REDIVERSION SALINITY CHANGE IN THE COOPER RIVER, SOUTH-CAROLINA - ECOLOGICAL IMPLICATIONS

A 70% reduction in freshwater discharge through the Cooper River Basin, South Carolina, has provided a unique opportunity to study changes in estuarine plant communities in response to a system-wide increase in salinity. A one-dimensional tidal prism mixing model was used to simulate the changes in the longitudinal salinity distribution which have occurred in the Cooper River since a diversion in 1985 reduced the mean flow from 442 to 130 m3 s-1. Model simulations indicate that a salinity increase of 10-14 parts per thousand has occurred in the region of the river where the marsh plant community shifts from a virtual monoculture of Spartina alterniflora to a more diverse brackish community. The flow reduction and associated salinity increase are expected to result in an increased dominance of the halophyte, S. alterniflora, and a progressive exclusion of the less halotolerant species which currently inhabit this region.