Even before European settlement, nutrient loading per area of the estuary was probably high in the Hudson River compared to most estuaries, because of the high ratio of watershed area to estuary area (Table 10.1). At the scale of large regions, the nitrogen flux into the North Atlantic Ocean per area of watershed in the temperate zone is a linear function of the net anthropogenic inputs of nitrogen per area to the region. The zero intercept of this relationship, corresponding to no human influence, gives an estimate of the riverine nitrogen export from the pristine landscape of approximately 100 kg N km-2 y-1 (Howarth et al., 1996b; NRC, 2000). This relationship holds well at a smaller scale, as seen for sixteen major watersheds in the northeastern United States, including the Mohawk River basin and the upper Hudson River basin
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