New study shows fish respond quickly to changes in mercury depositionSeptember 20, 2007Reducing atmospheric mercury emissions should quickly reduce mercury levels in lake fish, according to a three-year study published this week in the Proceedings of the National Academy of Science. The study showed that an increase in mercury loading at rates relevant to atmospheric deposition resulted in a significant increase in methylmercury production and accumulation in fish in only three years. "This is good news. It means that a reduction in new mercury loads to many lakes should result in lower mercury in fish within a few years," said Cynthia Gilmour, scientist at the Smithsonian Environmental Research Center and a co-investigator in the study. While recent federal and state regulations aimed at reducing mercury levels in fish require reductions in mercury emissions, the potential effectiveness of these controls and the time frame of the response were previously unknown.
Some have speculated that it could take decades to see the impact of emissions reductions on mercury levels in fish. Centuries of human-derived mercury releases to the atmosphere have resulted in elevated amounts of mercury in sediments and soils across most of the globe. If this historical mercury contamination contributes substantially to mercury in fish, reductions in current emissions may have little impact in the foreseeable future. The study, "Mercury Experiment to Assess Atmospheric Loading in Canada and the United States," found that methylmercury (the type that accumulates in fish) was more readily produced from newly deposited mercury than from historical mercury contamination already buried in lake sediments. This means that methylmercury in lakes should decline quickly if mercury deposition is reduced. Additionally, the study team found that mercury added directly to the lake surface was rapidly accumulated into fish, while essentially none of the mercury deposited to the lake's watershed was found in fish after three years. This suggests that lakes should exhibit a two-phase response to load reductions. Initially, mercury in fish should decline rapidly (within years) as deposition to the lake itself is reduced. A slower, more prolonged decline (perhaps decades long) should follow in response to decreases in mercury deposition in the watershed. The study was accomplished through an experimental addition of mercury to a small lake and its watershed at the Experimental Lakes Area, a Canadian federal research reserve. ELA is a remote, protected area set aside for the long-term study of lakes and watersheds, where deposition of mercury is low compared with sites in Europe and the United States. For three years, the mercury load to the lake ecosystem was increased by roughly three times-bringing the total annual mercury load up to a level comparable to that on the east coast of the United States. This large-scale, whole ecosystem approach was important because the complex behavior of ecosystems can be difficult to predict from smaller-scale experiments. To distinguish the mercury they added to the lake from the existing mercury in the study ecosystem, the researchers used a sophisticated analytical method that had never been used in this way at such a large scale. Mercury in the natural environment is made up of seven stable isotopes that do not vary much in proportion to one another. To dose the lake, the scientists used mercury that is heavily enriched in one of those isotopes, enabling them to trace the mercury they added through the complex environmental mercury cycle. Gilmour and her colleagues Andrew Heyes (University of Maryland) and Robert Mason (University of Connecticut) focused on one of the key processes in that cycle, the microbial production of methylmercury, which is produced by natural bacteria in sediments and soils and accumulates in food webs. "It will be important to monitor mercury during the next 20 years to make sure that emissions regulations are effective in reducing mercury deposition," Gilmour said. "If they are, the study suggests that reductions in emissions will result in fairly rapid reduction in risk to people and to ecosystems." Smithsonian | ||||||||||
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Related Methylmercury News Articles Scientists find mercury threatens next generation of loons A long-term study by the Wildlife Conservation Society, the BioDiversity Research Institute, and other organizations has found and confirmed that environmental mercury-much of which comes from human-generated emissions-is impacting both the health and reproductive success of common loons in the Northeast. Waterborne carbon increases threat of environmental mercury Mercury is a potent neurotoxin and a worrisome environmental contaminant, but the severity of its threat appears to depend on what else is in the water. Scientists Estimate Mercury Emissions from U.S. Fires; West Coast and Southeastern States are Major Emitters Forest fires and other blazes in the United States likely release about 30 percent as much mercury as the nation's industrial sources, according to initial estimates in a new study by scientists at the National Center for Atmospheric Research (NCAR). International team shows mercury concentrations in fish respond quickly to increased deposition A joint Canadian-American research team have, for the first time, demonstrated that mercury concentrations in fish respond directly to changes in atmospheric deposition of the chemical. Improved NIST SRM aids lead poisoning detection Lead in goat blood might not be on the top of your shopping list, but for U.S. medical personnel who each year perform more than 2 million human blood measurements, Standard Reference Material (SRM) 955c from the National Institute of Standards and Technology (NIST) can't be beat. Mercury contamination of fish warrants worldwide public warning The health risks posed by mercury contaminated fish is sufficient to warrant issuing a worldwide general warning to the public — especially children and women of childbearing age-to be careful about how much and which fish they eat. Hotspots of mercury contamination identified in eastern North America A US and Canadian research team surveying mercury contamination in fish and birds in the northeastern United States and southeastern Canada has identified five "hotspots" where concentrations of the element exceed those established for human or wildlife health. A silent pandemic: Industrial chemicals are impairing the brain development of children worldwide Fetal and early childhood exposures to industrial chemicals in the environment can damage the developing brain and can lead to neurodevelopmental disorders (NDDs)-autism, attention deficit disorder (ADHD), and mental retardation. Benefits of eating seafood outweigh risks Though some species of fish around the world's are likely to be contaminated with mercury, PCBs and other toxins, the benefits of eating seafood continue to outweigh the risks. Prenatal Exposure To Mercury In Fish Not Associated With Impaired Neurodevelopment (p 1667, 1686) Authors of a longitudinal study investigating a possible link between prenatal mercury exposure from ocean fish and impaired neurodevelopment in children report their latest findings in this week's issue of THE LANCET. The results confirm earlier findings that prenatal exposure to mercury in the Seychelles-where fish consumption is the main component of the local diet-is not associated with impaired neurodevelopment in young children. A research team from the University of Rochester, USA, with colleagues from the Seychelles investigated 779 mother-infant pairs enrolled in the Seychelles Childhood Development Study, established in 1989/1990. Mothers reported high fish consumption-12 meals a w More Methylmercury News Articles |
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