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Thomas A. Abrahamsen

Publications and source records attributed to Thomas A. Abrahamsen.

9 recordsLinked to original sources
USGS2011

Spatial 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&ndash;2009, we studied mercury and stable isotope spatial patterns of macroinvertebrates and fishes from two medium-sized (<80 km 2 ) forested basins in contrasting settings. Samples were collected seasonally from multiple sites across the Fishing Brook basin (FBNY), in New York's Adirondack Mountains, and the McTier Creek basin (MCSC), in South Carolina's Coastal Plain. Mean methylmercury (MeHg) concentrations within macroinvertebrate feeding groups, and mean total mercury (THg) concentrations within most fish feeding groups were similar between the two regions. However, mean THg concentrations in game fish and forage fish, overall, were much lower in FBNY (1300 and 590 ng/g dw, respectively) than in MCSC (2300 and 780 ng/g dw, respectively), due to lower trophic positions of these groups from FBNY (means 3.3 and 2.7, respectively) than MCSC (means 3.7 and 3.3, respectively). Much larger spatial variation in topography and water chemistry across FBNY contributed to greater spatial variation in biotic Hg and positive correlations with dissolved MeHg and organic carbon in streamwater. Hydrologic transport distance (HTD) was negatively correlated with biotic Hg across FBNY, and was a better predictor than wetland density. The small range of landscape conditions across MCSC resulted in no consistent spatial patterns, and no discernable correspondence with local-scale environmental factors. This study demonstrates the importance of local-scale environmental factors to mercury bioaccumulation in topographically heterogeneous landscapes, and provides evidence that food-chain length can be an important predictor of broad-scale differences in Hg bioaccumulation among streams.

New York, South Carolina↗
USGS2011

Trace element, semivolatile organic, and chlorinated organic compound concentrations in bed sediments of selected streams at Fort Gordon, Georgia, February-April 2010

A spatial survey of streams was conducted from February to April 2010 to assess the concentrations of major ions, selected trace elements, semivolatile organic compounds, organochlorine pesticides, and polychlorinated biphenyls associated with the bed sediments of surface waters at Fort Gordon military installation near Augusta, Georgia. This investigation expanded a previous study conducted in May 1998 by the U.S. Geological Survey, in cooperation with the U.S. Department of the Army Environmental and Natural Resources Management Office of the U.S. Army Signal Center and Fort Gordon, that evaluated the streambed sediment quality of selected surface waters at Fort Gordon. The data presented in this report are intended to help evaluate bed sediment quality in relation to guidelines for the protection of aquatic life, and identify temporal trends in trace elements and semivolatile organic compound concentrations at streambed sites previously sampled. Concentrations of 34 major ions and trace elements and 102 semivolatile organic, organochlorine pesticide, and polychlorinated biphenyl compounds were determined in the fine-grained fraction of bed sediment samples collected from 13 of the original 29 sites in the previous study, and 22 additional sites at Fort Gordon. Three of the sites were considered reference sites as they were presumed to be located away from potential sources of contaminants and were selected to represent surface waters flowing onto the fort, and the remaining 32 nonreference sites were presumed to be located within the contamination area at the fort. Temporal trends in trace elements and semivolatile organic compound concentrations also were evaluated at 13 of the 32 nonreference sites to provide an assessment of the variability in the number of detections and concentrations of constituents in bed sediment associated with potential sources, accumulation, and attenuation processes. Major ion and trace element concentrations in fine-grained bed sediment samples from most nonreference sites exceeded concentrations in samples from reference sites at Fort Gordon. Bed sediments from one of the nonreference sites sampled contained the highest concentrations of copper and lead with elevated levels of zinc and chromium relative to reference sites. The percentage change of major ions, trace elements, and total organic carbon that had been detected at sites previously sampled in May 1998 and current bed sediment sites ranged from -4 to 8 percent with an average percentage change of less than 1 percent. Concentrations of major ions and trace elements in bed sediments exceeded probable effect levels for aquatic life (based on the amphipod Hyalella azteca) established by the U.S. Environmental Protection Agency at 46 and 69 percent of the current and previously sampled locations, respectively. The greatest frequency of exceedances for major ions and trace elements in bed sediments was observed for lead. Concentrations of semivolatile organic compounds, organochlorine pesticides, and polychlorinated biphenyls were detected in bed sediment samples at 94 percent of the sites currently sampled. Detections of these organic compounds were reported with greater frequency in bed sediments at upstream sampling locations, when compared to downstream locations. The greatest number of detections of these compounds was reported for bed sediment samples collected from two creeks above a lake. The percentage change of semivolatile organic compounds detected at previously sampled and current bed sediment sites ranged from -68 to 100 percent with the greatest percentage increase reported for one of the creeks above the lake. Concentrations of semivolatile organic compounds and polychlorinated biphenyls in bed sediments exceeded aquatic life criteria established by the U.S. Environmental Protection Agency at three sites. Contaminant compounds exceeding aquatic life criteria included fluoranthene, phenanthrene, anthracene, benzo(a)anthracene

Georgia↗
USGS2008

Limnological Conditions in Lake William C. Bowen and Municipal Reservoir #1, Spartanburg County, South Carolina, August to September 2005, May 2006, and October 2006

The U.S. Geological Survey, in cooperation with the Spartanburg Water System, conducted three spatial surveys of the limnological conditions in Lake William C. Bowen (Lake Bowen) and Municipal Reservoir #1 (Reservoir #1), Spartanburg County, South Carolina, during August to September 2005, May 2006, and October 2006. The surveys were conducted to identify spatial distribution and concentrations of geosmin and 2-methylisoborneol, common trophic state indicators (nutrients, transparency, and chlorophyll a), algal community structure, and stratification of the water column at the time of sampling. Screening tools such as the Carlson trophic state index, total nitrogen to total phosphorus ratios, and relative thermal resistance to mixing were used to help compare data among sites and among seasons. Water-column samples were collected at two depths at each selected site: a near-surface sample collected above a 1-meter depth and a lake-bottom sample collected at a depth of 2.5 to 7 meters, depending on the depth at the site. The degree of stratification of the water column was demonstrated by temperature-depth profiles and computed relative thermal resistance to mixing. Seasonal occurrence of thermal stratification (August to September 2005; May 2006) and de-stratification (October 2006) was evident in the depth profiles of water temperature in Lake Bowen. The most stable water-column (highest relative thermal resistance to mixing) conditions occurred in Lake Bowen during the August to September 2005 survey. The least stable water-column (destratified) conditions occurred in Lake Bowen during the October 2006 survey and Reservoir #1 during all three surveys. Changes with depth in dissolved oxygen (decreased with depth to near anoxic conditions in the hypolimnion), pH (decreased with depth), and specific conductance (increased with depth) along with thermal stratification indicated Lake Bowen was exhibiting characteristics common to both mesotrophic and eutrophic conditions. Nutrient dynamics were different in Lake Bowen during the May 2006 survey from those during the August to September 2005 and October 2006 surveys. Total organic nitrogen concentrations (total Kjeldahl nitrogen minus ammonia) remained relatively constant within the surveys and ranged from 0.15 to 0.36 milligram per liter during the period of study. Nitrate was the dominant inorganic species of nitrogen during May 2006. Ammonia was the dominant species during the August to September 2005 and October 2006 surveys. During the August and September 2005 survey, ammonia was detected only in bottom samples collected in the near anoxic hypolimnion, but during the October 2006 survey, ammonia was detected under destratified conditions in surface and bottom samples. In Lake Bowen, total phosphorus concentrations in bottom samples did not exhibit the dramatic, high values during the May 2006 and October 2006 surveys (0.009 to 0.014 milligram per liter) that were identified for the August to September 2005 survey (0.022 to 0.034 milligram per liter). Chlorophyll a concentrations appeared to vary with the species of inorganic nitrogen. Greater chlorophyll a concentrations were identified in samples from the May 2006 survey (6.8 to 15 micrograms per liter) than in the August to September 2005 (1.2 to 6.4 micrograms per liter) and October surveys (5.6 to 8.2 micrograms per liter) at all sites in Lake Bowen and Reservoir #1. For the three limnological surveys, surface concentrations of chlorophyll a and total phosphorus were well below established numerical criteria for South Carolina. In general, the computed trophic state indices indicated that mesotrophic conditions were present in Lake Bowen and Reservoir #1. The total nitrogen to total phosphorus ratios in Lake Bowen and Reservoir #1 were below 22:1 for the August to September 2005 survey, indicating a high probability of dominance by nitrogen-fixing cyanobacteria. Ratios during the May and October 2006 surveys at

South Carolina↗
USGS2001

Ecological data collected in the Santee River basin and coastal drainages, North and South Carolina, 1996–98

As part of the National Water-Quality Assessment Program, ecological investigations were conducted in 23 reaches of 16 streams in the Santee River Basin and Coastal Drainages study unit in North and South Carolina during 1996-98. Habitat characteristics, such as stream width and depth, bank composition, bank vegetative cover, stream shading by overhanging vegetation, and streambed composition were recorded. Algal and benthic invertebrate communities were sampled using quantitative and qualitative techniques. These data will provide information needed to: (1) support findings of the effects of human landuse activities on water quality by augmenting or enhancing physical and chemical water-quality data, (2) provide a basic overview of aquatic community structure in selected stream reaches in the study unit, and (3) provide a means for comparing aquatic communities in subsequent years of the assessment program.

North Carolina, South Carolina↗
USGS2000

Water quality in the Santee River basin and coastal drainages, North and South Carolina, 1995-98

Surface water sampled in the Santee River basin and coastal drainages generally meets existing Federal and State guidelines for drinking-water quality and protection of aquatic life. However, urban and agricultural land uses have affected water quality, as indicated by elevated concentrations of bacteria, pesticides, and nutrients in basins dominated by these land uses.

North Carolina, South Carolina↗