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‰ has occurred in the region of the river where the marsh plant community shifts from a virtual monoculture ofSpartina 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.