UBC Theses and Dissertations
Effects of log storage on physical habitat, water quality, benthic invertebrates, and metal contaminants in the Fraser River estuary Kussin-Bordo, Noah S.
To facilitate the movement and processing of timber in some regions of the Pacific Northwest, bundles of logs are tied together to form large rectangular rafts (also known as booms) which are transported and stored in aquatic environments. In the lower Fraser River, some reaches have > 50% of their shoreline with adjacent log booms, yet our understanding of the effects of log storage on aquatic habitats and biota is very limited. The objectives of my thesis were to examine key environmental characteristics that may be affected by log storage activities in the lower Fraser River and estuary. I sampled water and sediment at control, current log storage sites, and former log storage sites and investigated: metal contaminant concentrations, water quality (pH, temperature, turbidity, total dissolved solids, and oxygen concentrations and saturation), invertebrate diversity, biomass and abundance, vegetation coverage, and sediment compaction. I found that at most sites with current log storage, they had compacted sediments and reduced vegetation coverage, effects that are likely caused by logs ‘grounding’ onto the benthic environment due to tidally influenced changes in water level. I found that bottom water pH was lower, and surface temperatures cooler, at current log storage sites, but found no other differences in water quality or in metal contaminants, among log storage categories. Median abundance of total benthic invertebrates was 4.26 times lower at current log storage sites relative to control sites, potentially attributed to log grounding and poorer water quality in their benthic habitats. Diptera were most abundant and Haplotaxida least abundant at control sites. Unfortunately, lack of reliable data on when logs were moved onto and off of sites made it impossible to confirm the ‘time since fallow’ for former log storage sites. Thus, interpreting results from former sites was difficult, and assessing the potential ‘recovery’ from log storage was not possible. While the presence of log booms on nearshore environments may have some effects on water quality, the largest effects seem to come from logs grounding on the substrate which changes the physical habitat. The fact that log booms are coming into contact with, or resting on the substrate, is in direct contradiction with known best management practices for log storage which state that at no time should logs and substrate come into contact.
Item Citations and Data
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