What are the trends in the extent and condition of coastal waters and their effects on human health and the environment?
Importance of Coastal Waters
As the interface between terrestrial environments and open oceans, coastal waters encompass many unique habitats and serve important human needs. Coastal habitats include estuaries, coastal wetlands, seagrass meadows, coral reefs, mangrove forests, kelp forests, and upwelling areas.
Coastal waters support many fish species and provide breeding habitat for 85 percent of U.S. migratory birds. They also provide habitat for many other organisms such as marine mammals, corals, sea turtles, and submerged aquatic vegetation.
Coastal waters support a wide range of human activities such as tourism, recreation, transportation, and fisheries. Lands on the coast are highly desirable places for people to live.
Coastal Water Extent
The extent of coastal waters—their spatial area—is particularly important with respect to specific types of coastal waters, such as coastal wetlands and coral reefs. Extent can be affected by natural factors, such as erosion and storms. It can also be changed by human activities, such as draining or filling wetlands for development or constructing seawalls or barriers. Channeling rivers can cause land to “sink” in coastal areas that otherwise would be naturally replenished by sediments.
Coastal Water Condition
- Nutrients and pathogens can come from storm water, agricultural runoff, and sewage discharge or overflows. Excess nutrients can cause algal blooms that result in low dissolved oxygen levels, which harm aquatic life. Pathogens (e.g., bacteria and viruses) can affect the health of people who use waters for recreation or eat contaminated fish or shellfish.
- Chemical contaminants can come from sources such as agricultural runoff, industrial activities, and atmospheric deposition of airborne pollutants. Of particular concern to human health are toxic chemicals in consumable fish and shellfish.
- Changes in temperature and salinity can be influenced by weather patterns or the condition of freshwater inputs. These changes can affect habitat quality and the status of native plant and animal populations, and can also influence algal blooms.
- Non-indigenous species can affect the status of native communities. In particular, invasive species can kill or crowd out native populations or otherwise alter coastal watersheds.
- Overharvesting can affect populations of fish, shellfish, marine mammals, and other species.
- Changes in the extent of coastal waters can also affect their condition. For example, beach erosion and wetland loss can affect contaminant and sediment levels. Wetland loss can also affect the condition of the wetlands that remain.
- Four of the indicators (Coastal Benthic Communities, Coastal Fish Tissue, Coastal Sediment Quality, and Trophic State of Coastal Waters) come from EPA's National Coastal Assessment, which collects samples of water, sediment, benthic organisms, and fish from coastal waters across the nation.
- One indicator (Wetlands) shows the results of a long-term survey of the extent of coastal wetlands nationwide.
- The other two indicators focus on regional issues in waterbodies of national significance: Hypoxia in the Gulf of Mexico and Long Island Sound and Submerged Aquatic Vegetation in Chesapeake Bay.
Comprehensive long-term data are not yet available for certain other topics of interest in coastal waters, such as the extent of harmful algal blooms.