Water and Sediment Quality Survey of Threatened and Endangered Freshwater Mussel Habitat in the Ochlockonee River Basin

The U.S. Fish and Wildlife Service (Service) Freshwater Mussels Recovery Plan (USFWS 2003) called for the evaluation of freshwater mussel habitat in the Ochlockonee River of Florida and Georgia to identify areas with factors potentially limiting to mussel life history. Identification of these areas will allow for the implementation of measures to maximize recovery efforts and ensure adequate water quality for these imperiled species. To meet the recovery plan criteria, a coordinated effort among the Service’s Environmental Contaminants Program, the U.S. Geological Survey’s Patuxent Wildlife Research Center, and the Service’s Fisheries Resources Office was conducted. The combined effort of these programs allowed for performance of water chemical analyses, porewater and whole sediment chemical analyses, and porewater and whole sediment toxicity testing. These analyses allowed for the identification of impaired sites and determination of differences between sites that currently support mussels and those that have ceased to support populations. The results further provided an evaluation of potential risk to aquatic species which was used as a preliminary risk estimation for freshwater mussels. The preliminary risk estimation based on degraded water and sediment quality was used for identification and ranking of mussel habitat in need of restoration. Cumulatively, sites posing potential risk to freshwater mussel species achieved an estimated potential risk score of five or greater (below the dam, Little River, and ~3 miles SSE of Cairo, GA). These sites corresponded well with areas that no longer support their historic freshwater mussel populations. Factors contributing to the high risk estimation for these sites were sediment toxicity (porewater and whole sediment), sediment lead, sediment manganese, sediment ammonia, and low dissolved oxygen.