Tracing prey sources from the base of the food web to understand drivers of pelagic nutrition

Speaker: Dr. Anna McLaskey, Research Associate, IOF Pelagic Ecosystems Lab

Nutritional quality of prey influences consumer communities including their nutritional quality, so shifts in nutrition at the food web base can be transferred up the food chain to affect fish, seabirds, and mammals. Zooplankton are the main link between primary producers and higher trophic levels, and display variable nutrition based on their taxonomy, prey sources, and physical environment. Therefore, zooplankton nutritional quality and its drivers are key to understanding how nutrition influences pelagic food webs. One component of nutrition, essential fatty acids, must be obtained by consumers through their diet. They are produced at the base of the food web by phytoplankton, bacteria, and protists, and are passed on to consumers, leaving a tracer of the food sources that support higher trophic levels. Using time series from the northern Strait of Georgia, I investigate variation within, and connections between, particulate organic matter at the food web base and zooplankton consumers across seasonal and inter-annual time scales. Shifts at the base of the food web influence the prey consumed by zooplankton—causing changes to their trophic resources and nutritional quality for predators.