A multi-year (1990-1993) field survey and in situ bioassay study was undertaken to examine trophic and biogeochemical impacts of nutrient loading events at 3 representative oligohaline and mesohaline locations in the Neuse River Estuary North Carolina. Additional data were evaluated from an earlier study (1987-1990) at a mesohaline location. Previous studies showed the estuary as being nitrogen-limited throughout much of th year. In addition there is evidence and concern that recent increases in nitrogen loading have led to spatial and temporal expansion of phytoplankton blooms, indicating accelerating eutrophication. Accordingly, we examined the roles of significant nitrogen (N) inputs on the eutrophication process.