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Does Low Dissolved Oxygen Favor Dominance of Gelatinous Zooplankton in Chesapeake Bay?
Heavy nutrient loading, primarily from land runoff, sewage plant discharges and airborne deposition continues to be a major cause of oxygen depletion in the Chesapeake Bay and estuaries throughout the world. An indirect consequence of this environmental change may be to favor gelatinous zooplankton–the Bay's stinging sea nettles and small ctenophores–which outcompete young fish and other organisms that are more physically stressed by such conditions. Gelatinous species are voracious feeders. During the summer, for example, sea nettles can consume more than 90 percent of copepod standing stocks a day; nettles and ctenophores have been observed to consume nearly 55 percent of Bay anchovy egg production. Both sea nettles and the abundant ctenophore
Mnemiopsis leidyi are more tolerant of low dissolved oxygen than are Bay fishes. While there is a good scientific understanding of the effects of low oxygen levels on organisms that gelatinous species prey upon, there have been no direct measures of the effects that low oxygen has on growth and reproduction of the gelatinous species themselves. This information is essential if scientists are to discern how the impact of oxygen depletion propagates through estuarine food webs. In this project, Denise Breitburg and Jennifer Purcell will conduct extensive experiments to explore these relationships with the goal of predicting outcomes under different environmental conditions. Their findings will have direct value in enhancing predictive water quality models, which decision makers use in formulating policies for restoration of the Chesapeake Bay.
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Denise Breitburg
The Academy of Natural Sciences
Estuarine Research Center
Jennifer E. Purcell
Horn Point Laboratory
University of Maryland Center for Environmental Science
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