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HARBOR UPDATE. Transfer of Nut Island flows, and changes in the water quality of Boston Harbor David Taylor. NITROGEN LOADINGS TO BOSTON HARBOR.
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HARBOR UPDATE Transfer of Nut Island flows, and changes in the water quality of Boston Harbor David Taylor
NITROGEN LOADINGS TO BOSTON HARBOR • Boston Harbor receives loadings of total nitrogen (TN) from terrestrial plus atmospheric sources of 6.6 x 105 kmol y-1 (Kelly 1998). • This is among the highest reported for any bay or estuary in the USA (Kelly 1991, Nixon et al. 1996). • >90% of these inputs occur from wastewater (Alber and Chan 1994).
SYMPTOMS OF EUTROPHICATION • Elevated nutrient concentrations (Kelly 1998) and phytoplankton biomass (HydroQual 1994) • Almost total demise of seagrass beds, and heavy epiphytization of remaining beds (Colaruso, EPA) • Low dissolved oxygen concentrations in Inner Harbor (MWRA unpubl. data) • Supports benthic invertebrate communities typical of moderately degraded environments (Blake et al. 1998).
CONCLUSIONS • Changes in water quality have been observed in Boston Harbor since transfer of Nut Island flows. • The South Harbor has shown decreased concentrations of DIN, increased water clarity, and variable responses of biomass of phytoplankton. • The North Harbor has shown increased DIN concentrations, a small increase in clarity at the outfalls, and no change in phytoplankton biomass. • The phytoplankton responses to increased nitrogen loadings appear to have been manifested in west Mass Bay.