COMPARATIVE ECOSYSTEM TROPHIC STRUCTURE OF 3 US MID-ATLANTIC ESTUARIES

Quantitative networks of trophic exchanges offer the potential to comp are food webs from neighboring ecosystems in order to ascertain whethe r large differences and similarities exist in trophic structure and fu nction. Network analysis was invoked to compare the exchanges of carbo n in 3 mid-Atlantic estuaries on the eastern U.S. coast: the Narragans ett, Delaware, and Chesapeake Bays. Narragansett Bay exhibited the hig hest average annual rate of net primary production, followed by Delawa re and Chesapeake Bays. Taken in combination, the analyses of cycling structures (magnitude of flows, average carbon cycle lengths), organiz ation of carbon flows, system production:biomass ratios, and harvest r ates all indicated that the Delaware and Chesapeake Bay ecosystems are more stressed than that of Narragansett Bay. To differentiate between the former two, a combination of measures of system efficiency, cycli ng structure, and food web connectivity was employed. The results indi cated that Delaware Bay is currently less impacted and has potentially more ability to mitigate perturbations to its food web than does Ches apeake Bay. Overall, network analysis proved to be a suitable methodol ogy for making inter-estuarine ecosystem comparisons, and for providin g useful insights to natural resource managers in the assessment of es tuarine trophic structure and status.