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-rural areas indicated atmospheric sources of mercury. In contrast the isotope signatures in fish in urban-industrial areas are indicative of past (legacy) and present local sources.
Mercury in fish tissues is an important issue due to perceived and established health concerns. In streams within the Northeastern United States, mercury levels in fish tissue frequently exceed concentrations associated with toxicity to humans and wildlife. These streams receive mercury in varying proportions from distant atmospheric deposition as well as from local ongoing and legacy point sources, making it difficult to understand the sources of mercury in fish. Without this information it is difficult to link shifts in fish mercury concentrations directly back to changes in mercury source management and mitigation efforts.
U.S. Geological Survey (USGS) scientists provided a tool to differentiate between mercury sources in both sediments and fish using mercury stable isotope analysis. They analyzed mercury isotopes in fish tissue and streambed sediments collected from 23 streams across a forested-rural to urban-industrial land-use gradient in the Northeastern United States.
In this first regional scale effort, mercury isotope signatures in fish were associated to land-use variables. For example, mercury isotopes in prey and game fish in forested-rural areas were depleted and indicated atmospheric sources of mercury deposited onto the land surface that entered streams through runoff. In comparison, the prey and game fish from urban-industrial areas had enriched signals that indicated legacy sources. These unique isotope signatures were not related to differences in species, diet, habitat, growth, or potential photochemical effects. Isotopic signatures in bottom sediments corresponded to land use but the compositions were different than those in fish collected at the same site indicating that factors controlling mercury accumulation in fish and sediment differ.
Understanding sources of mercury in fish is important because fish are the dominant mercury exposure pathway of methylmercury to humans and to fish-consuming wildlife. This study revealed that mercury isotope measurements in fish tissue provide a tool for distinguishing different sources of mercury that are bioaccumulating into the food web.
The scientists on the USGS Ecologically-Driven Exposure Pathways Science Team are continuing to develop these advanced tools and analytical methods that provide an understanding of health risks associated with mercury exposure. These tools are critical to understanding the effectiveness of mercury-reduction efforts in reducing health risks to humans and other organisms.
This work was supported as part of the Northeast Stream Quality Assessment portion of the National Water-Quality Assessment (NAWQA), the USGS Toxic Substances Hydrology and Contaminant Biology Programs combined, and New York State Energy Research and Development Authority (NYSERDA) contract # 37346.
Below are other science projects associated with this project.
Ecologically-Driven Exposure Pathways Science Team
Science to Help Understand Exposure and Toxicological Effects of Environmental Mercury to Representative Birds
Sublethal Effects of Contaminants in Aquatic Food Webs—Research Challenges and Considerations for Future Studies
Roadmap to Understanding Factors Influencing Mercury Exposure and Adverse Health Effects
New Method Can Measure Naturally Occurring Element Exposure in Hummingbirds Without Harm
Efficacy of Eggshell Analyses as a Nonlethal Method to Estimate Mercury Exposure in Bird Embryos
Synthesis of Mercury Distribution and Bioaccumulation Across Western North America
North American and European Atmospheric Mercury Declines Explained by Local and Regional Emission Reductions
Comprehensive Assessment of Mercury in Streams Explains Major Sources, Cycling, and Effects
Mercury in Fish from 21 National Parks in the West
Complex Response to Decline in Atmospheric Deposition of Mercury
- Overview
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-rural areas indicated atmospheric sources of mercury. In contrast the isotope signatures in fish in urban-industrial areas are indicative of past (legacy) and present local sources.
Sources/Usage: Public Domain.Fish are a source of food for many people in the United States. Mercury in fish tissues is an important issue due to perceived and established health concerns. In streams within the Northeastern United States, mercury levels in fish tissue frequently exceed concentrations associated with toxicity to humans and wildlife. These streams receive mercury in varying proportions from distant atmospheric deposition as well as from local ongoing and legacy point sources, making it difficult to understand the sources of mercury in fish. Without this information it is difficult to link shifts in fish mercury concentrations directly back to changes in mercury source management and mitigation efforts.
U.S. Geological Survey (USGS) scientists provided a tool to differentiate between mercury sources in both sediments and fish using mercury stable isotope analysis. They analyzed mercury isotopes in fish tissue and streambed sediments collected from 23 streams across a forested-rural to urban-industrial land-use gradient in the Northeastern United States.
In this first regional scale effort, mercury isotope signatures in fish were associated to land-use variables. For example, mercury isotopes in prey and game fish in forested-rural areas were depleted and indicated atmospheric sources of mercury deposited onto the land surface that entered streams through runoff. In comparison, the prey and game fish from urban-industrial areas had enriched signals that indicated legacy sources. These unique isotope signatures were not related to differences in species, diet, habitat, growth, or potential photochemical effects. Isotopic signatures in bottom sediments corresponded to land use but the compositions were different than those in fish collected at the same site indicating that factors controlling mercury accumulation in fish and sediment differ.
Understanding sources of mercury in fish is important because fish are the dominant mercury exposure pathway of methylmercury to humans and to fish-consuming wildlife. This study revealed that mercury isotope measurements in fish tissue provide a tool for distinguishing different sources of mercury that are bioaccumulating into the food web.
The scientists on the USGS Ecologically-Driven Exposure Pathways Science Team are continuing to develop these advanced tools and analytical methods that provide an understanding of health risks associated with mercury exposure. These tools are critical to understanding the effectiveness of mercury-reduction efforts in reducing health risks to humans and other organisms.
This work was supported as part of the Northeast Stream Quality Assessment portion of the National Water-Quality Assessment (NAWQA), the USGS Toxic Substances Hydrology and Contaminant Biology Programs combined, and New York State Energy Research and Development Authority (NYSERDA) contract # 37346.
- Science
Below are other science projects associated with this project.
Ecologically-Driven Exposure Pathways Science Team
The Ecologically-Driven Exposure Pathways Integrated Science Team identifies how ecological pathways and physiological processes within a single organism can alter exposure and toxicity of contaminants and pathogens and seek to understand outcomes at different scales from individuals to populations and ecosystems.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...Sublethal Effects of Contaminants in Aquatic Food Webs—Research Challenges and Considerations for Future Studies
U.S. Geological Survey (USGS) and academic scientists partnered to identify challenges and provide considerations for future scientific study designs to advance our understanding of the often subtle sublethal effects of contaminants on individuals, populations, communities, and entire aquatic food webs.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.New Method Can Measure Naturally Occurring Element Exposure in Hummingbirds Without Harm
Seventeen naturally occurring trace elements, including those associated with adverse health impacts when birds are exposed to toxic levels (iron, lead, mercury, selenium, zinc, cadmium, and arsenic) were measured in small birds without harm. The nonlethal method was developed for hummingbirds, with Anna's hummingbirds (Calypte anna) as a test species and can be more broadly applied to other...Efficacy of Eggshell Analyses as a Nonlethal Method to Estimate Mercury Exposure in Bird Embryos
U.S. Geological Survey (USGS) scientists evaluated a nonlethal method to estimate mercury in the embryos of 23 bird species using mercury content in eggshells. This method was effective for a wide range of ages and species.Synthesis of Mercury Distribution and Bioaccumulation Across Western North America
The unique combination of natural processes and human activities present in western North America can strongly affect the exposure of fish and birds to methylmercury, the most toxic form of mercury (Hg).North American and European Atmospheric Mercury Declines Explained by Local and Regional Emission Reductions
Recent findings from a consortium of university, State, and U.S. Geological Survey (USGS) scientists indicate that declining atmospheric concentrations of mercury (Hg) can be explained by the phaseout of mercury in many commercial products and by reduced emissions from utilities over the past two decades.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...Mercury in Fish from 21 National Parks in the West
U.S. Geological Survey (USGS) and National Park Service (NPS) scientists collaborated in the first study to measure mercury in fish from remote places in 21 National Parks spanning 10 Western States, including Alaska. Mercury levels in fish generally were low, but were elevated in some local areas, including two parks in Utah and Alaska where samples taken from sport fish exceeded the U.S...Complex Response to Decline in Atmospheric Deposition of Mercury
U.S. Geological Survey (USGS) scientists found that mercury concentrations in shallow waters and methylmercury (MeHg) concentrations in fish in four lakes in Voyageurs National Park, Minnesota, were not consistent with decreases in the wet atmospheric deposition of mercury recorded at nearby monitoring stations for over a decade. Methylmercury is a toxic form of mercury (Hg) that accumulates and... - Publications
- News