1998 Year of the Ocean Perspectives on Marine Environmental Quality 



Water Quality in Marine Ecosystems 



To understand the current status of water quality in marine environments, it is necessary 

 to consider nutrients levels, along with the extent of contamination by pathogens, chemicals, oil, 

 and debris/litter. 



Nutrients 



Nutrients have an ambiguous position in the assessment of water quality — ^they are 

 necessary to support healthy marine ecosystems, but in excess, they can lead to severe oxygen 

 depletion. Excess nutrients also stimulate the growth of dino flagellates and nuisance algae, such 

 as blue-greens which are often toxic to estuarine and marine animals. This stimulation in growth 

 know as blooms, can have such effects as causing fish kills or manatee deaths, and in some 

 instances may threaten human health. Since the end of World War II, increases in human 

 population density, fertilizer use, animal husbandry, and changes in land use, have contributed to 

 increased nutrient inputs from runoff that range in magnitude from two- to ten-fold. It has been 

 estimated that 40 percent of estuarine and coastal waters are not "fishable or swimmable," 

 primarily because of nutrients and bacteria from urban and agricultural runoff and municipal 

 wastewater discharges (U.S. EPA, 1995a). Recent studies have shown air deposition of nitrogen 

 is also a significant contributor to nutrient over-enrichment of marine waters. For example, 21 

 percent of nitrogen loadings to the Chesapeake Bay are from air deposition (Valigura, 1996). 



Pathogen Contamination 



Viruses, bacteria, and protozoa can cause diseases in plants, humans, and other animals. 

 In excess, they contribute to closures of shellfish beds and swimming areas, fish kills, and 

 seafood consumption warnings. The good news is that "approved" shellfish harvest waters are at 

 an all time high. Of the 25 million shellfishing acres classified in 1995, about 59 percent are 

 "approved" for shellfishing, and restrictions on shellfishing waters are at their lowest levels since 

 1980. There has been a significant decrease in shellfishing acreage that has harvest limitations 

 due to pollution from industry, wastewater treatment plants, and direct discharges; however, 

 there has been an increase in the acreage that is "harvest limited" as a result of boating, marinas, 

 urban runoff, and agricultural runoff (NO AA, 1997). Overall, the condition of shellfish harvest 

 waters in the United States is improving. 



During 1996, there were at least 2,596 individual closings and advisories for ocean, bay, 

 and Great Lakes swimming beaches due to bacterial contamination. Over 80 percent of the beach 

 closings and advisories in 1996 were based on monitoring that detected bacteria levels exceeding 

 beach water quality standards.^' Decreases in hurricane activity in Florida and decreases in the 

 number of heavy storms in California (NRDC, 1997) resulted in fewer combined sewer overflow 

 events and reduced the number of beach closings in 1996. The number of beach closings due to 



21 For, example, beaches can be closed to swimming wlien there is a rislc of catching waterbome diseases from raw sewage 

 contamination. 



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