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PT13 Aquatic Ecotoxicology I
(PT203) What factors impact freshwater molluscan survival in the Conasauga River?
Sharpe, A1, Hofelt, C1, Gregory, J1, Johnson, P2, Guthrie-Nichols, E1, 1 North Carolina State Univeristy, Raleigh, NC, USA2 Tennessee Aquarium Research Institute, Cohutta, GA, USA
ABSTRACT- Recent biological inventory data shows a consistent decline in molluscan abundance and biodiversity in the Conasauga River Basin in Northwest GA. The river is impacted by various land uses that include row crop, livestock operations, urban impacts, recreational human uses, and transportation corridors. Preliminary toxicity screening (Vibrio fischeri and the Flash Luminescent Assay) indicated acute toxicity of river sediments, particularly at low flow events. One time sampling may not always capture the full impact due to various meteorological events and changing land use patterns. Additional watershed assessment includes water quality measurements, toxicity screening, snail and sediment analysis by stable nitrogen isotope ratio analyses (IRMS), permeable membrane devices (PMD), and polar organic chemical integrative samplers (POCIS). Preliminary data suggests that a shift to livestock and row crop land-use is correlated with increased water nutrient levels and changes in 15N signatures in snails and sediments. Sediment 15N has a positive Pearson correlation coefficient (p=0.03; <0.05,n=10) to total kjedahl nitrogen (TKN), and snail 15N has a positive relationship (p=0.07; <0.05,n=8) to total kjedahl nitrogen (TKN). 15N of sediment shows an inverse relationship to ammonium concentrations. Sediment 15N displays a similar relationship with nitrate+nitrite and ammonium levels. Additional efforts will determine the 15N for nitrate to determine if enriched 15N in snails and sediment derives from ammonium or nitrate. The impact of organic and inorganic contaminants on aquatic mollusk populations will require more field measurements and laboratory assays using a surrogate snail species in order to narrow causative factors for molluscan decline.
Key words: irms, freshwater snails, water quality assessment
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