Chesapeake Bay nutrient and plankton dynamics. 2. Sources and sinks of nitrite

The transformations of inorganic nitrogenous nutrients that can lead to the frequently observed high levels of nitrite in the Chesapeake Bay and York River were investigated by a combination of 15N tracer techniques and assays of the concentrations of chemical constituents (NH4+, NO2-, NO3-, O2, N2O, and CH4). The distributions of N2O, NO2-, and CH4 in the York River suggest that the primary source of N2O and NO2-, both produced during nitrification, was in the water rather than in the sediments. Our 15N data indicate that oxidized N can be formed in the water of the bay when physical events cause the mixing of NH4+-rich bottom water with more oxygenated surface layers. We also found that NO3- was reduced to NH4+ at unexpectedly rapid rates in well oxygenated surface waters. The magnitude and duration of high concentrations of N2O and NO2- in these estuarine waters during mixing events might be expected to increase if anthropogenic loading of nutrients causes anoxic conditions in the bay to become more widespread