A long-term study by the Wildlife Conservation Society, the BioDiversity Research Institute, and other organizations has found and confirmed that environmental mercury from human-generated emissions is damaging the health and reproductive success of common loons in the Northeast.
The results of the 18 year study on loons appear in the most recent edition of the journal "Ecotoxicology."
"This study demonstrates how top predators such as common loons can be used as the proverbial canaries in the coalmine for pollutants that concern humans as well," said David Evers of the BioDiversity Research Institute, lead author of the study. "Our findings can be used to facilitate national and global decisions for regulating mercury emissions from coal-burning plants and other sources."
Metallic mercury and inorganic mercury compounds enters the air from mining ore deposits, burning coal and waste, and from manufacturing plants and falls into bodies of water such as the northern lakes inhabited by loons.
Methylmercury is formed in water and soil by bacteria, and this methylmercury builds up in the tissues of fish. Larger and older fish tend to have the highest levels of mercury. Since loons are fish-eating birds, they ingest high concentrations of mercury.
The common loon (Photo by Stephen Lang courtesy Wisconsin DNR)
The human nervous system is very sensitive to all forms of mercury. Exposure to high levels of metallic, inorganic, or organic mercury can permanently damage the brain, kidneys, and developing fetus. The study was conducted to determine its effects on loons.
The study uses data from nearly 5,500 samples of blood, feathers, and eggs collected from captured and released loons from some 80 lakes in Maine, New York, New Hampshire, and other states and provinces.
With behavioral observations from 1,529 loon territories between 1996 and 2005, the researchers made correlations between the behaviors of individual birds and their levels of methylmercury, the most toxic form of mercury that accumulates up the food chain.
Loons with high levels of mercury were found to spend some 14 percent less time at the nest than normally behaving birds. Unattended nests have a higher rate of failure due to either chilling of the eggs or predation by minks, otters, raccoons and other egg robbers.
High levels of mercury were found in about 16 percent of the adult population in the study area.
Researchers found that loon pairs with elevated mercury levels also produced 41 percent fewer fledged young than loons in lakes relatively free of mercury.
Other behavioral impacts due to elevated mercury were sluggishness, resulting in decreased foraging for fish by the adults for both themselves and for chicks.
In addition to behavior, the concentration of mercury in loons has physical impacts as well.
Researchers found that loons with high mercury loads have unevenly sized flight feathers. Birds with wing asymmetries of more than five percent must expend 20 percent more energy than normal birds to fly, a deficiency that may impact their ability to migrate and maintain a breeding territory.
"This study confirms what we've long suspected - mercury from human activities such as coal-burning power plants is having a significant negative impact on the environment and the health of its most charismatic denizens, and potentially, to humans, too," said Nina Schoch of the Wildlife Conservation Society's Adirondack Program.
"Thus, it becomes even more urgent for the EPA to propose effective national regulations for mercury emissions from power plants that are based on sound science," she said.
Many northeastern states have implemented stringent mercury emission rules, but a nationwide regulation has yet to be passed.
The U.S. District Court of Appeals recently struck down the U.S. Environmental Protection Agency's proposed cap-and-trade rule for mercury emissions from coal-fired power plants, which critics say would have led to localized "hotspots" of mercury.
Schoch says, "The ecological impacts of mercury identified in this study illustrate the need for comprehensive, national regulations to limit mercury emissions."
Copyright Environment News Service (ENS) 2008. All rights reserved.