Coastal commentary 



Nutrients in Our Coastal Waters: 

 Too Muck off a Good Thing? 



Eating and excreting are an un- 

 avoidable part of our daily lives. 



We take these activities for 

 granted, but the resulting nutrient load- 

 ing into our rivers and estuaries is un- 

 questionable and far-reaching. As the 

 population of North Carolina contin- 

 ues to grow, so too will the damaging 

 levels of nutrients we are introducing 

 into our waters. Unfortunately, this 

 growth is outpacing the ability of regu- 

 lations to protect water quality and 

 technology to remove wastewater nu- 

 trients. 



But nutrients, in and of them- 

 selves, are not harmful. They are a vi- 

 tal component in natural coastal pro- 

 cesses. The problem is that we are 

 overloading the system, and now sci- 

 entists are investigating the environ- 

 mental repercussions. Perhaps the 

 most compelling research is under way 

 in the laboratory of JoAnn Burkholder, 

 who is examining the link between 

 high levels of phosphorus and out- 

 breaks of a newly discovered toxic 

 dinoflagellate. Burkholder is a Sea 

 Grant researcher and assistant profes- 

 sor of botany at N.C. State University. 



Food for Thought 



The food we eat and the clothes 

 we wear don't originate in the stores. 

 North Carolina and the United States 

 are checkered with agricultural and 

 animal farming operations that provide 

 the bulk of the food we serve on our 

 tables. Farmers must fertilize their 

 crops with nutrients, primarily nitro- 

 gen and phosphorus, for profitable 

 production. These nutrients are essen- 

 tial for plant growth. But the nutrients 

 applied aren't always used, depending 

 on growth rates and weather condi- 

 tions. When it rains, excess nutrients 

 may wash into nearby waters or seep 

 into the ground where they accumu- 



late, degrade or migrate into ground- 

 water. Nutrient-rich groundwater can 

 then filter into nearby surface waters. 



Wandering Waste 



Nutrients are also in animal and 

 human wastes. 



Animal waste can be washed by 

 rain into nearby surface waters from 

 livestock confinement or feed lots. 



Human waste or sewage is col- 

 lected and treated. In North Carolina, 

 most wastewater is treated by septic 

 tanks or municipal wastewater treat- 

 ment plants that do not completely re- 

 move nutrients. These nutrients then 

 meander into our coastal waters, where 

 even low levels can be damaging. Sep- 

 tic tanks, for instance, can discharge 

 nutrients into nearby coastal waters 

 through the movement of groundwater. 

 Most municipal wastewater treatment 

 plants release nutrient-laden effluent 

 directly into surface waters after treat- 

 ment. And some industries, such as 

 food processors, discharge nutrients 

 into surface waters. A few municipal 

 facilities try another tack: they treat 

 their waste less extensively and apply 

 it to large areas of land. If sited and 

 operated properly, land application can 

 minimize the release of treated effluent 

 into coastal waters. 



In Coastal Waters 



Once in our coastal waters, these 

 nutrients travel various paths. They can 

 be used by aquatic plants, remain dis- 

 solved in the water column or settle to 

 the bottom where they are stored in the 

 sediments. All of this can cause eu- 

 trophication, which is, among other 

 things, the excessive growth of algae. 

 During the day, algae produce oxygen 

 by photosynthesizing; at night, they 

 respire and consume oxygen. Decom- 

 position of the algae also consumes 

 large quantities of dissolved oxygen. 



So large algal blooms can seriously de- 

 plete coastal waters of oxygen that is 

 life-essential to aquatic organisms, es- 

 pecially fish. Eutrophication, however, 

 is not the only way excess nutrients 

 harm aquatic life. Burkholder and other 

 scientists are investigating the link be- 

 tween the frequency of toxic phyto- 

 plankton outbreaks and the increased 

 level of nutrients in our coastal waters. 

 Toxic algae sometimes rob the water of 

 oxygen, but they can affect aquatic life 

 and humans in other ways, even caus- 

 ing death. 



Progress Against Pollution 



North Carolina has made signifi- 

 cant reductions in point source dis- 

 charges of nutrients from wastewater 

 treatment plants and industries since 

 1975, when it was delegated the au- 

 thority of the National Pollution Dis- 

 charge Elimination System program by 

 the U.S. Environmental Protection 

 Agency. As a result, the state deter- 

 mines when, how much and where 

 wastewater can be discharged, using 

 federal standards. 



In addition, the state's 1988 ban on 

 phosphate detergents has significantly 

 reduced phosphorus inputs. Today, our 

 largest contributor of nutrients is agri- 

 culture, which is considered a nonpoint 

 source of pollution. The EPA and N.C. 

 Department of Environment, Health 

 and Natural Resources are moving to- 

 ward new regulatory strategies that will 

 reduce nonpoint source nutrients in our 

 surface waters. 



But still unmeasured is the contri- 

 bution of nitrogen from air pollution in 

 North Carolina's coastal waters. Nitro- 

 gen from automobiles or smokestacks 

 can land directly on the water or accu- 

 mulate in rainfall. 



Barbara Doll, Sea Grant 

 Coastal Water Quality Specialist 



24 SEPTEMBER/OCTOBER 1993 



