Note changed week day—Friday, 10 October
Irene Gregory-Eaves
McGill University
Ecological dynamics of sockeye salmon nursery lakes across large spatial and temporal scales
Abstract
The annual return of anadromous salmon pulse nursery lakes with nutrients, which, in turn, can play a primary role in structuring resident aquatic communities. The magnitude of this nutrient pulse and its impact on resident freshwater communities, however, varies considerably across the spectrum of sockeye salmon nursery lakes that exist. Over the past few years, colleagues of mine and I have been conducting analyses over spatial and temporal gradients to define the significance of salmon-derived nutrients in sedimentary organic matter and in shaping diatom and zooplankton communities. Based on a large spatial survey of lakes, we have found that salmon spawner density is the single-most important predictor of δ15N, a tracer often used to infer inputs of salmon-derived nutrients. In coastal lakes, however, elevated amounts of precipitation lead to faster flushing rates and can bring in larger loads of terrestrially-derived organic matter, which dampen the salmon-derived nutrient signal. As such, we are focusing our efforts on nursery lakes found within relatively low to moderate precipitation regions (i.e., receiving less than 2–3 m of rain annually). In particular, we have been studying the dynamics of primary and secondary producers that are preserved in sediment cores from a series of lakes that represent a modern salmon density gradient. Based on this network of lakes, we have found that beta-diversity, quantifying diatom species turnover over the past ~300 years, is related to average sedimentary δ15N. The fossil zooplankton community is much less species-rich, but interesting dynamics are apparent in production trends and their interaction with other trophic levels. Overall, our research is building a better understanding of the functioning and dynamics of sockeye salmon nursery systems; knowledge that can be used to both draw stronger inferences from lake sediment records as well as help to manage sockeye salmon populations in a sustainable fashion.
Bio
Rene Gregory-Eaves is an Assistant Professor in the Dept. of Biology at McGill University. Although now living in central Canada, her salmon research allows her to make an annual migration back to her nursery habitat, the West Coast.
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