Three decades of monitoring in Chesapeake Bay and tributary rivers has allowed for an examination of the spatial and temporal patterns of water quality change in response to watershed restoration activities. This review of past monitoring data has revealed clear signs of successful water quality remediation in some Chesapeake regions. Upgrades to waste water treatment plants (WWTP) have led to measurable reductions in nutrient concentrations and algal biomass, with associated recoveries of submerged aquatic vegetation and reductions in sediment and nutrient levels. Point-source related improvements were observed in waters local to the WWTP facility, which are generally in oligohaline and tidal freshwater regions of tributaries. Reductions in atmospheric deposition of nitrogen within the Bay watershed has resulted inmarked reductions in nitrogen inputs from the Susquehanna and Potomac Rivers, and these reductions in watershed input have resulted in lower concentrations within the estuary. Coastal plain watersheds with high agricultural intensity continue to yield high amounts of nutrients, and water quality has not improved in the receiving waters of many of these tributaries. Signs of eutrophication remediation are clearest where nutrient load reductions are large and local. In more seaward estuarine reaches, recovery from eutrophication appears to be season- and regionspecific, where the late growing season period in high-salinity waters, which is most vulnerable to nutrient limitation and oxygen replenishment, appear to have recovered first. These findings suggest a refinement of our existing conceptual models of the eutrophication process in Chesapeake Bay, where time of year and proximity to nutrient sources are important to understanding spatial and temporal variation in recovery.

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