Category Archives: 2000s
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As long-lived fish-eating predators at the top of the food chain, bottlenose dolphins experience biomagnification of contaminants (i.e., as prey organisms are consumed, pollutants can accumulate in the predator, increasing in concentration with each step up the food chain). These mammals live year-round in Charleston waters and can act as ideal sentinels, reflecting spatial and temporal trends in the health of the marine environment.

Studies conducted by Dr. Patricia Fair and colleagues have indicated that total PCB, DDT and PBDE blubber concentrations and blood PFC levels in Charleston dolphins are among the highest reported values that have been measured in marine mammals! A total of 88% of the dolphins sampled from Charleston Harbor and the rivers and creeks of our watershed in one study exceeded the toxicity threshold for PCBs. When 82 dolphins from estuarine waters near Charleston were evaluated for health, 50% showed evidence of environmentally related symptoms and diseases. Dr. Fair and colleagues are now conducting a monitoring program measuring PFCs and other pollutants in the sediments at 42 sites in our watershed.

The high levels of organic contaminants detected in our local sentinel dolphins have raised concerns about the African-American Gullah people of the Sea Islands whose diet, like the dolphins, includes local fish. An ongoing study led by Dr. Diane Kamen at the Medical University of South Carolina is focusing on Gullah people at risk of developing the autoimmune disease lupus. Preliminary results indicate that PFCs may play a pathogenic role in triggering the disease. Learn more about the sentinel species.

The abundant resources of the Ashley-Cooper basin fuel an enormous amount of economic activity, including recreation (e.g., swimming and sunbathing , kayaking and canoeing, motor boating, fishing, stand-up paddle boarding, surfing and kiteboarding), tourism, and commercial fishing. The results of a survey conducted by the South Carolina Dept. of Parks, Recreation and Tourism indicated that nearly two-thirds of the state’s adults used South Carolina’s beaches and over one-third participated in freshwater fishing in 2005! The number of saltwater recreational licenses nearly doubled from 2006 to 2010 when 208,204 were sold. Boating is so popular that it is estimated that there is one boat for every 12 people in the state! Learn more about the economics of the Charleston Harbor watershed.

As humans move into our coastal watershed and change the way land is used, the ability of estuarine habitats to function normally is challenged. The Charleston Metropolitan Area (Charleston-North Charleston-Summerville) is one of the 10 fastest growing metropolitan areas in the US. In Charleston, for example, the population grew by 40% from 1973 to 1994 while size of the urban area grew by 240%, creating urban sprawl and greatly increased impervious land cover (e.g., roads, sidewalks, driveways and parking lots that prevent water from being absorbed into the soil). The size of the urban area is expected to increase to 868 square miles by 2030, covering 65 percent of the land area.

Tidal creeks in particular are intimately linked to human land-based activities through the stormwater that runs off into them from developed land and impervious surfaces, carrying with it a cocktail of pollutants from gasoline and oil, fertilizers, pet wastes, sediments, etc. SCECAP (South Carolina Estuarine and Coastal Assessment) is an ongoing joint state and federal program that assesses the health of our coastal habitat, including our sensitive tidal creeks. Data from 1999-2008 has been analyzed and, for that period, the rivers draining into Charleston Harbor showed a persistent pattern of degraded habitat quality (based on water and sediment quality as well as the biological community). This is likely the result of a combination of historical industrial activity and high-density urban development. Learn more about human impacts in our watershed.

Mercury is a poisonous neurotoxin that enters the atmosphere primarily via coal-fired power plants. It can be carried great distances until it is deposited by wind and rain on land and water where it can enter the food chain. In South Carolina, most rivers and lakes have mercury-contaminated fish.  In addition to issuing general consumption advisories, the state has issued guidelines regarding consumption of freshwater and certain salt water fish for high risk groups, including women of child-bearing age and children under 14, groups which represent 43% of the South Carolina’s population.  For a complete list of up-to-date fish consumption advisories and information for individuals in at risk groups, see:  HYPERLINK “https://www.scdhec.gov/environment/water/fish/” https://www.scdhec.gov/environment/water/fish/.

Scientists have studied both local diamond back terrapins and bald eagles as mercury sentinel organisms, animals that can alert us to pollution impacts in the environment. As predators, their bodies accumulate mercury through biomagnification (a process which increases pollutant concentration with each step up the food chain). Learn more about mercury in our waterways.

Toxic chemicals are a significant “stressor” for our fresh and estuarine waterways. Types of pollutants include: (1) organic chemicals like polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and pesticides like DDT; (2) heavy metals like lead and mercury; and (3) “emerging contaminants” like polybrominated diphenyl ethers (PBDEs) and perflourinated chemicals (PFCs) that have not traditionally been monitored or regulated. Pharmaceuticals and personal care products (PPCPs) are also sources of pollutants. Such contaminants are being found worldwide in aquatic environments, including the rivers and estuarine waters of the Ashley/Cooper River Basin.

Key local organisms can help us to understand what potential health and environmental risks these pollutants pose and whether the risks are increasing or decreasing over time.  These organisms are called “sentinel species“.  The results of these sentinel studies (Dolphins, Loggerhead Sea Turtles, Bivalves, Bald Eagles, Diamondback Terrapins) indicate that the toxic chemicals that enter the Ashley/Cooper River Basin and move downstream to Charleston Harbor are finding their way via the food chain into both wildlife and humans, some at concentrations that are health-threatening. Learn more about toxic pollutants in our waterways.