Estuaries of the northeastern United States: Habitat and land use signatures

Geographic signatures are physical, chemical, biotic, and human-induced cha racteristics or processes that help define similar or unique features of es tuaries along latitudinal or geographic gradients. Geomorphologically, estu aries of the northeastern U.S., from the Hudson River estuary and northward along the Gulf of Maine shoreline, are highly diverse because of a complex bedrock geology and glacial history. Back-barrier estuaries and lagoons oc cur within the northeast region, but the domiant type is the drowned-river valley, often with rocky shores. Tidal range and mean depth of northeast es tuaries are generally greater when compared to estuaries of the more southe rn U.S. Atlantic coast and Gulf of Mexico. Because of small estuarine drain age basins, low riverine hows, a bedrock substrate, and dense forest cover, sediment loads in northeast estuaries are generally quite low and water cl arity is high. Tidal marshes, seagrass meadows, intertidal mudflats, and ro cky shores represent major habitat types that fringe northeast estuaries, s upporting commercially-important fauna, forage nekton and benthos, and coas tal bird communities, while also serving as links between deeper estuarine waters and habitats through detritus-based pathways. Regarding land use and water quality trends, portions of the northeast have a history of over a c entury of intense urbanization as reflected in increased total nitrogen and total phosphorus loadings to estuaries, with wastewater treatment faciliti es and atmospheric deposition being major sources. Agricultural inputs are relatively minor throughout the northeast with relative importance increasi ng for coastal plain estuaries. Identifying geographic signatures provides an objective means for comparing the structure, function, and processes of estuaries along latitudinal gradients.