Impacts of shellfish aquaculture on marine vegetation
Marine vegetation, such as seagrass and seaweeds, form the foundation of many nearshore ecosystems and are considered critical habitat for many ecologically and economically important species. Shellfish aquaculture has the potential to impact marine vegetation in a variety of ways: via waste particles smothering vegetation; increasing water clarity affecting light penetration (thereby enhancing growth of marine vegetation); and eutrophication (fuelling growth of epiphytes which compete with the seagrasses). While the range of effects of shellfish culture on marine vegetation can be complex, our understanding of the interactions between them is limited. Determining the impact that shellfish farms may have on marine vegetation had been identified as a priority research area on Canada's West Coast.
Baynes Sound, British Columbia is an area of intensive shellfish aquaculture making it an ideal location for this research. In addition, data on the oceanography, plankton and benthic communities in Baynes Sound had been collected for several years. This project evaluated changes in marine vegetation and associated communities by measuring the relative biomass of each trophic level (grazing, predatory, invertebrates and fish) along a gradient of effects from intensive shellfish aquaculture. This approach provided a quick assessment of ecosystem-level effects that may be induced from shellfish aquaculture activities.
Project results provide aquaculture managers with information that will help with decision making to establish appropriate carrying capacity for shellfish tenures, as well as to develop management plans with the goal of reducing environmental impacts from shellfish aquaculture.
Patterns of seaweed biomass cascaded up though grazer, consumer and predatory trophic levels. However, the distribution and abundance of seaweed across sites in the sound did not reflect the nutrient gradient of the sound. These results suggest that the communities associated with foundational nearshore seaweed are vulnerable to disturbances in the abundance and distribution of seaweed. Nevertheless, it does not appear to be a function of large scale nutrient patterns in Baynes Sound.
Stewart, H.L. and Piercey, G.E. 2013. An examination of marine vegetation communities and the trophic communities they support in Baynes Sound British Columbia. Can. Data Rep. Fish. Aquat. Sci. 1248: iv +29 p.
2012 - 2014
Terri Sutherland, Research Scientist, Fisheries and Oceans Canada, Pacific Region
Beth Piercey, Fisheries and Oceans Canada, Pacific Region
Steve Katz, National Oceanic and Atmospheric Administration, Channel Island National Marine Sanctuary
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