The Effects of Nutrient Pollution on the Neuse River Estuary

THE EFFECTS OF NUTRIENT POLLUTION ON THE NEUSE RIVER ESTUARY

Valerie Winkelmann

When most people think of pollution in a body of water, they think of an oil slick from an oil spill or some type of “chemical” being released from a factory. How can nutrients be a pollutant? Naturally, eutrophication, or the enrichment of a water mass with organic and inorganic plant nutrients, is beneficial because it increases productivity of the body of water (Boney 1975). However, with increased anthropological inputs, nutrient loading has become a source of pollution. Accelerated enrichment by artificial means produces explosions of phytoplankton populations (Boney 1975). Increases in phytoplankton population, or algal blooms can have serious effects on the ecosystem of estuaries.

In the Neuse River Estuary, “enhanced phytoplankton production and algal blooms, symptoms of eutrophication, are frequently caused by elevated nutrient loading, usually as nitrogen” (Mallin et al. 1993). After a point, the algal bloom will die off and begin to decompose. Bacterial decomposition is an oxygen sink because the bacteria take in oxygen from the water as they respire. Decreased dissolved oxygen can cause fish, shellfish, and crabs to die; thus, harming the local fisheries. Phytoplankton are important because they are the base of the food chain. Changes in abundance of phytoplankton or distributions of phytoplankton species can affect the entire trophic system. Also, nutrient loading can lead to toxic blooms such as Pfiesteria. The toxic dinoflagellate Pfiesteria piscicida causes possible fish mortality and reported health implications (Pinckney et al. 2000).

Nitrogen in the Neuse River Estuary is derived primarily from anthropogenic sources (Mallin et al. 1993). Urban sources of nutrients come from runoff due to increased impervious coverage and municipal wastewater treatment plants. Sewage treatment plants have total annual loadings of 2.1 x 10^6 kg of nitrogen with a 17% increase in human population over the past decade. Industrial inputs include 441 point dischargers with total annual loadings of 2.1 x 10^6 kg of nitrogen. Agricultural sources include fertilizer and concentrated animal operations. Manure produced by swine and poultry, contributed 4.1 x 10^7 kg of nitrogen in 1998 (Glasgow and Burkholder 2000). Other sources on nitrogen include release from the sediments (Rizzo et al. 1992) and atmospheric deposition (Rudek et al. 1991).

State regulations require a 30% reduction in nitrogen loading by 2003. In urban areas nitrogen loading can be reduced by reducing impervious coverage, create retention ponds, and establishing riparian buffers. All of these practices would decrease runoff in the Neuse River watershed. Industrial point source polluters should have strict regulations and be monitored strenuously. For agricultural sources of nutrient pollution there are several best management practices (BMP’s) that could be implemented. The NC Cooperative Extension has published the following as BMP’s: riparian buffers, nutrient management, controlled drainage, and a conservation tillage system.

All of these practices would be effective means of reducing nitrogen loading in the Neuse River Estuary. None of them are extremely expensive, but no one is going to want to spend money on these systems if it is not required. I feel we have the means to control the amount of nutrients coming into the system; thus maintaining the estuary in a productive state that is beneficial instead of harmful. Before this can happen, there needs to be widespread public demand for normal nutrient levels in the Neuse River. Unfortunately, this problem probably won’t get the regulatory attention it really needs until water quality is extremely diminished.

Works Cited

Boney, A. D. Phytoplankton. New York: Crane, Russak and Company, INC., 1975.

Glasgow, H. B. and J. M. Burkholder. “Water Quality Trends and Management Implications from a Five-year Study if a Eutrophic Estuary.” Ecological Applications 10.4 (2000): 1024-1046.

Mallin, M. A., H. W. Paerl, J. Rudek, and P. W. Bates. “Regulation of Estuarine Primary Production by Watershed Rainfall and River Flow.” Marine Ecology Progress Series 93 (1993): 199-203.

North Carolina Cooperative Extension Service. Cost and Benefits of Best Management Practices to Control Nitrogen in the Lower Coastal Plain.

Pinckney, J. L., H. W. Paerl, E. Haugen, and P. A. Tester. “Responses of Phytoplankton and Pfiesteria-like Dinoflagellate Zoospores to Nutrient Enrichment in the Neuse River Estuary, North Carolina, USA.” Marine Ecology Progress Series 192 (2000): 65-78.

Rizzo, W. M., G. J. Lackey, and R. R. Christian. “Significance of Euphotic, Subtidal Sediments to Oxygen and Nutrient Cycling in a Temperate Estuary.” Marine Ecology Progress Series 86.1 (1992): 51-61.

Rudek, J., J. W. Paerl, M. A. Mallin, and P. W. Bates. “Seasonal and Hydrological Control of Phytoplankton Nutrient Limitation in the Lower Neuse River Estuary, North Carolina.” Marine Ecology Progress Series 75.2-3 (1991): 133-142.