plankton community of an acid blackwater South Carolina power plant impoundment

Robinson Impoundment was an acid blackwater system, created in 1959 by damming Black Creek (a tributary of Pee Dee river), in the South Carolina sandhills. The pH ranged from 3.4 to 5.9. The impoundment was divided by a causeway into an upper area (narrow, shallow, high flow rate, and high in periphytic and rooted aquatic macrophyte vegetation) and a lower area (wide, deep, many shoreline sandy areas and little macrophyte vegetation). Primary productivity was generally low, but even lower in the upper area. The dominant phytoplankton was Chlorophyceae, and zooplankton was dominated by copepods. Plankton density decreased with a decrease in pH from 5.5 to 4.4 over 2 years. Power-plant thermal discharge had no overall negative effects spatially. Zooplankton predation could control phytoplankton seasonal community structure.