| Sediment organic matter (OM), sediment oxygen demand (SOD), denitrification, and sediment nutrient (NH4+, NO3 - PO4-3) flux were observed across a salinity gradient within the Neuse River Estuary (NRE) over a three-year period (1998--2000) and examined for spatial and temporal patterns, and for correlations among each other. Spatial differences in OM and NH4 + flux were observed along the salinity gradient, with maximum concentration and flux occurring mid-estuary. This pattern was not reflected in the SOD, which remained constant. NH4+ flux was positively correlated with OM and SOD. NO3- and PO4-3 fluxes showed no spatial variation, were small, and unrelated to OM.; Decreases in SOD and nutrient fluxes due to benthic microalgal communities (BMC) were observed in shallow NRE environments. Potential increased habitat for BMC was investigated for an enacted management strategy designed to decrease nitrogen (N) loads to the NRE by 30%. Results indicate that the compensation depth could deepen by 13 cm due to the mandated reductions, leading to a 20% increase in euphotic sediments. BMC colonization of the newly euphotic regions could lead to decreased SOD and N release.; Sediment Chlorophyll a varied inter-annually and seasonally in response to changes in riverine discharge, phytoplankton primary productivity and subsequent sediment OM loading. SOD and nutrient flux varied little over inter-annual timescales. No seasonalty was observed for SOD, NO3- flux and PO4-3 flux, but NH 4+ flux was significantly increased in summer and fall.; Denitrification rates remained stable across the salinity gradient, but did vary seasonally, with highest rates occurring in winter. SOD and NH 4+ flux were positively correlated with denitrification at M-38, indicating coupled nitrification/denitrification activity. NO 3- addition experiments showed that denitrification activity could be stimulated. The stimulatory effect differed across the salinity gradient, suggesting the appearance of other limiting factors.; A constructed N-budget demonstrated that most N entering the NRE was from external sources, and organic in nature. Internal N sources were only capable of supporting 7% of the annual water column N-demand. N removal via denitrification accounted for 12% of the total annual N-load and 22% of the annual dissolved inorganic N-load. |
