Effects of Organic Pollution on an Appalachian Cave: Changes in Macroinvertebrate Populations and Food Supplies

Density of troglobitic crustaceans and levels of potential food sources were compared in reference pools and pools polluted by septic system effluent in Banners Corner Cave, Virginia. Data from four physicochemical variables indicated slight to high pollution in five pools compared with two unpolluted pools. Polluted pools had high levels of conductivity, nutrients and fecal coliforms. Highly polluted pools also had decreased dissolved oxygen levels. Isopods (Caecidotea recurvata) were absent from highly polluted pools. Highest isopod density (up to 74.6/M2) occurred in slightly and moderately polluted pools. Amphipods (Stygobromus mackini) were absent from all polluted pools. Fungal biomass was negligible in all pools. Bacterial biomass accounted for a greater proportion of sediment total organic matter (TOM) in polluted pools, but there was little overall increase in TOM in polluted pools. Results of a laboratory growth experiment suggest that isopods can use bacteria from septic effluent as a food. However, presence of coarse particulate matter, not organic enrichment by septic system effluent, was the most likely cause of high isopod density in some pools. Septic system effluent may provide additional food to the aquatic community in Banners Corner Cave, but generally was damaging to the system.