RESUMEN
This paper documents the changes that followed large nutrient (N and P) and organic matter input reductions to a major metropolitan marine bay, Boston Harbor (USA). Before input reduction, its N and P inputs fell in the upper range of the < 1-> 300 gN m-2 year-1 and < 0.1-> 40 gP m-2 year-1 for coastal systems. Elevated nutrient and organic matter inputs are recognized causes of coastal eutrophication. Treatment upgrades and then diversion of its wastewater discharges offshore, lowered its N, P, and organic C inputs by 80-90%. The input decreases lowered its trophic status from hypereutrophic to eutrophic-mesotrophic. With the reversal of hypereutrophication, pelagic production and phytoplankton biomass decreased, and the nitrogen limitation relative to phosphorus limitation increased. Benthic metabolism and dissolved inorganic N fluxes decreased, and benthic-pelagic coupling was altered. Bottom-water dissolved oxygen, already at healthy levels, increased, and seagrass expanded. Coastal management requires that the changes, following the nutrient and organic matter input reductions implemented to address eutrophication, be understood. Boston Harbor's recovery, because its water column was vertically well mixed and marine, was more pronounced than in many other systems.
Asunto(s)
Eutrofización , Aguas Residuales , Boston , Monitoreo del Ambiente , Nitrógeno , Fósforo , FitoplanctonRESUMEN
Chemical carcinogen biomarkers can validate public investment in environmental remediation. A major factor driving the clean-up of Boston Harbor, MA, USA, induced by the federal Clean Water Act legislation of 1972, was the high prevalence of petroleum and halogenated aromatic hydrocarbon contaminant-associated liver neoplasia in winter flounder Pseudopleuronectes americanus in the harbor in the 1980s. In the present study, we examined the spatial and temporal relationships between the suspended solids and contaminants in the municipal sewage discharge, and liver neoplasia and histopathology in flounder, from 1987 to 2017. Toxics source reduction, sewage treatment, and sludge removal in the 1990s and outfall relocation offshore in 2000 enabled a decreasing prevalence of persistent toxic chemicals in flounder, effluent, and sediment, and consequent disappearance of liver neoplasia and reduction of neoplasm-associated, hydropically vacuolated biliary epithelial cells to background levels. This supports long-term investment in elimination and treatment of anthropogenic waste streams and the value of federal regulatory mandates to maintain and improve regional environmental quality.
Asunto(s)
Lenguado , Neoplasias Hepáticas/veterinaria , Contaminantes Químicos del Agua , Animales , Boston , Hígado , Aguas del AlcantarilladoRESUMEN
The Massachusetts Water Resources Authority (MWRA) conducts monitoring to address concerns related to the 2000 diversion of secondarily treated effluent discharge into Massachusetts Bay. Baseline data (1992-2000) showed multiple regions defined by physical and chemical composition. Near the Massachusetts Bay outfall, there is a series of heterogeneous sediments in relatively close proximity to the primary historic source of contaminants (Boston Harbor). Farfield sediments exhibited greater compositional definition from one another, which was attributed to the greater spatial separation of the sampling locations. Factors that influence contaminant variability include local and distributed sources, and are primarily related to gradients in depositional environments. Post-diversion sediment data suggest that 4 years of treated effluent discharge has not increased contaminant concentrations to the bay system. However, abundance of the sewage tracer, Clostridium perfringens, has increased variably in sediments located within 2 km of the outfall, providing a distinct effluent signal near the outfall.