Rivers and estuaries are sites of intensive microbial degradation of organic matter. In the Hudson River we have documented spatial variation in bacterial production (Fig. 1) based on samples taken at 5 km. intervals from the Tappan Zee Bridge (river kilometer 42) to Albany (river km 232). Highest production is consistently observed in the section above river km 200. Production declines downriver and is relatively constant below river km 125. The Albany reach of the estuary (above river km. 200) represents a zone of elevated carbon degradation and intense microbial activity.

The Albany reach receives discharges from sewage treatment plants and, during wet weather, combined sewer overflows and storm drains (see photo below). Standard sewage treatment reduces organic matter in effluents but not nutrients such as phosphorus. Elevated activity may be related to increased inputs of easily degraded organic matter and/or to enhanced inputs of inorganic nutrients (nitrogen and phosphorus). High nutrient concentrations in the Albany reach may provide conditions more favorable to bacteria promoting organic matter degradation within the river. Current research is testing this possibility.