Comparative ecosystem trophic structure of three U.S. mid-Atlantic estuaries

Abstract

Quantitative networks of trophic exchanges offer the potential to compare food webs from neighboring ecosystems in order to ascertain whether large differences and similarities exist in trophic structure and function. Network analysis was invoked to compare the exchanges of carbon in 3 mid-Atlantic estuaries on the eastern U.S. coast: the Narragansett, Delaware, and Chesapeake Bays. Narragansett Bay exhibited the highest average annual rate of net primary production, followed by Delaware and Chesapeake Bays. Taken in combination, the analyses of cycling structures (magnitude of flows, average carbon cycle lengths), organization of carbon flows, system production:biomass ratios, and harvest rates 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, cycling structure, and food web connectivity was employed. The results indicated that Delaware Bay is currently less impacted and has potentially more ability to mitigate perturbations to its food web than does Chesapeake Bay. Overall, network analysis proved to be a suitable methodology for making inter-estuarine ecosystem comparisons, and for providing useful insights to natural resource managers in the assessment of estuarine trophic structure and status.