REU: Mechanisms Controlling the Production and Fate of Insect Detritivores in the Profundal of Lakes

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Much of the organic matter produced in lakes sinks to profundal sediments where it supports a community of benthic detritivores, often dominated by larvae of the Chironomidae. These insects (midges) are an important trophic link between phytoplankton and fish. It is generally thought that lakes more productive of phytoplankton will have higher secondary production by this detritivore community, and ultimately by fish. We do not know how closely these ecosystem components are linked, nor do we understand possible trophic and life history mechanisms for such coupling. This research asks whether production by profundal chironomids reflects the food supply to this community, or whether population densities are often too low to fully utilize available resources. Pilot experiments will develop techniques for manipulating food supply and larval recruitment to the profundal benthos to test hypotheses regarding factors that may limit profundal insect production. A model of secondary production by a dominant profundal species will also quantify the loss of production to fish through predation on ascending pupae. This work will clarify the role of the profundal benthos in the trophic linkage between primary production and fish.