RESPONSES OF OHIO RIVER AND LAKE-ERIE DREISSENID MOLLUSKS TO CHANGES IN TEMPERATURE AND TURBIDITY

To predict possible effects of global climatic change (via changes in ambient water temperatures and suspended sediments) on two exotic biva lves (zebra mussel, Dreissena polymorpha, and quagga mussel, Dreissena bugensis), we evaluated survival and growth at three temperatures (am bient, ambient + 2 degrees C, and ambient + 4 degrees C) and two turbi dities (ambient and twice ambient) in outdoor tanks for approximately 3 months during both warm and cool seasons. We compared responses of z ebra and quagga mussels from southwestern Lake Erie and zebra mussel f rom the Ohio River at Louisville, Kentucky. Experimental increases in temperature significantly enhanced growth rates in fall - early winter but not during summer - early fall. Elevated temperatures increased m ortality in the warm season but not in the cool season. Zr:bra mussel survived better (especially the Ohio River population) than did quagga mussel at high temperatures. Inorganic turbidity had few detectable e ffects; relationships, where significant, varied with temperature and species. Based on these experiments and related laboratory studies, we predict that populations of Dreissena in the Ohio River and farther s outh will suffer overall if water temperatures increase. In contrast, more northern populations of Dreissena will probably benefit from pred icted climatic change and may extend their range to higher latitudes a nd altitudes.