Portail d'accès aux sources et services d'information agricole

Playa Lakes of the Texas High Plains: A contaminants survey & assessment of biological integrity

In response to increased interest in the quality of playa lakes and their recognition as valuable wildlife habitat, the Arlington Field Office of the U.S. Fish and Wildlife Service initiated a multi-year contaminants survey of playa lakes of the high plains of Texas in 1989.

The study concluded in 1992 with additional laboratory analyses of remaining plant and invertebrate samples. Highlights include the following: o Playa lakes serve as critical resting, wintering, and breeding habitat for several species of waterfowl, wading birds, shorebirds and other aquatic birds. Very high concentrations of arsenic were found in some playa lake sediment samples downstream of various land uses; only salt playas showed markedly lower concentrations. Potential sources of the arsenic include natural soil and rock erosion as well as arsenical pesticides. Zinc and copper were also elevated in some playa sediments. Potentially harmful concentrations of polycyclic aromatic hydrocarbons and other oil compounds were found in sediments near a brine discharge facility at Cedar Lake. This poses a potential problem for sandhill cranes and other waterbirds which sometimes make extensive use of Cedar Lake. A rapid bioassessment method to measure the degree of impairment at playa lakes surrounded by eight different land uses was developed and compared with accompanying contaminants data. The method used data on macroinvertebrates, zooplankton, plants, aquatic vertebrates, and birds. The rapid bioassessment method involved development of an Index of Biotic Integrity (IBI). The IBI demonstrated that there are trenchant differences among the various types of playa lakes surveyed. Aquatic communities in playas were clearly impaired by cattle feedlot wastes. The aquatic communities in playas receiving municipal effluents or brine disposal were also impaired, but to a lesser degree than those receiving feedlot wastes. There was a profound decrease in species richness at playas receiving feedlot wastes compared to other playas studied. Although playas receiving runoff from feedlots may be more similar to oil brine ponds than normal playas, they get very heavy bird use. Birds seem to be attracted to them because they provide a source of open water that does not freeze readily as well as food in the form of cattle feed and pollution tolerant invertebrates such as certain dipteran larvae. The potential bird hazards at feedlots are neither as immediate nor obvious as they are in oil pits. It will be difficult (and may require complex research) to fully determine the degree of hazards to birds. Playas fed by irrigation return flow from corn crops had a fairly diverse assemblage of invertebrates and plants. However, increasingly these "relatively clean" corn playas are drying up as farmers are changing over to more efficient irrigation methods that produce less runoff. The following potential playa lake hazards to migratory birds require more study: (1) concentrations and impacts of currently used pesticides which are not yet on routine Fish and Wildlife Service scans (includes synthetic pyrethroids, pass-through pesticides, "non-routine" feed additives, and breakdown products of all of the above); (2) exposure to the disease vector for avian cholera, and combinations of factors conducive to avian cholera; and, (3) effects of unbalanced, un-natural diet at feedlot and human sewage playas.

Général
Type: 
Belongs to network: 
Geographic
Country where the service is managed: 
États-Unis d'Amérique
Networks
agINFRA The RING is part of the agINFRA project EC 7th framework program INFRA-2011-1.2.2 - Grant agr. no: 283770