Ecological and water-quality data were collected at a site on the Coosawhatchie River, South Carolina, as part of the National Water-Quality Assessment Program (NAWQA) of the U.S. Geological Survey (USGS), and an interagency Forested Wetlands Initiative involving the U.S. Forest Service. The Coosawhatchie River is a highly anastomosing blackwater stream flowing through a drainage basin characterized by agricultural land use (42 percent), forested areas (30 percent), and wetlands (24 percent).

Water-quality samples were collected monthly for two years. Additional water samples were collected during summer (low flows), winter (intermediate flows), and storms (high flows). All samples were analyzed for the presence of nutrients, organic carbon, major ions, and suspended sediment. Temperature, conductivity, pH, dissolved oxygen, and alkalinity were measured on site during each collection. Real-time stream discharge was measured and recorded continuously. Seasonal patterns were observed in nutrients, suspended organic carbon, dissolved oxygen, and silica concentrations. Phosphorus concentrations were highest during low streamflow in the late spring and early summer, decreased through the fall, and were lowest during the winter. Ammonia nitrogen concentrations were generally low. A comparison of total and dissolved ammonia-plus-organic nitrogen and ammonia nitrogen concentrations indicated that the majority of the nitrogen was in the dissolved organic form. Nitrate-nitrogen concentrations were generally below 0.15 milligrams per liter. Dissolved oxygen percent saturation and silica concentrations were highest in the winter.

Samples of macroinvertebrates and fish were collected along a 300-meter reach of the river, along with data on habitat and riparian zone structure. Native clams (Elliptio species) were collected and analyzed to determine the concentrations of 21 elements and 26 organochlorine pesticides in tissue. None of the pesticides or pesticide metabolites for which clam tissues were analyzed were detected. Seventy-three percent of the identified individuals in the macroinvertebrate community belonged to 19 of the 148 taxa. Of these 19 taxa, 10 taxa were in the family Chironomidae (Insecta, Diptera). The most numerous organism was a leech, _Placobdella parasitica_ (Say), a parasite of other macroinvertebrate fauna, and a food source for juvenile fish. Twenty-three species of fish, representing ten families and four feeding guilds were collected. The immediate (within 3 meters of the main river channel) riparian flora of the stream reach is dominated by water tupelo (_Nyssa aquatica_) and water elm (_Planera aquatica_).

Sediment samples were collected and processed in the field for analyses of 43 elements and 99 organic compounds. Sediment composition included a number of organic compounds, but their health effect, if any, on aquatic organisms is unknown. Sediments also contained a number of trace element priority pollutants, but concentrations were below threshold levels considered toxic to aquatic organisms.

--- June 1999

To order SANT NAWQA publications, please email or call:

Celeste A. Journey
SANT NAWQA Project Chief
cjourney@usgs.gov
(803) 750-6141