Sabrina Novak
Sabrina Felicitas Novak, Current and Historic Freshwater Mollusk Distributions of the Upper Coosa River Basin
Faculty Chair: Dr. Mark Schorr (UTC) and Dr. Paul Johnson (Tennessee Aquarium), co-chairs
This thesis contains summary data from all Tennessee Aquarium Research Institute (TNARI) survey activities of freshwater mollusks within the upper Coosa River basin (UCRB) from 1998 to 2003. Survey results of 4 different TNARI studies, a total of 515 separate collections, are presented. My component of the study examined 231 sites primarily in the Coosawattee and Etowah river basins in 2002 - 2003. In addition to the 231 sites surveyed, a large database was constructed from natural history museum records to evaluate temporal changes in species richness and distribution across the UCRB. Of 43 mussel and 33 snail species reported from the UCRB, TNARI surveyors found 35 mussel and 26 snail species that remain in small, highly fragmented populations. Three snail species were not previously recorded from the UCRB. Mollusk species richness losses averaged 39% across the 8 sub-basins with reliable data. Species losses (mussels and snails combined) were greatest in the Chattooga River (63%), Etowah River (54%), Oostanaula River (49%), and Coahulla Creek (47%) basins. Species losses were lowest in the Terrapin Creek (19%), Conasauga River (31%), and Armuchee Creek (38%) basins. The number of federally-listed species was greatest in the Conasauga River Basin (6 listed, 1 candidate spp.), Holly Creek, (4 listed spp.), and in the Coosa River, Weiss Reservoir bypass (2 listed spp.). Overall, freshwater mussel ranges were reduced for 86% of the species, and species richness declined 48% across the UCRB (4 spp. extinct and 5 spp. extirpated). Freshwater gastropods also suffered dramatic range reductions (42%) and species losses (4 spp. extinct and 2 spp. extirpated). The sub-drainage with the highest CPUE for mussel species in its tributaries was Terrapin Creek, and the highest mainstem CPUE was the Oostanaula River. Mussel CPUE abundance was highest in the tributaries of Big Cedar Creek and the Coosa River, Weiss Reservoir bypass. CPUE for total snail species was highest in the mainstem Chattooga and Coosawattee rivers tributaries. In addition to the species losses in the UCRB, 4 mussel and 6 snail species are now limited to the study area. Because many remaining species are restricted to small isolated populations, further extinctions and extirpations are expected. Although quantitative habitat evaluation was not a part of this study, channel destabilization, non-point source runoff, eutrophication, dewatering of tributaries and sediment toxicity appear to be major causes of species loss. Weiss Reservoir bypass on the mainstem Coosa River has the greatest potential for mollusk species restoration, and a minimum flow restoration schedule is currently under development. Holly and Terrapin creeks have the best restoration potential of any tributary systems in the UCRB.
