A comparison of regional mercury atmospheric deposition data with water, yellow perch, and dragonfly larvae samples from lakes in Voyageurs National Park indicates that decreases in mercury emissions resulted in mercury reduction in water from these remote lakes, but mercury declines in biota were significant in only one of three lakes, likely because resident biota integrate exposure over much longer time periods.
Mercury, a pervasive environmental contaminant, is a concern for human and wildlife health. Whereas mercury emissions have increased globally, mercury releases to the environment in the United States and Canada have decreased since 1990. However, questions remain about whether the decreases in atmospheric deposition have equated to decreases in bioaccumulation of mercury in fish from remote lakes and rivers where atmospheric deposition is the predominant source of mercury.
In response to these questions, U.S. Geological Survey and National Park Service scientists investigated and report on one of the longest known multimedia datasets for mercury. The dataset included aqueous total mercury, methylmercury, and sulfate from near-surface lake-water samples from four lakes in Voyageurs National Park in northern Minnesota. The dataset also included total mercury in aquatic biota from the same lakes, as well as atmospheric mercury deposition from two regional sites.
Mercury deposition at the regional sites decreased by an average of 22 percent from 1998 to 2018. Much of these decreases occurred prior to 2009, with relatively flat trends since 2009. In the four lakes, aqueous methylmercury concentrations declined by an average of 44 percent and aqueous total mercury declined by an average of 27 percent (2001–18). Near-surface aqueous methylmercury may be responding to a decline in atmospheric mercury deposition as well as a decline in sulfate deposition, which is an important driver of mercury methylation in the environment.
For the three lakes with long-term biomonitoring (2000–18), temporal patterns in yellow perch (Perca flavescens) and dragonfly larvae (Odonata, Anisoptera) total mercury concentrations declined significantly in only one lake. Two lakes had initial declines until about 2010, corresponding to the initial declines in atmospheric deposition. Results from this study indicate that regional-scale decreases in mercury and sulfate emissions have resulted in reduced mercury concentrations in local lake water. Conversely, biological tissues integrate exposure over much longer time periods, and owing to the large pool of mercury in these lake systems, reduction of mercury in biota may take longer.
This research was funded in part by the U.S. Geological Survey Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology), which is part of the U.S. Geological Survey Ecosystems Mission Area. Additional funding for the manuscript was provided by the National Park Service. Funding for some data collection and analysis was provided by several agencies and programs, including the U.S. Forest Service, U.S. Environmental Protection Agency, Minnesota Pollution Control Agency, University of Minnesota, University of Wisconsin at LaCrosse, and the Great Lakes Restoration Initiative.
See below for related science.
Bioaccumulation of Mercury in Fish Varied by Species and Location in the Chesapeake Bay Watershed—Summary of Existing Data and a Roadmap for Integrated Monitoring
Flood Redistributes Mercury in Grand Canyon Aquatic Food Webs
Dragonfly Larvae are Effective Bioindicators of Mercury Exposure in Fish and Amphibians—Results of Citizen Science in 100 National Parks and Protected Places
Food Web Changes Dampen Expected Reductions in Lake Trout Mercury Levels in Lake Michigan—Invasive Species Play Major Role
Mercury Isotope Ratios used to Determine Sources of Mercury to Fish in Northeast U.S. Streams
Science to Help Understand Exposure and Toxicological Effects of Environmental Mercury to Representative Birds
Roadmap to Understanding Factors Influencing Mercury Exposure and Adverse Health Effects
North American and European Atmospheric Mercury Declines Explained by Local and Regional Emission Reductions
New Tool to Track Sources and Exposure Pathways of Mercury in the Environment — Application for Predatory Fish in the Great Lakes
Comprehensive Assessment of Mercury in Streams Explains Major Sources, Cycling, and Effects
- Overview
A comparison of regional mercury atmospheric deposition data with water, yellow perch, and dragonfly larvae samples from lakes in Voyageurs National Park indicates that decreases in mercury emissions resulted in mercury reduction in water from these remote lakes, but mercury declines in biota were significant in only one of three lakes, likely because resident biota integrate exposure over much longer time periods.
Sources/Usage: Public Domain.Mark Sandheinrich and Sean Bailey of the University of Wisconsin - La Crosse sampling fish from a canoe on Shoepack Lake in Voyageurs National Park. Mercury, a pervasive environmental contaminant, is a concern for human and wildlife health. Whereas mercury emissions have increased globally, mercury releases to the environment in the United States and Canada have decreased since 1990. However, questions remain about whether the decreases in atmospheric deposition have equated to decreases in bioaccumulation of mercury in fish from remote lakes and rivers where atmospheric deposition is the predominant source of mercury.
In response to these questions, U.S. Geological Survey and National Park Service scientists investigated and report on one of the longest known multimedia datasets for mercury. The dataset included aqueous total mercury, methylmercury, and sulfate from near-surface lake-water samples from four lakes in Voyageurs National Park in northern Minnesota. The dataset also included total mercury in aquatic biota from the same lakes, as well as atmospheric mercury deposition from two regional sites.
Sources/Usage: Public Domain.Sample of dragonfly larvae in water in bottom of zip-lock plastic bag, held at horizon level with lake. At Sand Point Lake in Voyageurs National Park. Mercury deposition at the regional sites decreased by an average of 22 percent from 1998 to 2018. Much of these decreases occurred prior to 2009, with relatively flat trends since 2009. In the four lakes, aqueous methylmercury concentrations declined by an average of 44 percent and aqueous total mercury declined by an average of 27 percent (2001–18). Near-surface aqueous methylmercury may be responding to a decline in atmospheric mercury deposition as well as a decline in sulfate deposition, which is an important driver of mercury methylation in the environment.
For the three lakes with long-term biomonitoring (2000–18), temporal patterns in yellow perch (Perca flavescens) and dragonfly larvae (Odonata, Anisoptera) total mercury concentrations declined significantly in only one lake. Two lakes had initial declines until about 2010, corresponding to the initial declines in atmospheric deposition. Results from this study indicate that regional-scale decreases in mercury and sulfate emissions have resulted in reduced mercury concentrations in local lake water. Conversely, biological tissues integrate exposure over much longer time periods, and owing to the large pool of mercury in these lake systems, reduction of mercury in biota may take longer.
This research was funded in part by the U.S. Geological Survey Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology), which is part of the U.S. Geological Survey Ecosystems Mission Area. Additional funding for the manuscript was provided by the National Park Service. Funding for some data collection and analysis was provided by several agencies and programs, including the U.S. Forest Service, U.S. Environmental Protection Agency, Minnesota Pollution Control Agency, University of Minnesota, University of Wisconsin at LaCrosse, and the Great Lakes Restoration Initiative.
- Science
See below for related science.
Bioaccumulation of Mercury in Fish Varied by Species and Location in the Chesapeake Bay Watershed—Summary of Existing Data and a Roadmap for Integrated Monitoring
Fish mercury data from State monitoring programs and research studies within the Chesapeake Bay were compiled and summarized to provide a comprehensive overview of the variation in fish mercury concentrations among species and habitats within the watershed. These data are put into context with existing health benchmarks for humans, birds, and fish. Scientists also provide a roadmap for an...Flood Redistributes Mercury in Grand Canyon Aquatic Food Webs
Scientists coupled the concepts of energy flow through food webs with measurements of mercury in organic matter and animals to estimate mercury fluxes and fate during an experimental flood in the Colorado River. The flood redistributed mercury in simple, upstream food webs but not in more complex, downstream food webs.Dragonfly Larvae are Effective Bioindicators of Mercury Exposure in Fish and Amphibians—Results of Citizen Science in 100 National Parks and Protected Places
Mercury concentrations were measured in dragonfly larvae across more than 450 sites in 100 national parks and protected places as part of a partnership among Federal agencies, academic researchers, and more than 4,000 citizen scientists. Mercury concentrations in dragonfly larvae were positively correlated with mercury concentrations in fish and amphibians living in the same aquatic environments...Food Web Changes Dampen Expected Reductions in Lake Trout Mercury Levels in Lake Michigan—Invasive Species Play Major Role
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Mercury isotope analyses were used to distinguish different sources of mercury to fish in 23 streams along a forested-rural to urban-industrial land-use gradient in the Northeastern United States. The use of mercury isotope measurements in fish tissue allow for distinguishing different sources of mercury that are bioaccumulating into the food web. Mercury isotope signatures in fish in forested...Science to Help Understand Exposure and Toxicological Effects of Environmental Mercury to Representative Birds
Exposure and toxicity of environmental mercury to birds can be enhanced or lessened due to the available sources and forms of mercury and other species dependent factors such as life stage, migratory patterns, foraging and nesting behaviors, transfer of mercury from mothers to eggs, and sex. For example, mercury exposure can lead to sublethal toxicological effects that can influence parental...Roadmap to Understanding Factors Influencing Mercury Exposure and Adverse Health Effects
In a comprehensive overview, scientists explain that human and wildlife exposure and toxicological responses to mercury are dependent on factors that operate across global, individual, and molecular scales. They provide a roadmap for unified research to facilitate a better understanding of human and wildlife health risks from mercury exposure.North American and European Atmospheric Mercury Declines Explained by Local and Regional Emission Reductions
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The US Geological Survey (USGS) and collaborators at the University of Wisconsin-Madison have developed a new tool for attributing (fingerprinting) mercury sources to the Great Lakes. This new fingerprinting tool helps resource managers understand which mitigation strategies will be most effective for reducing mercury loading and exposure to fish and wildlife.Comprehensive Assessment of Mercury in Streams Explains Major Sources, Cycling, and Effects
A new USGS report, Mercury in the Nation's Streams—Levels, Trends, and Implications, presents a comprehensive assessment of mercury contamination in streams across the United States. It highlights the importance of environmental processes, monitoring, and control strategies for understanding and reducing stream mercury levels. This report summarizes selected stream studies conducted by the U.S... - Publications