US-GLOBEC: Phytoplankton and Protozoa in the Diets of Copepods and Larval Cod on Georges Bank

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9313678 Gifford This project represents one component of a multidisciplinary, multi-investigator program under the aegis of the U.S.-GLOBEC Northwest Atlantic initiative. The overall program, described in the Prologue to this proposal, proposes to study the life histories and vital physiological rates leading to recruitment of cod, haddock, and their food resources on Georges Bank. Specifically, this project seeks to describe quantitatively and qualitatively the nano- and micro- plankton prey fields on Georges Bank and to measure consumption of nano- and microplankton organisms (i.e. plant and animal prey 2-200 um in size) by early life history stages of Atlantic cod, Gadus morhua, and by all copepodid life history stages of one of its major prey species, the calanoid copepod, Calanus finmarchicus, under various conditions of water column mixing and stratification on Georges Bank. Ingestion rates of consumers will be measured directly in shipboard experiments using natural prey assemblages. The proximate influence of omnivorous feeding on the consumers will be interpreted in the context of the in situ prey field and physical regime (mixing versus stratification). Ultimately, the influence of plant versus animal prey in consumer diet will be addressed collaboratively in the context of measurements made by other investigators of consumer distribution, condition, life history parameters and production. ***