DDT, PCBs, And Invasive Plants - USGS Scientists Examine The Effects Of Contaminant And Invasive Species On Wildlife

September 22, 1998

Tipsheet

From evidence of lingering DDT damage, to questions about artificial wetlands as habitat, to the uses of a dynamic ecosystem evaluation and monitoring tool, USGS scientists will present a variety of wildlife research findings at the annual meeting of The Wildlife Society at the Buffalo Convention Center, Buffalo, N.Y., Sept. 22-26, 1998.

Native Animals Snub Exotic Vegetation and Grazed Areas -- Tues. Sept., 22, session 3

Mammals, reptiles and amphibians, and other animals are signficantly more common in areas covered primarily by native vegetation than in areas covered primarily by exotic vegetation that have also experienced various levels of grazing.

In 1990, researchers began monitoring 450 sample plots to determine the diversity of land animals at the 75,000-acre Golden Gate National Recreation Area near San Franciso. The monitored habitats consisted of coastal grassland, scrub and evergreen woodlands, some of which were under active grazing or had experienced grazing historically.

The prevalence of native animals in previously grazed native vegetation is significant. For example, in one ten-day trapping period, researchers trapped only two species in the previously grazed-exotic vegetation habitat, but they trapped 17 native species on nearby sites dominated by native grasses and shrubs. ("Grazing Succession Plots of the Golden Gate National Parks, California," by Judd A. Howell and Marcia Semenoff-Irving, USGS, Sausalito, Calif. )

DDT May Still be Having an Impact on Cormorants -- Thurs., Sept., 24, session 7b

Although DDT was banned in the U.S. in the 1970s, results of a 1994-1995 study suggest DDT may still be adversely affecting reproduction of the double-crested cormorant. The study examined the effects of organochlorines, including DDE (a degradation product of DDT) and PCBs (polychlorinated biphenyls), on the reproductive success of double-crested cormorants nesting on Cat Island in southern Green Bay, Wis. This research was undertaken to clarify conflicting evidence about the effects of PCB on cormorant reproduction. Researchers monitored cormorants from egg-laying through the departure of young from the nest. Reduced hatching success of cormorant eggs was related to higer amounts of DDE in eggs and to thinner eggshells. ("Effects of Organochlorine Contaminants on Double-Crested Cormorants Nesting in Green Bay, Wisconsin," by Thomas W. Custer and Christine M. Custer, USGS, LaCrosse, Wis.; Kenneth L. Stromborg, U.S. Fish and Wildlife Service, Green Bay, Wis.; Mark J. Melancon, USGS, Laurel, Md.)

The Tree Swallow as Sentinal for PCBs in Aquatic Sediments -- Thur., Sept. 24, session 7b

Tree swallows are an excellent indicator of PCB (polychlorinated biphenyl) contamination in aquatic environments, a recent study suggests. Researchers examined birds exposed to PCBs in field sites with differing concentrations of PCBs as well as in birds exposed in controlled laboratory settings. The study revealed a highly significant correlation between PCB concentrations in tree swallow eggs and nestlings and concentrations found in aquatic sediments.

Tree swallows live in many North American habitats, are easily attracted to nestboxes, and because they feed extensively on aquatic insects, can serve as a non-fish-eating sentinel species for contaminant exposure from the aquatic environment. ("Biomarker Response of Tree Swallows to PCBs," by Mark J. Melancon and Amy L Yorks Kutay, USGS, Laurel, Md.)

Nesting Success of Snowy Plovers on Artificial Wetlands Uncertain -- Sat., Sept., 26, session 24

Although snowy plovers readily use artificial dredge-spoil islands as breeding habitat, a new study shows that over time, snowy plover hatching success in these artificial wetlands substantially declined. Researchers speculate that as predators gradually invade the islands, they feed on eggs and young, causing nest success to decline.

Researchers conducted this study of snowy plover breeding habitats on five islands created in 1995-1996 at Batiquitos Lagoon, near San Diego, to mitigate wetland loss caused by development in southern California. From 1994 to 1997, the number of snowy plover nesting attempts in the lagoon area, including the islands, increased from 5 to 38. The fledgling survival rate increased after the first year, but then dropped below the first year's level by the end of the study period. ("Invasion of Created Habitats by Western Snowy Plovers in Coastal California," by Abby N. Powell, USGS, Fayetteville, Ark.; and Christine L. Collier, USGS, San Diego)

USGS has the BEST System for Ecosystems -- Thurs., Sept., 24, session 7b

The Biomonitoring of Environmental Status and Trends (BEST) program is a significant tool for addressing the effects of contaminants stressing major ecosystems on Department of the Interior lands. One componet of BEST is a toxicological database that can be directly queried by natural resource managers and operated in conjunction with the GIS (geographic information system) to identify pollution "hot spots," generate and test hypotheses, and identify data gaps. The BEST presentation will feature an overview of contaminant exposure, effects, and trends for land animals that reside in estuarine regions in the northeastern United States. ("Identification of Contaminant Trends and Data Gaps for Terrestrial Vertebrates Residing in Northeastern Estuaries of the United States," by Barnett A. Rattner, USGS, Laurel, Md.)

As the nation's largest water, earth and biological science and civilian mapping agency, the USGS works in cooperation with more than 2000 organizations across the country to provide reliable, impartial, scientific information to resource managers, planners, and other customers. This information is gathered in every state by USGS scientists to minimize the loss of life and property from natural disasters, contribute to the sound conservation, economic and physical development of the nation's natural resources, and enhance the quality of life by monitoring water, biological, energy, and mineral resources.
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Note to Editors: To arrange an interview with any of the USGS presenters listed below, contact Casey Stemler at the USGS exhibit area.
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