THE SIGNIFICANCE OF 17 BETA-ESTRADIOL IN THE ROCK BRIDGE STREAM/SPRING SYSTEM, MO

17 Beta-estradiol (E2) is the most potent steroidal estrogen (female sex hormone) and is produced endogenously by all mammalian species. High concentrations of E2 can result in adverse health effects (kidney impairment, necrosis, and liver damage) on fish. Even concentrations as low as 25 ng/L have been found to lead to reproductive impairment and feminization of fish resulting in skewed populations. Main sources of high E2 concentrations to the aquatic environment are sewage treatment wastewater and livestock waste. In karst systems, groundwater is particularly vulnerable to surface land use activities because of the direct link between surface and groundwater. When impacted surface water or storm water runoff enters sinkholes, the waters can carry estrogen directly into the karst conduits. As a result of this direct linkage, a number of karst aquifers in Missouri have been impacted with estrogen. This can become significant since many karst springs in Missouri are used as water supply for fish hatcheries, as well as being host to both game and non-game fish, including the endangered cave fish, Amblyopsis rosae.

Rock Bridge Memorial State Park, south of Columbia, MO, is home to the Devil’s Ice Box/Connor’s cave system. The cave consists of one main conduit with a few small side passages; it receives water from a 37.6 km2 karst basin. The upper portion of the drainage basin includes land used for agriculture, while housing developments using septic tank systems are located within the lower basin of the system. Water samples were obtained both upstream from the losing reach and downstream from the spring, and unconjugated E2 concentrations contained in these water samples were determined with ELISA (enzyme-linked immunosorbent assay) kits. E2 concentrations from diurnal sampling events ranged from 14 to 167 ng/L at the spring site, with similar concentrations measured upstream. No diurnal trend was observed. From April to September each year, the cave hosts a community of bats; we have yet to determine if these bats affect the E2 concentrations released to the spring.