The Water Resources Division assisted Lake Mead National Recreation Area staff in contacting experts from around the world to help decide how to handle this problem. An advisory group of these experts was convened to develop strategies for identifying the chemical(s) responsible for the endocrine impacts on the carp’s normal hormonal functioning. At the group’s urging, Shane Snyder, an environmental toxicologist and chemist at Michigan State University, began a study to identify the chemical compounds responsible for the endocrine disruption.
The study results, published in 1998, suggest that natural and synthetic hormones originating in women’s urine are among the culprits. Human female reproductive hormones, including estradiol (natural estrogen) and ethinyl estradiol (the synthetic hormone in the birth control pill), were identified as the initial prime suspects in endocrine disruption of Lake Mead fish. Ethinyl estradiol is much more resistant to breakdown in the environment and in current wastewater treatment systems than are natural estrogens. Other potentially endocrine-active synthetic chemicals in Las Vegas Wash, the site of the study, include butyl tins and perchlorate.
Initial discussions were held with operators of the Las Vegas wastewater treatment plants to determine if remedies are available to remove the estradiol and ethinyl estradiol compounds from treated discharges. However, this treatment process will be difficult and expensive. Instead of focusing on the sewage treatment option, the Park Service will concentrate on more completely documenting the effects of these chemicals in the water column on fish and fish populations. With this goal in mind, the Southern Nevada Water Authority and the National Park Service are supporting a study of the effects of the chemicals on caged fish. In addition, endangered fish studies are being considered; if endangered fish are at risk, managing the level of the disruptive chemicals becomes even more important.
The suspect chemicals (estradiols, organochlorines, and phenols) are changed by the human body into a less estrogenic and more water-soluble form that can move around easily in surface water. Once these chemicals are transported to other media (such as sediments, fish guts, or human guts), they may be changed by bacteria back into the more estrogenic form, which is more hazardous, more endocrine-active, and less soluble (less mobile) than the parent compounds.
As the city of Las Vegas continues to grow rapidly, and as the flow of treated sewage into Lake Mead increases, endocrine disruption and other impacts on water quality and park resources may also grow and will need to be closely monitored and mitigated.
roy_irwin@nps.gov
Senior Contaminants Specialist, NPS Water Resources Division; Natural Resource Program Center, Fort Collins, Colorado
NEW PROBLEM
FOR YELLOWSTONE
CUTTHROAT
Caused by a microscopic parasite of European origin, whirling disease was found in 11 of 41 Yellowstone Lake cutthroat trout sampled during the fall. The disease attacks the cartilage of some fish species, causing whirling behavior and often death either from the disease itself, starvation because of inability to feed normally, or increased vulnerability to predators such as the nonnative lake trout, which were first confirmed in Yellowstone Lake in 1994. Park biologists do not know what effect the disease will have on the native cutthroat population. Indeed, many questions remain unanswered, such as why some fish are more susceptible than others, what role alternate hosts play in disease transmission, and how the disease can be controlled.
Award-Winner Profile
KENT TURNER HONORED
The 1997 Director’s Award for Natural Resource Management was given to Kent Turner, chief of resource management at Lake Mead National Recreation Area (Nevada and Arizona). An effective administrator, Kent has developed a professional and respected resource management staff. Through their efforts, park natural and cultural resources are now widely recognized as both important and varied. Under his guidance, Kent’s staff devised and implemented monitoring strategies for the relict leopard frog, desert tortoise, and desert shrub plant communities. Seventy percent of the park boundary is now protected through partnerships with adjacent land managers. A burro management plan is complete and more than 900 burros have been removed from the park. Nineteen springs and eight other sites are free of nonnative tamarisk, and a native plant nursery has been established. This robust resource management program, assembled and nurtured through Kent’s energies and support, has strengthened partnerships with park neighbors and improved the information upon which management decisions are made.
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