Karen R Murray, Ph.D.
Intro
I am currently a Research Scientist Emeritus with the U.S. Geological Survey (USGS). I began working with USGS as an aquatic ecologist in 1991 and retired as a research ecologist in May 2020. As a Scientist Emeritus, I continue my work on selected projects in a volunteer capacity. My major research focus has been on mercury cycling and bioaccumulation in aquatic ecosystems, especially streams and rivers. I have also investigated the effects of urbanization, forest fragmentation, and hydrologic alteration on stream ecosystems. Much of my work has involved the integration of biological aspects (e.g. food web dynamics, community ecology) into multi-disciplinary studies. I have a Ph.D. in environmental biology from the State University of New York College of Environmental Science and Forestry in Syracuse, and a B.A. in environmental studies from Northland College in Ashland, Wisconsin. In addition to my volunteer work with USGS, I volunteer as the Water Quality Monitoring Coordinator for the Lake Onota Preservation Association (LOPA), and am a member of LOPA's Board of Directors.
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An empirical approach to modeling methylmercury concentrations in an Adirondack stream watershed
Optimizing stream water mercury sampling for calculation of fish bioaccumulation factors
Influence of dietary carbon on mercury bioaccumulation in streams of the Adirondack Mountains of New York and the Coastal Plain of South Carolina, USA
Fluvial transport of mercury, organic carbon, suspended sediment, and selected major ions in contrasting stream basins in South Carolina and New York, October 2004 to September 2009
Intra- and inter-basin mercury comparisons: Importance of basin scale and time-weighted methylmercury estimates
Mercury bioaccumulation studies in the National Water-Quality Assessment Program--biological data from New York and South Carolina, 2005-2009
Shallow groundwater mercury supply in a coastal plain stream
Landscape controls on total and methyl Hg in the Upper Hudson River basin, New York, USA
Spatial patterns of mercury in macroinvertebrates and fishes from streams of contrasting forested landscapes in the eastern United States
Spatial and seasonal variability of dissolved methylmercury in two stream basins in the Eastern United States
Environmental settings of streams sampled for mercury in New York and South Carolina, 2005-09
Landscape characteristics affecting streams in urbanizing regions of the Delaware River Basin (New Jersey, New York, and Pennsylvania, U.S.)
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An empirical approach to modeling methylmercury concentrations in an Adirondack stream watershed
Inverse empirical models can inform and improve more complex process-based models by quantifying the principal factors that control water quality variation. Here we developed a multiple regression model that explains 81% of the variation in filtered methylmercury (FMeHg) concentrations in Fishing Brook, a fourth-order stream in the Adirondack Mountains, New York, a known “hot spot” of Hg bioaccumuAuthorsDouglas A. Burns, Elizabeth A. Nystrom, David M. Wolock, Paul M. Bradley, Karen Riva-MurrayOptimizing stream water mercury sampling for calculation of fish bioaccumulation factors
Mercury (Hg) bioaccumulation factors (BAFs) for game fishes are widely employed for monitoring, assessment, and regulatory purposes. Mercury BAFs are calculated as the fish Hg concentration (Hgfish) divided by the water Hg concentration (Hgwater) and, consequently, are sensitive to sampling and analysis artifacts for fish and water. We evaluated the influence of water sample timing, filtration, anAuthorsKaren Riva-Murray, Paul M. Bradley, Celeste A. Journey, Mark E. Brigham, Barbara C. Scudder Eikenberry, Christopher Knightes, Daniel T. ButtonInfluence of dietary carbon on mercury bioaccumulation in streams of the Adirondack Mountains of New York and the Coastal Plain of South Carolina, USA
We studied lower food webs in streams of two mercury-sensitive regions to determine whether variations in consumer foraging strategy and resultant dietary carbon signatures accounted for observed within-site and among-site variations in consumer mercury concentration. We collected macroinvertebrates (primary consumers and predators) and selected forage fishes from three sites in the Adirondack MouAuthorsKaren Riva-Murray, Paul M. Bradley, Lia C. Chasar, Daniel T. Button, Mark E. Brigham, Barbara C. Scudder Eikenberry, Celeste A. Journey, Michelle A. LutzFluvial transport of mercury, organic carbon, suspended sediment, and selected major ions in contrasting stream basins in South Carolina and New York, October 2004 to September 2009
A spatially extensive assessment of the environmental controls on mercury transport and bioaccumulation in stream ecosystems in New York and South Carolina was conducted as part of the U.S. Geological Survey National Water-Quality Assessment Program and included the determination of fluvial transport of mercury and associated constituents during water years 2005–2009. (A water year extends from OcAuthorsCeleste A. Journey, Douglas A. Burns, Karen Riva-Murray, Mark E. Brigham, Daniel T. Button, Toby D. Feaster, Matthew D. Petkewich, Paul M. BradleyIntra- and inter-basin mercury comparisons: Importance of basin scale and time-weighted methylmercury estimates
To assess inter-comparability of fluvial mercury (Hg) observations at substantially different scales, Hg concentrations, yields, and bivariate-relations were evaluated at nested-basin locations in the Edisto River, South Carolina and Hudson River, New York. Differences between scales were observed for filtered methylmercury (FMeHg) in the Edisto (attributed to wetland coverage differences) but notAuthorsPaul M. Bradley, Celeste A. Journey, Mark E. Bringham, Douglas A. Burns, Daniel T. Button, Karen Riva-MurrayMercury bioaccumulation studies in the National Water-Quality Assessment Program--biological data from New York and South Carolina, 2005-2009
The U.S. Geological Survey National Water-Quality Assessment Program conducted a multidisciplinary study from 2005–09 to investigate the bioaccumulation of mercury in streams from two contrasting environmental settings. Study areas were located in the central Adirondack Mountains region of New York and the Inner Coastal Plain of South Carolina. Fish, macroinvertebrates, periphyton (attached algaeAuthorsKaren M. Beaulieu, Daniel T. Button, Barbara C. Scudder Eikenberry, Karen Riva-Murray, Lia C. Chasar, Paul M. Bradley, Douglas A. BurnsShallow groundwater mercury supply in a coastal plain stream
Fluvial methylmercury (MeHg) is attributed to methylation in up-gradient wetland areas. This hypothesis depends on efficient wetland-to-stream hydraulic transport under nonflood and flood conditions. Fluxes of water and dissolved (filtered) mercury (Hg) species (FMeHg and total Hg (FTHg)) were quantified in April and July of 2009 in a reach at McTier Creek, South Carolina to determine the relativeAuthorsPaul M. Bradley, Celeste A. Journey, Mark A. Lowery, Mark E. Brigham, Douglas A. Burns, Daniel T. Button, Francis H. Chapelle, Michelle A. Lutz, Mark C. Marvin-DiPasquale, Karen Riva-MurrayLandscape controls on total and methyl Hg in the Upper Hudson River basin, New York, USA
Approaches are needed to better predict spatial variation in riverine Hg concentrations across heterogeneous landscapes that include mountains, wetlands, and open waters. We applied multivariate linear regression to determine the landscape factors and chemical variables that best account for the spatial variation of total Hg (THg) and methyl Hg (MeHg) concentrations in 27 sub-basins across the 493AuthorsDouglas A. Burns, K. Riva-Murray, P. M. Bradley, G. R. Aiken, M. E. BrighamSpatial patterns of mercury in macroinvertebrates and fishes from streams of contrasting forested landscapes in the eastern United States
Controls on mercury bioaccumulation in lotic ecosystems are not well understood. During 2007–2009, we studied mercury and stable isotope spatial patterns of macroinvertebrates and fishes from two medium-sized (AuthorsKaren Riva-Murray, Lia C. Chasar, Paul M. Bradley, Douglas A. Burns, Mark E. Brigham, Martyn J. Smith, Thomas A. AbrahamsenSpatial and seasonal variability of dissolved methylmercury in two stream basins in the Eastern United States
We assessed methylmercury (MeHg) concentrations across multiple ecological scales in the Edisto (South Carolina) and Upper Hudson (New York) River basins. Out-of-channel wetland/floodplain environments were primary sources of filtered MeHg (F-MeHg) to the stream habitat in both systems. Shallow, open-water areas in both basins exhibited low F-MeHg concentrations and decreasing F-MeHg mass flux. DoAuthorsPaul M. Bradley, Douglas A. Burns, Karen Riva-Murray, Mark E. Brigham, Daniel T. Button, Lia C. Chasar, Mark Marvin-DiPasquale, Mark A. Lowery, Celeste A. JourneyEnvironmental settings of streams sampled for mercury in New York and South Carolina, 2005-09
This report summarizes the environmental settings of streams in New York and South Carolina, where the U.S. Geological Survey completed detailed investigations during 2005-09 into factors contributing to mercury bioaccumulation in top-predator fish and other stream organisms. Descriptions of location, land use/land cover, climate, precipitation, atmospheric deposition, hydrology, water temperatureAuthorsBarbara C. Scudder Eikenberry, Karen Riva-Murray, Martyn J. Smith, Paul M. Bradley, Daniel T. Button, Jimmy M. Clark, Douglas A. Burns, Celeste A. JourneyLandscape characteristics affecting streams in urbanizing regions of the Delaware River Basin (New Jersey, New York, and Pennsylvania, U.S.)
Widespread and increasing urbanization has resulted in the need to assess, monitor, and understand its effects on stream water quality. Identifying relations between stream ecological condition and urban intensity indicators such as impervious surface provides important, but insufficient information to effectively address planning and management needs in such areas. In this study we investigate thAuthorsK. Riva-Murray, R. Riemann, P. Murdoch, J.M. Fischer, R. Brightbill