The seasonal dynamics of the Chesapeake Bay ecosystem

The full site of carbon exchanges among the 36 most important components of the Chesapeake Bay mesohaline ecosystem is estimated to examine the seasonal trends in energy flow and the trophic dynamics of the ecosystem. The networks provide information on the rates of energy transfer between the trophic components in a system wherein autochthonous production is dominated by phytoplankton production. The summer grazing of primary producers by zooplankton is greatly reduced due to top-down control of zooplankton by ctenophores and sea nettles. Some of the ungrazed phytoplankton is left to fuel the activities of the pelagic microbial community, and the remainder falls to the bottom where it augments the deposit-feeding assemblage. There is a dominant seasonal cycle in the activities of all subcommunities, greatest in summer, least in the cold season. The complicated trophic network can be mapped into an 8-level trophic chain. Detritivory is c10 times greater than herbivorous grazing in the Chesapeake system; 70% of detritus results from internal recycle. The number of cycles present in the network is surprisingly few, despite the fact that a relatively large and seemingly constant amount (23.2%) of total system activity is devoted to recycling. This combination of factors possibly indicates a stressed ecosystem. Study of the rate-limiting links in the seasonal networks of recycling of material within the plankton reconfirms the shift of predator control from crustaceous zooplankton in spring-time to the sea nettle Chrysaora quinquecirrha during summer months. -from Authors