Water Resources Research Act Program

Details for Project ID 2016NC201B

Comparing the Impact of Organic vs. Inorganic Nitrogen Loading to the Neuse Estuary with a Mechanistic Eutrophication Model

Institute: North Carolina
Year Established: 2016 Start Date: 2016-03-01 End Date: 2017-02-28
Total Federal Funds: $9,199 Total Non-Federal Funds: $44,999

Principal Investigators: James Bowen

Project Summary: In the 1980s and 90s the Neuse River Estuary was plagued with algal blooms and fishkills. A model-based total maximum daily load (TMDL) for nitrogen (N) loading was performed in 1999 and regulations to reduce total N loading to the estuary by 30% from a 1995 baseline were implemented. Inorganic N loading to the estuary has been reduced by 15-25%, but organic N and Trent River loading has increased by approximately 15% and 30%. Algal blooms and violations of the water quality criteria for chlorophyll-a still occur throughout the estuary. In a focused one-year study we propose to update the existing two-dimensional mechanistic model of the Neuse River Estuary in order to address the following research questions: 1. Is the Neuse Estuary equally sensitive, with regard to phytoplankton biomass, to changes in organic vs. inorganic N loading? 2. Is nutrient assimilation by phytoplankton equally effective for the organic and inorganic fractions of the N loading to the estuary? 3. Is the model developed in the 1990s still able to accurately predict phytoplankton biomass given the changes in the fractionation and spatial distribution of N loading to the estuary? 4. To what extent are the changes in distribution of phytoplankton biomass, and the biomass values seen in the estuary in the 2000’s attributable to changes in changes in the N loading? 5. What role do the bottom sediments play in the cycling and phytoplankton assimilation of organic and inorganic N loading to the estuary? The project will leverage efforts by the P.I. to develop the numerical model used for the TMDL and a second model developed to predict the fate and transport of pathogenic bacteria in the Neuse Estuary. These earlier projects provide the perfect starting point for a reexamination of the linkage between nutrient loading and biomass production in the Neuse Estuary.