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Intertidal community structure, dynamics and models : mechanisms and the role of biotic and abiotic interaction

University of British Columbia

This study is a comprehensive and experimental approach to understand the dynamics producing structure in an intertidal algal community. Both biological factors (competition and herbivory) and physical factors (disturbance and physical stress) were investigated through field manipulative experiments, non-manipulative monitoring and laboratory experiments for the last 3 years in Barkley Sound, Vancouver Island. The community studied contains three dominant perennial macroalgae, Mazzaella cornucopiae (Rhodophyta), Fucus distichus and Pelvetiopsis limitata (Phaeophyta), and some ephemeral algae as well as coexisting invertebrates such as barnacles, limpets and snails. Biological interactions and their mechanisms for all these organisms turned out to be complicated and non-hierarchical interaction networks which include reversal of dominance and indirect interaction. There was evidence for both negative and positive interactions existing between the same pair of species. Competitive dominance was changed depending on the developmental stages of the competitors and due to differences in morphology, and also the outcomes of interactions were modified by physical stresses (i.e., desiccation and wave action). Snails preferentially grazed the red alga, and limpets reduced the abundance of the ephemeral algae (the early colonizers) which otherwise inhibited the settlement of the later successional species such as the fucoids. Barnacles facilitated the colonization of Fucus and ephemeral algae after disturbance. Responses of the three dominant algae and ephemerals to the different sizes and time of disturbance were species-specific and depended on the alga’s life history and reproductive characteristics. The study shows that both the biological and physical factors influenced the structure of this community, and that the non-hierarchical interactions among the major species and their well-balanced responses to disturbance support a high likelihood of maintaining the current diversity in this algal community.

Thesis/Dissertation

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2009-04-15

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http://hdl.handle.net/2429/7148

Botany

University of British Columbia

UBCV

DSpace