Monitoring Cavefish Populations and Environmental Quality in Cave Springs Cave, Arkansas

Cave Springs Cave, Benton County, Arkansas, was monitored from October 1997 to June 1998 to determine the chemical and physical environmental quality and the status of the population of threatened Ozark cavefish, Amblyopsis rosae. The majority of the chemical parameters measured were indicative of adequate environmental quality in the Cave Springs Cave ecosystem. However, several significant problems were revealed. A trend analysis of known water quality studies of this cave complex suggests that many organic and inorganic chemicals have increased in concentration in the last 14 years. This ecologically sensitive water body did not meet Arkansas water quality regulations for fecal coliform densities, and copper, selenium, and lead concentrations exceeded limits for exposure to aquatic life. The geometric mean total coliform count for base flows was 500 MPN/100ml, and during the March storm event, coliform densities exceeded 20,000 MPN/100ml. When compared to the national primary drinking water regulations, this spring water exceeds the maximum contaminant levels (MCL) for turbidity, nitrite, total coliforms, and Escherichia coli, and approaches the MCL’s for copper and zinc. During the March storm event, Escherichia coli densities exceeded 5,000 MPN/100ml. During the June storm event, nitrite levels reached 2 mg/L, twice the MCL for national drinking water standards. Nitrite toxicity is known to cause severe anemia in fishes and damage their tissues. One semi-volatile organic, Di (2-ethylhexyl) phthalate (DEHP), was found in significant concentration (500 ug/kg) in resident crayfish tissue. DEHP is known to bioaccumulate in fish tissue, and cause reproductive damage and reduced fertility in fish. A visual survey was performed on January 25, 1998, and 106 cavefish were sighted. This survey indicated a 30% decline in the Cave Springs Cave population. A comparison of base-flow sampling results at two different locations -- upstream and downstream of bat rookeries -- indicates that the majority of coliform bacteria are not attributed to bat guano. These findings suggest that bacteria are being imported into the cave stream from the recharge zone. The high nitrite, total coliform, and E. coli counts suggest that septic system leakage or the land application of animal waste is involved. Continued water quality monitoring and surveys of the Ozark cavefish population are recommended. Future monitoring should focus on storm events and parameters that measure pollutants originating from the recharge zone and their effect on the cave ecosystem. As well, investigation into the nature of the pollutants from the recharge zone is suggested