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Control of Copepod Populations by Predators:
Larval Ctenophores
The objective of the research is to determine predation rates on
Acartia tonsa nauplii and copepodites due to tentaculate larval
Mnemiopsis ctenophores. These predators may be extremely important in controlling copepod population densities. This research examines predation not yet addressed in my ongoing research on the impacts of medusae and adult ctenophores on copepod populations. This research is a complete examination of the major pelagic predators on Acartia copepods in the mesohaline region of Chesapeake Bay.
This research is a critical next step towards understanding the importance of top-down control of copepod populations in Chesapeake Bay. Copepods are the main food of many fish species in the Bay, and are major grazers of phytoplankton. Factors, such as predation, that may limit copepod population sizes therefore also may limit fish populations. Predation also may indirectly increase phytoplankton and consequently reduce water quality. Fishery resources and water quality are primary concerns in Chesapeake Bay. This new and ongoing research by myself and others will allow us to evaluate the relative importance of the major pelagic predators of copepods in Chesapeake Bay - gelatinous zooplankton and fish. As well as adding larval ctenophores to this study of predation, the new research is essential to evaluate the adequacy of previous net sampling for small ctenophores. This research will be useful to biologists and managers concerned with the resources and water quality in Chesapeake Bay and elsewhere. It will enable scientists to compare top-down processes in an estuary with those in comparatively well-studied lake ecosystems. Predation impact on copepod populations is crucial to understanding the complex trophic dynamics in the Bay.
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Jennifer Purcell
Horn Point Laboratory
University of Maryland Center for Environmental Science
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