Trophic Dynamics Key species and communities in the Chesapeake Bay have received a great deal of attention from MDSG because of the pivotal ecological positions they occupy in the Bay's food web, and the commercial and recreational importance of harvestable forms. This focus on trophic dynamics is central to our mission and addresses the interconnections of species within the Bay ecosystem, as shown in relevant examples from the MDSG sponsored research that includes projects spanning bacteria to gelatinous zooplankton to fish. It is clear that bacteria are instrumental in both nutrient regeneration and oxygen consumption in the Bay ecosystem. This study began to differentiate groups of microbes and to provide a more realistic view of how microbial communities function in Chesapeake Bay. The negative impact of jellyfish, or sea nettles, of the genus Chrysaora on recreational activities is well known as these summer occupants of Bay waters make swimming uncomfortable or impossible for several months.
Larval fish tend to enter areas of low dissolved oxygen to escape predation from larger fish.
Gelatinous zooplankton, however, are not affected by hypoxia to the same extent as other predators, and can prey effectively on the juvenile fish weakened by low dissolved oxygen concentrations. Results showed that copepod abundance was not constrained by predation from gelatinous zooplankton or by food supply. The potential top-down role of gelatinous zooplankton on copepods is complicated by the occurrence of large populations of ctenophores of the genus Mnemiopsis , an important prey item of Chrysaora that at the same time is a voracious consumer of herbivorous copepods. Regional meteorological conditions also influence the trophic dynamics of the gelatinous zooplankton as years of strong freshwater flow suppress or delay Chrysaora , while permitting an expansion of the Mnemiopsis population. These interactions accentuate the complex trophic interactions in the plankton of this ecosystem.