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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Unionid Ecology
THE EFFECTS OF A SEVERE DROUGHT ON FRESHWATER MUSSEL ASSEMBLAGES IN SOUTHWEST GEORGIA.
S.W. Golladay, M. Kearns, J.M. Battle, and P. Gagnon. J.W. Jones Ecological Research Center, Rte 2 Box 2324, Newton GA USA 31770
Freshwater mussel assemblages in the Flint River Basin of Southwest Georgia are among the richest in the world. Historically, 29 species including 7 endemics occurred in the Flint Basin. A drought during the summer of 2000 caused record low flows and many perennial streams dried or became intermittent. Pre-drought surveys conducted in 1999 allowed us to assess the impact of the drought on mussel assemblages. During 2001, 20 stream reaches which had abundant or diverse mussel assemblages were resurveyed. Where possible, study areas were classified as flowing or non-flowing during the drought. Taxa richness was stable across the drought, only two of the non-flowing sites showed a loss of more than three taxa. Mussel abundance at sites classified as non-flowing showed significant declines (median value 80% decrease) compared to flowing sites (median value 5% increase). Riffle preferring taxa often showed the greatest declines. Generally, greatest declines in mussel abundance occurred in the mid-reaches of the major tributaries of the lower Flint River. These reaches depend on a regional aquifer system, heavily used for irrigation, to maintain baseflows. Declines in mussel populations appear to be associated with unusual climatic conditions and increasing demand on the regional aquifer system.
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