Interactions of Physics and Biology: Gelatinous Predators in Chesapeake Bay

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Purcell 9633607 This research will interface with the ongoing 5-yr LMER II program (TIES) in Chesapeake Bay, which will provide logistic and analytical support and data on hydrography, mesozooplankton, and ichthyoplankton. A bay-wide data set will be collected on the distribution of gelatinous predators (medusae and ctenophores), as they are related to large-scale hydrographic features in the water column. The features of particular focus will be the seasonal pycnocline, fronts, the hydraulic control point, and biological patches. Regions of the bay for intensive mapping, and process-oriented studies include the polyhaline southern bay and the mesohaline mid-bay. In process-oriented studies, feeding and fecundity will be measured to determine if trophic interactions increase at hydrographic features. TIES will continuously measure mesozooplankton abundances and temperature, salinity, chlorophyll, and dissolved oxygen. Depth-discrete samples of gelatinous predators will be made using an opening closing net system. Biovolumes, numbers, and sizes of the live gelatinous organisms will be determined on board ship. Small and delicate specimens (larval ctenophores and hydromedusae) will be quantified from additional vertical plankton hauls. Individual specimens will be collected and (1) preserved immediately for gut content analysis, and (2) incubated overnight for egg production. Data analysis will emphasize 3-dimensional mapping and correlations of hydrographic data with population data on regional, seasonal, and interannual bases, as well as comparisons of the trophic and reproductive data relative to hydrographic features. Gelatinous predators are important components of the pelagic food web in Chesapeake Bay. Aggregations of jellyfish occur because of interactions of their behaviors with the physical characteristics of the water column. Chesapeake Bay is physically complex, with many possible aggregating features. Population data exist for only three gelatinous species in the bay, but 30 species have been reported. This research will provide critical studies on how physics and biology interact to cause intensification of trophic interactions at fronts and other physical features. ***