GAINESVILLE, Fla. --- In a rare piece of good news about mercury contamination in the Everglades, a University of Florida researcher has found that levels of the pollutant in wading birds have dropped significantly since 1994.
Scientists and state officials charged with reducing mercury pollution aren't sure of the cause, but the declines may reflect the removal of mercury from commercial products and industrial processes, a trend that began in the late 1980s, they say. The declines also come at a time when efforts by the Florida Department of Environmental Protection to limit mercury emissions from incinerators in Florida are just beginning to bear fruit.
Peter Frederick, a UF associate professor in the department of wildlife ecology and conservation, was the lead investigator in the seven-year study sponsored by the DEP. For the study, he and several graduate students monitored mercury levels in great egret chicks in seven Everglades colonies, or communal nesting sites.
As predators at the top of the food chain, great egrets are good barometers for the herons, ibises, storks and spoonbills that also live in the Everglades, Frederick said. Chicks' parents, which bring them food, hunt within about 15 miles of nests, so chicks are ideal study subjects because the mercury they accumulate comes from surrounding areas.
When birds ingest mercury, they release some of it in their growing feathers. This gave Frederick and other researchers a harmless way to track the chicks' mercury uptake: They caught 20 chicks in each colony each year, plucked a few of their feathers for analysis, and put the chicks back into their nests.
The results surprised and pleased the researchers. The most significant: Between 1994 and this year, average levels in the chicks' feathers dropped 73 percent, Frederick said.
Some natural processes can affect mercury uptake in wading birds. For instance, levels
may rise in dry years because big fish --
Contact: Peter Frederick
University of Florida