Hypoxia as a Mediator of Food Web Interactions and Energy Flow in Reservoir Ecosystems
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Date
2012-03
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The Ohio State University
Abstract
Hypoxia has emerged as a prominent research and management issue in freshwater and marine ecosystems worldwide, primarily owing to cultural eutrophication. Our understanding of hypoxia’s impacts on aquatic food webs, particularly pelagic ones, is limited, however. Herein, we explore how hypoxia can influence reservoir food web interactions involving age-0 fishes (e.g., gizzard shad Dorosoma cepedianum; crappies Pomoxis spp.; bluegill sunfish Lepomis macrochirus), the phantom midge (Chaoborus punctipennis), and their shared mesozooplankton prey. From sampling with midwater trawling and zooplankton pumping during day and night in Hoover Reservoir, Ohio before, during, and after the hypoxic period in 2011, we learned that hypoxia-driven disruption of the diel vertical migration (DVM) behavior in both planktivore types caused high overlap with mesozooplankton prey in the oxygenated epilimnion during the hypoxia period. Further, Chaoborus began to feed during the day (not just the night) in the presence of hypoxia and its consumption of mesozooplankton taxa of importance to fish increased. Using this information, in conjunction with diet overlap and prey size- and taxa-selectivity data for Chaoborus and fish, we discuss the potential for hypoxia to regulate the foraging and growth environment for age-0 reservoir fishes via altered energy flow through the food web.
Description
Mayers Summer Research Scholarship
Keywords
anoxia, reservoirs, predation, planktivory, dead zone