Monday, 4:00 PM in BR D (RICC)
(subject to change)
Estimates of external nutrient loading to shallow coastal bays are in the same range as those for deeper estuaries, even though their watersheds are significantly smaller and most lack riverine inputs. Coastal bays differ from deep estuaries in two fundamental ways: 1) the photic zone extends to most of the seafloor, and the benthos typically dominates primary production, and 2) high rates of metabolism of benthic primary producers mediate nutrient cycling processes and result in strong benthic-pelagic coupling. We determined nitrogen assimilation and turnover of primary producers in West Falmouth Harbor, a shallow coastal ecosystem in Massachusetts, which is influenced by groundwater enriched by a nearby sewage treatment facility. We compared sites that varied in nutrient loading and related nitrogen assimilation to external nutrient inputs. Combined nutrient assimilation by primary producers (microalgae, macroalgae and rooted macrophytes) was similar to, or in excess of, external nutrients, suggesting that most nutrients entering these systems pass through the primary producer communities. Although the biomass and production rates vary among primary producer groups, the magnitude of nutrient assimilation is often similar, indicating that the turnover time and fate of nutrients bound in plant tissue is important in the eutrophication response of these systems.
