SS3.19 Role of Benthic Communities in the Cycling and Balance of Nitrogen in Bays and Estuaries
Date: Friday, June 14, 2002
Time: 9:00:00 AM
Location: Oak Bay
SavageC, Dept. of Systems Ecology, Stockholm University, Stockholm, Sweden,
Elmgren, R, , Dept. of Systems Ecology, Stockholm University, Stockholm, Sweden, 
Larsson, U, , Dept. of Systems Ecology, Stockholm University, Stockholm, Sweden, 
Enhanced sewage treatment is often implemented to reduce nutrient inputs to coastal zones. A 23-year record of macrobenthos in a coastal Baltic embayment was assessed in relation to nutrient discharges and physicochemical parameters encompassing the period before discharge and following improved nitrogen (N) removal from a sewage treatment plant. Temporal variability in macrobenthic abundance and biomass conformed to general models of organic enrichment with an increase in common species during moderate sewage loading, but a reduction under excess inputs, especially in deeper basins. Redundancy analysis of whole-bay and basin-specific community changes identified sewage-derived N as the best explanatory variable with most taxa negatively correlated to sewage N. Comparison among individual basins showed that the impacts of sewage N on abundance declined with distance from the outfall. Abundance analyses suggested that full community recovery was not complete five years after initiation of tertiary sewage treatment. Finally, although sewage impacts were evident even 20 km distant from the outfall, comparisons among basins suggested that local physical features (e.g., depth) may be a crucial factor ameliorating or enhancing sewage impacts.