversity. Consistent findings using large scale surveys suggested that the environmental based hypothesis may be generalized and/or extrapolated across intertidal communities in other ports. As a consequence, this thesis provided a solid baseline for future studies to examine the environmental based hypothesis worldwide.  4.1 Species Distribution This study demonstrated that environmental conditions influencing intertidal communities of Pacific and Atlantic ports can be dissimilar enough to cause specific distributions of native and non-indigenous species. Species richness, diversity and the Invasion index each showed that intertidal communities were different between the two coasts. The 87     Invasion index specifically demonstrated that intertidal communities on the Atlantic coast were more invaded than the Pacific coast. This pattern conforms to previous CAISN (Canadian Aquatic Invasive Species Network) assessments of the risks in port communities based on different aspects of ballast water transport (Briski et al., submitted). Briski and colleagues compared various vector strength indices (e.g. abundance of species inside ballast tanks, invasion risk of transoceanic vs. coastal voyages) across Canadian commercial shipping regions (Pacific coast, Atlantic coast and the Great lakes) and suggested that invasion risks from ballast water discharge were greatest on the Atlantic coast (Briski et al., submitted). Interestingly, the results from the Invasion index presented in this thesis, which is based on the overall NIS compositions at each community and not related to commercial shipping vector strengths, support their conclusion. The Invasion index showed that the intertidal communities on the Atlantic coast were subjected to a greater ratio of established NIS than on the Pacific coast. This thesis found significant differences in richness, diversity and patterns of invasion, even though the two coasts are at similar latitude and located in the same country. Several reasons may be explored to explain these differences. It has been proposed that outside of anthropogenic activities, natural dissemination by historic biogeography is usually the “default” explanation for the distribution of species across regions (Carlton, 1987; 2003). Fundamentally, different species composition between two regions can be explained by their historic biogeography. One example that had been discussed to demonstrate the differences in historical biogeography that could fundamentally affect the composition of intertidal communities is the exposure of these communities to glacial retreats (Carlton, 2011). The Cordilleran ice sheet from the Pacific coast retreated from the Fraser lower mainland and the Strait of Georgia > 12,000 years ago (Clague & Turner, 2003). This glacial retreat exposed fertile intertidal habitats to the settlement and establishment of new arrivals. Fossils of intertidal species, such as native 88     bivalves, can be dated back to 12,000-14,000 years ago (Clague & Turner, 2003). This length of time of exposed intertidal habitat allowed not only re-settlement of species but also evolution and divergence that created diverse and species rich communities on the Pacific coast. On the other hand, the Laurentide ice sheet that covered most of Canada including the Atlantic coast retreated to expose poor rocky conditions. Carlton had suggested that low species richness in the Atlantic coast is due to the exposed poor rocky condition; re-settlement of species become more difficult under these conditions (Carlton, 2011). Another common biogeography aspect that explains the dissimilarity in species composition between the Pacific and the Atlantic coast of Canada is differences in regional climate. Most of the Pacific intertidal communities surveyed in this thesis are located in a temperate rainforest region. The warm airstream from the Pacific Ocean is trapped in this region by the Rocky mountain chain, resulting in the most temperate climate in Canada. Because of this temperate environment, biological organisms are allowed to flourish year–round, achieving rich species diversity. On the other hand, intertidal communities in the Atlantic coastal region of Canada have a more rugged and variable climate that is seasonally affected by Arctic and Maritime air flow into this region. Variable climates exposed organisms to a hostile environment preventing them from flourishing and leading to lower species richness in this region. One example of hostile environment in the Atlantic intertidal communities is ice scouring in the winter. Below freezing temperature and the presence of ice sheet in intertidal communities during the winter months create conditions that are not suitable for wide range of species richness to exist. The few species that were able to establish in such rugged environments are assumed to have broad environmental tolerances. The difference in climates is probably the most common cause explaining the species composition variation between intertidal communities of the Pacific and Atlantic coasts. Other oceanic and coastal productivity dynamics also can be 89     considered to explain for the high species richness and diversity observed in the Pacific verses the Atlantic. The Canadian Pacific coast is located in the eastern side of the Pacific Ocean. It is commonly believed that eastern side of oceans hold more species diversity than their western counterpart due to productivity from mountain chain runoffs or from upwelling events and similar ocean margin dynamics. Whereas the Canadian Atlantic coast is located in the western side of the Atlantic, thus experiences less productivity from common ocean and coastal dynamics.  4.2 Propagule Pressure from Commercial Shipping One of the main objectives in this study was to examine the propagule supply hypothesis in marine ecosystems. This hypothesis suggested that a high magnitude of propagule pressure, such as from commercial shipping activities, can overcome environmental filters that reduce the establishment success of many NIS. The findings from this study showed no significant relationships between propagule pressure from commercial shipping activities and the distribution of established NIS in intertidal communities of Pacific and Atlantic ports of Canada. This study found that distributions of the established NIS are significantly related to environmental and anthropogenic activities, excluding commercial shipping activities. In addition, there are indications that ballast water discharge and vessel arrivals, the measures currently used to represent propagule pressure from commercial shipping activities, should not be applied as a proxy for propagule pressure. For example ballast water discharge represents the potential propagules released into new environments, including both live and dead NIS. Of the potential propagules, only live propagules (actual propagules) can contribute to the establishment success of NIS. By measuring potential, rather than actual, propagule pressure, such as ballast water discharge, it would be difficult to predict NIS establishment success. Actual propagules are limited by environmental variables inside the ballast tanks, including oxygen, temperature, 90     and salinity, which are known to deteriorate in quality over time (Gollasch, 1996; Dickman & Zhang, 1999; Gollasch et al., 2000; Olenin et al., 2000; Wonham et al., 2001). Indeed, transoceanic samplings performed by the CAISN Program have clearly established that actual propagules are negatively correlated with the age of ballast water (Humphry, 2008). Measuring only potential propagule pressure will not be able to account for effects of ballast water age on the survivability of actual propagules. In addition, Canada’s mid-ocean exchange (MOE) program for most international commercial vessels should dramatically affect actual propagules and vessels subjected to MOE have shown significantly lower actual propagules than intracoastal non-MOE ships (Humphry, 2008). Both, water aging and MOE effects should thus be properly quantified to obtain/predict actual propagule pressure that could be used as an accurate proxy for the NIS establishment success. Even though this study did not find any significant correlation between propagule pressure from commercial shipping and established NIS, commercial shipping cannot be neglected as an efficient vector for transporting and influencing the establishment of NIS in new regions. Actual propagules inside ballast tanks have continued to be shown to be diverse and abundant in invasion vector studies (Williams et al., 1977; Hallegraeff & Bolch, 1991; Humphry, 2008; Briski, 2011). The correlation in this thesis could not link commercial shipping with established NIS, but significant links with established NIS were found with other local vectors, suggesting that local vectors might be more prominent in determining NIS establishment and distribution patterns. Local vectors, such as aquaculture and secondary local dispersals (recreational boat or natural dispersal), have been shown as effective mechanisms for the NIS establishment (Ruiz et al., 2000a; Wyatt et al., 2005; Faasse & Ligthart, 2009; Haydar & Wolff, 2011). In this study we found that local vectors, such as aquaculture activities on the Pacific coast and human disturbances outside of commercial shipping activities on the Atlantic coast, are 91     contributing factors for the intertidal established NIS in Canadian ports. It appears that these local vectors may operate at different spatial scales compared to commercial shipping activities and thus could distort relationships between the NIS establishment and propagule pressure from commercial shipping.  92     5  CONCLUSION Commercial shipping activities, such as ballast water discharge and shipping arrival  frequency, appeared to be unimportant in influencing intertidal NIS establishment success in Canadian ports. This thesis characterized the distribution of intertidal NIS and native species in Canadian ports along both the Pacific and Atlantic coasts and found that the distributions of both NIS and native species were significantly different between the two coasts. The distribution patterns agreed with the environmental based invasion hypothesis suggesting that environmental conditions are the main reason for observed distribution patterns of both NIS and native species. NIS distribution was not influenced by the biological resistance from native species. A novel Invasion index for the comparison and assessment of the invasion level in communities has been introduced. The Invasion index revealed that the Atlantic coast was more invaded than the Pacific coast. Although the Invasion index can be used to assess community invasion, our findings showed that this index did not provide consistent results when it was used as a proxy for NIS establishment success. Previous studies have shown that commercial vessels transport large quantities of NIS into new regions. It was initially conceived that the high magnitude of potential propagules from commercial shipping activities, such as ballast water discharge, can produce enough propagules to influence the establishment success of NIS. However, our study has found no significant correlations between propagule pressure from commercial shipping activities and established NIS. The latter were found to be significantly associated with 1) environmental variables that also influenced the distribution patterns of native species, and 2) anthropogenic activities that are localized in specific regions. Our findings demonstrated that established NIS are still influenced by environmental variables, therefore suggesting that environmental filters are still at play preventing NIS establishment. This thesis also has demonstrated that local (small scale) activities might have a greater influence on establishment success than previously 93     realized. These variables were previously largely neglected or ignored due to globalization. In order to properly understand invasion processes, evaluate risks, and predict and manage future invasions, it is important to have a clear understanding of all the stages of the invasion pathway (Figure 1-1). This thesis has shown that the effect of Stage 2 (e.g. NIS release) cannot be directly linked to Stage 4 (e.g. established NIS distribution). Other stages (e.g. environmental filters) are important in influencing NIS establishment. Future research should focus towards understanding not only commercial shipping as a vector but also other local vectors that have static, but effective, influence on NIS establishment success as well as environmental resistances that can prevent NIS settlement and spread. Follow up studies should lead to a different NIS management approach that would refocus from anthropogenic preventions towards protecting abiotic conditions that can self-resist the settlement and establishment of NIS in new regions. Lastly, this thesis provided a novel method for invasion assessment (the Invasion index). This index should be integrated in future invasive studies to further strengthen its credibility and provide for future development. The simplicity of the Invasion index may provide a method of assessment that had been problematic for many invasion studies in the past.  94     REFERENCES Allen, F.E. (1953) Distribution of marine invertebrates by ships. Australian Journal of Marine and Freshwater Research, 4, 307-316. Alpine, A.E. & Cloern, J.E. (1992) Trophic interactions and direct physical effects control phytoplankton biomass and production in an estuary. Limnology and Oceanography, 37(5), 946955. 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Yoshida, M., Fukuyo, Y., Murase, T. & Ikegami, T. (1996) On-board observations of phytoplankton viability in ships’ ballast water tanks under critical light and temperature conditions. Harmful and toxic algal blooms. Intergovernmental Oceanographic Commission of UNESCO (ed. By Yasumoto, T., Oshima Y. and Fukuyo, Y.), 205-208. UNESCO, Paris.                                       112     APPENDICES Appendix A: The Invasion Index () The Invasion index evaluates the degree of invasion within a community by measuring the relative abundance of NIS. The calculated relative abundance of NIS can be used to speculate the effect of invasion to the community. This effect could be NIS domination over native species for limiting nutrient resources (Parker et al., 1999) or for limited space. Relative abundance can be either the relative number of non-indigenous individuals, relative percent cover of NIS in a given area or the relative biomass of NIS in a given area (Parker et al., 1999). The Invasion index (eq. 2-3) calculates the NIS dominance by using a modification of the equation for Simpson’s diversity index (eq. 2-2), where i represents the total relative abundance of NIS in the community. Similar to the Simpson’s diversity index, N denotes the relative abundance of total species in the community. In the case of communities with cryptogenic species, species with unknown status (native or NIS), a modification of the Invasion index is provided (eq. A-1): c = [(i + ½ c) x ((i + ½ c) -1)] / [N x (N-1)]  (eq. A-1)  where these “c” species are not treated as native (i.e., no potential impact) nor non-indigenous (i.e., assumed negative impact).  can be interpreted as the probability of randomly choosing two individuals from a given area and having both of those two individuals be NIS or more simply the probability of encountering a non-indigenous individual in a community. While Simpson’s diversity index measures the sum of abundance dominance for each species (Simpson, 1949), the Invasion index sums all NIS individuals and measures the dominance of all NIS as a group. The Invasion index ranges between 0 and 1, where 1 would be a community where all individuals are nonindigenous and 0 when none of the individuals are non-indigenous. This index is used to compare across communities to determine how invaded one community is compare to another. 113     In addition to relative degree of invasion, a reference point of 0.25 is established for the Invasion index in this study, where NIS abundance is equal to the native species abundance. This reference point is a threshold for invasion. When the Invasion index is greater than 0.25, invasion becomes progressively greater on the community, since the slopes of the Invasion index steepens with each additional NIS abundance is added to the community. When the index is lower than 0.25, invasion effect on community is not as apparent (Figure A-1), as the change of slope with each additional NIS abundance does not drastically change the Invasion index. It was difficult to speculate for an invasion threshold for the Invasion index, since past invasion studies have shown both positive (Alphine & Cloern, 1992; Schooler et al., 2006) and negative (Cleland et al., 2004; Sanchez et al., 2005; Gremmen & Smith, 2008) responses to native community with high non-indigenous abundance. Instead of extracting a specific number as a threshold from these studies, these studies demonstrated that changes (positive or negative) in productivity, richness, abundance and abiotic resources do occur with a “dominant” abundance of NIS in the community. This dominance in NIS abundance ranged from 60 – 85% dependent of the study. Since there is such a broad range to define dominance, the Invasion index used in this study assumes that NIS dominance range starts at 50%, resulting in the reference point 0.25. This reference point is set for this specific study, it can change based on specific communities or until further evidence can propose a higher or lower reference point is needed.  114     Figure A-1. The Invasion index model, where N = 100. Reference point is specified at 0.25. When the index is above this reference point, invasion effect becomes progressively greater towards the community. When the index is lower than this reference point, invasion effect are suggested to be not apparent towards the community  As mentioned earlier, the Invasion index can be calculated using either biomass, individuals or percent cover. When dealing with the number of non-indigenous individuals, species of different sizes makes it more difficult to compare the impact of a single large invader compared to multiple microscopic invaders. Calculating the Invasion index with biomass can incorporate the size differences between species and still be used to measure invasion impact with the Invasion index. There should be caution in using relative biomass for the Invasion index. An appropriate unit of biomass should be used in the calculation. With biomass, Invasion index implies the probability of picking two unit of biomass from the community and both units  115     of biomass are NIS. If the units were too small or too large, the Invasion index could be dramatically over or underestimated.  116     Appendix B: List of Non-indigenous Species List of non-indigenous found in the Pacific and Atlantic coast based on their port locations. Possible introduction by ballast water discharge is denoted by *. Non-indigenous species  Ports found in  Coast found in  Alcyonidium gelatinousm*  Esquimalt, Vancouver  Pacific  Ampithoe valida*  Campbell River  Pacific  Balanus improvisus  Esquimalt  Pacific  Batillaria attramentaria  Campbell River, Esquimalt, Nanaimo  Pacific  Botrylloides violaceus  Esquimalt, Nanaimo  Pacific  Caprella mutica*  Campbell River  Pacific  Caprella simia  Esquimalt  Pacific  Crassostrea gigas  Campbell River, Cowichan Bay, Esquimalt, Nanaimo, Port Alberni, Vancouver  Pacific  Didemnum vexillum  Campbell River  Pacific  Monocorophium uneoi  Cowichan Bay, Kitimat, Vancouver  Pacific  Mya arenaria  Cowichan Bay, Esquimalt, Kitimat, Nanaimo, Port Alberni, Prince Rupert, Vancouver  Pacific  Nephtys caeca  Prince Rupert  Pacific  Nuttallia obscurata*  Campbell River, Cowichan Bay, Esquimalt, Nanaimo, Port Alberni, Vancouver  Pacific  Pseudopolydora kempi*  Vancouver  Pacific  Ptilohyale littoralis*  Campbell River, Vancouver  Pacific  Sargassum muticum  Campbell River, Esquimalt, Nanaimo, Vancouver  Pacific  Sigambra tentaculata  Campbell River  Pacific  Urosalphinx cinerea  Campbell River  Pacific  117     Non-indigenous species  Ports found in  Coast found in  Venerupis philippinarum  Campbell River, Cowichan Bay, Esquimalt, Nanaimo, Port Alberni, Vancouver  Pacific  Zostera japonica  Campbell River, Cowichan Bay, Kitimat, Nanaimo, Port Alberni, Prince Rupert  Pacific  Carcinus maenas  Halifax, Liverpool, Point Tupper, Sheet Harbour, Shelburne, Sydney, Yarmouth  Atlantic  Codium fragile  Point Tupper, Shelburne  Atlantic  Fucus serratus  Halifax, Liverpool, Point Tupper, Sheet Harbour, Shelburne, Sydney, Yarmouth  Atlantic  Littorina littorea  Halifax, Liverpool, Point Tupper, Sheet Harbour, Shelburne, Sydney, Yarmouth  Atlantic  Membranipora membranacea  Halifax, Point Tupper  Atlantic  Ostrea edulis  Sydney  Atlantic       118     

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