Oceans and Estuaries - The 2000 National Waterquality Inventory

Oceans

In its 2000 National Water Quality Inventory (2002), the EPA reported that fourteen of the twenty-seven coastal states and territories had rated the water quality of some of their coastal waters. The states had assessed 14% of the 22,618 miles of national coastline excluding Alaska, or 5.5% (3,221 miles) of ocean shoreline (including Alaska's 36,000 miles of coastline). Of the 14% of ocean waters assessed, 79% fully supported their designated uses, 14% were impaired, and 7% were supporting uses but threatened. Designated uses are the beneficial water uses assigned to each water body by a state as part of its water quality standards. Examples of designated uses are fishing and drinking water supply.

In this 2000 EPA report, bacteria (pathogens) were identified by ten states as the leading contaminants of ocean shoreline waters, followed by oxygen-depleting substances and turbidity (cloudiness). (See Figure 6.5.) Bacteria provide evidence of possible fecal contamination that may cause illness. States use bacterial indicators to determine if oceans are safe for swimming or secondary contact recreation, such as water skiing. Figure 1.7 in Chapter 1 shows the pathways of bacteria to surface waters. The most common sources of bacteria are urban runoff, inadequately treated human sewage, and runoff from pastures and feedlots, all of which were identified FIGURE 6.5
Leading pollutants in impaired ocean shoreline waters, 2000
SOURCE: "Figure 4-11. Leading Pollutants in Impaired Ocean Shoreline Waters," in 2000 National Water Quality Inventory, U.S. Environmental Protection Agency, August 2002 by ten states as leading sources of ocean shoreline impairment (see Figure 6.6).

Turbidity is a measure of the relative clarity of water. Turbidity is caused by suspended matter or other impurities that make the water look cloudy. These impurities may include clay, silt, finely divided organic and inorganic matter, plankton, and other microscopic organisms. It interferes with the transmission of light to underwater grasses and other plant life in need of this light. If the transmission of light is reduced due to heavy silt in the water this can smother bottom-dwelling organisms such as oysters. Turbidity was responsible for more than 10% of the impaired ocean shoreline miles reported to the EPA in 2000. Three of the leading sources of ocean impairment are also contributors to turbidity. They are runoff from highly developed urban areas, agricultural activities, and construction projects (see Figure 6.6).

FIGURE 6.6
Leading sources of ocean shoreline impairment^a, 2000
SOURCE: "Figure 4-12. Leading Sources of Ocean Shoreline Impairment," in 2000 National Water Quality Inventory, U.S. Environmental Protection Agency, August 2002

In general, most of the ocean waters assessed supported the five general-use categories shown for estuaries: aquatic life support, fish consumption, shellfishing, primary contact, and secondary contact. These categories represent summaries of the designated uses and their achievement provided by the states to the EPA. Waters that either support their designated uses only part of the time or do not support their uses at all are considered impaired. Good water quality supports primary contact (swimming without risk to public health) in 85% of the assessed ocean waters (the same percentage for use support in estuaries), and fish consumption (fish safe to eat) in 91% (compared to 52% of use support in estuaries).

In 94% of the waters assessed, the water was considered of good quality, capable of supporting aquatic life (suitable habitat for protection and propagation of desirable fish, shellfish, and other aquatic organisms). In the shellfish harvesting summary (water quality supports FIGURE 6.7
Assessed waters and water quality in tidal estuaries, 2000
SOURCE: "Assessed Waters," in 2000 National Water Quality Inventory, U.S. Environmental Protection Agency, August 2002 a population of bivalves free from toxicants and pathogens that could pose a health risk to people who eat them), 86% of the ocean waters assessed had good water quality that supported this use. In addition, good water quality in 91% of the ocean waters assessed supported secondary contact recreation (people can perform water-based activities such as water skiing and boating without risk of adverse human health effects).

Estuaries

Twenty-three of the twenty-seven coastal states provided data for use in the 2000 National Water Quality Inventory. These twenty-three states assessed 36% of the nation's estuaries. (See Figure 6.7.) Of the 31,072 square miles assessed, 49% supported their uses and 51% were impaired. Figure 6.8 shows the major pollutants in U.S. estuaries. Metals were the most common pollutants, followed by pesticides and oxygen-depleting substances. This pollution came primarily from municipal point sources, urban runoff and storm sewers, and industrial discharges.

FIGURE 6.8
Leading pollutants in impaired estuaries, 2000
SOURCE: "Figure 4-3. Leading Pollutants in Impaired Estuaries," in 2000 National Water Quality Inventory, U.S. Environmental Protection Agency, August 2002

As with the U.S. ocean shoreline, the five general use categories provide important details about the nature of water quality problems in estuaries. In general, most of the waters assessed supported the general use categories. The two use categories that showed the greatest impairment were aquatic life support (52% impairment) and fish consumption (48% impairment). Good water quality in 75% of the estuaries assessed supported use for shellfish harvesting, while 77% of the waters supported secondary contact recreation. Eighty-five percent of the estuarine waters assessed had good water quality for primary contact use.