Rebecca J. Currie

An integrative assessment of a watershed impacted by abandoned mined land discharges.

The Ely Creek watershed in Lee County, VA, USA, contains an abundance of abandoned mined land areas with acid mine drainage (AMD) that contaminate the majority of the creek and its confluence into Stone Creek. Acidic pH measurements ranged from 2.73 to 5.2 at several stations throughout the watershed. Sediments had high concentrations of iron (approximately 10,000 mg kg-1), aluminum (approximately 1,500 mg kg-1), magnesium (approximately 400 mg kg-1) and manganese (approximately 150 mg kg-1), and habitat was partially to non-supporting at half of the stations due to sedimentation. Benthic macroinvertebrate surveys at six of 20 stations sampled in the watershed yielded no macroinvertebrates, while eight others had total abundances of only one to nine organisms. Four reference stations contained > or = 100 organisms and at least 13 different taxa. Asian clam in situ toxicity testing supported field survey results. Laboratory, 10-day survival/impairment sediments tests with Daphnia magna and Chironomus tentans and 48-h water column bioassays with Ceriodaphnia dubia indicated environmental stress to a lesser degree. Ten parameters that were directly influenced by AMD through physical, chemical, ecological and toxicological endpoints were assimilated into an ecotoxicological rating (ETR) to form a score of 0-100 points for the 20 sampling stations, and the lower the score the greater the AMD stress. Twelve of the 15 sampling stations influenced by AMD received an ETR score of 13.75-57.5, which were categorized as severely stressed (i.e. comprised the < 60 percentile category) and worthy of the highest priority for future ecological restoration activities in the watershed.

Cold Tolerance and Potential Overwintering of the Red-Bellied Piranha Pygocentrus nattereri in the United States

Abstract Red-bellied piranhas Pygocentrus nattereri (also known as red piranhas) acclimated to 15–35°C had critical thermal minima (± SD) from 10.5 ± 0.31°C to 19.7 ± 1.25°C. The chronic thermal minimum (± SD) based on equilibrium loss of fish exposed to decreasing water temperatures of 1°C/d was 10.0 ± 0.15°C. Acclimation temperature incorporated into a second-order polynomial regression model accounted for 97% of variation in critical thermal minima. Fish in the laboratory were unable to capture live goldfish Carassius auratus at temperatures less than 14°C but accepted frozen adult brine shrimp Artemia sp. attemperatures as low as 12°C. When combined with shallow surface water temperature estimates for January, our temperature tolerance and feeding behavior data suggested that red-bellied piranhas may overwinter in nine southern states of the USA with varying degrees of success. Red-bellied piranhas would not overwinter where temperatures fall below 10°C. These fish could overwinter at temperatures of ...

Upper and Lower Temperature Tolerances of Juvenile Freshwater Game-Fish Species Exposed to 32 days of Cycling Temperatures

Temperature tolerance quantified as CTminima and CTmaxima of channel catfish (Ictalurus punctatus), largemouth bass (Micropterus salmoides) and rainbow trout (Oncorhynchus mykiss) periodically measured during 32 days of exposure to a 10 °C diel thermoperiod were compared to those determined at constant acclimation temperatures equal to the minimum, midpoint and maximum of each species’ thermoperiod. The diel thermoperiod for channel catfish and largemouth bass extended from 20 to 30 °C while rainbow trout were cycled between 10 and 20 °C. A hypothesis that the zone of temperature tolerance would be enlarged during exposure to a 10 °C thermoperiod was tested. Mean CTmaxima and CTminima during cycling ranged from 38.5 to 39.6 °C and 6.1 to 6.6 °C (channel catfish), 35.6 to 37.3 °C and 5.9 to 7.7 °C (largemouth bass) and 27.3 to 29.3 °C and 0.1 to 1.4 °C (rainbow trout). Our data indicate that with one exception both upper and lower temperature tolerance for each of these three species exposed to the diel temperature cycle were more similar to those of fish acclimated to a constant temperature near the midpoint of the thermoperiod than to either the minimum or maximum temperature of the cycle. The exception occurred in rainbow trout where the mean CTmaximum during cycling was equivalent to an acclimation temperature midway between the mean and peak acclimation temperature. Furthermore, in all three species the temperature tolerance scope (CTmaximum − CTminimum) was less in fish exposed to the thermoperiod used in this research. The temperature tolerance ability of any of the three test species was not enhanced.

Influence of conductivity dissipation on benthic macroinvertebrates in the North Fork Holston River, Virginia downstream of a point source brine discharge during severe low-flow conditions.

ABSTRACT The North Fork Holston River (NFHR) was examined in fall 2005 to determine the potential impact of a brine discharge on benthic macroinvertebrates. Conductivity of the discharge ranged from 5900 to 10,930 μ S/cm with a highest measurement of 18,000 μ S/cm. During normal flow, conductivity dissipates rapidly downstream of the discharge; however, low-flow conditions in 2005 hindered dissipation. Benthic macroinvertebrate surveys determined statistically significant differences (p = .05) in all metrices between sites excluding taxa richness. Hydropsychid caddisflies were the predominant taxa at the first two sites below the brine discharge, accounting for 74.3 and 68.8% of the organisms collected. Therefore, Ephemeroptera-Plecoptera-Trichoptera (EPT) abundance minus Hydropsychidae [EPT-H] was the most predictive parameter measured. When hydropsychids were removed from statistical analyses, mean EPT abundance was highest at upstream reference sites 1 and 2 (256 and 297, respectively) and reduced at all downstream sites, ranging from 24 to 52 EPT organisms. Virginia Stream Condition Index (SCI) scores indicated impairment downstream of the discharge with scores of 46.9, 41.8, and 55.8, well below the impairment threshold of 61. These results suggest subchronic, intermittent toxicity occurs under low-flow and may contribute to altered benthic macroinvertebrate assemblages downstream of the brine discharge for approximately 26 miles.

Comparison of Asian clam field bioassays and benthic community surveys in quantifying effects of a coal-fired power plant effluent on Clinch River biota

Survival and growth of Asian clamsmay be more sensitive endpoints than benthicmacroinvertebrate community richness parametersat distinguishing biotic impairmentattributable to complex effluents fromcoal-burning utilities. We conducted (1) fieldbioassays with the Asian clam (Corbiculafluminea) during 2000–02 and (2) rapidbioassessments of benthic macroinvertebratecommunities during 2000–01 at sitesupstream/downstream of American ElectricPowers (AEP) Clinch River Plant (CRP) inRussell County, Virginia (U.S.A). Survival andgrowth of transplanted C. fluminea weresignificantly impaired within the CRP effluentplume (averages of 35% and 0.21 mm,respectively) relative to all other study siteswithin the Clinch River (averages of 89% and1.58 mm). Conversely, richness metrics forEphemeroptera,Ephemeroptera-Plecoptera-Trichoptera (EPT), andtotal taxa were not reduced downstream of theCRP. However, relative abundance metrics forEphemeroptera and EPT were minimally reduced atthe CRP-influenced site during 2000–01. Moreimportantly, our results suggest that richnessmetrics for benthic macroinvertebratecommunities may be inadequate for assessing theeffects of complex industrial effluents on C. fluminea. These findings have implicationsfor bioassessment techniques employed tomonitor streams inhabited by imperiledfreshwater mussels because (1) C. flumineaand Unionoidea are ecologicallysimilar and (2) recent findings suggest certaingenera of Unionidae may be more sensitive thanC. fluminea.

An Investigation of Total Mercury in Sediments and Interstitial Water in the North Fork Holston River below Saltville, Virginia, USA

ABSTRACT The North Fork Holston River (NFHR) is historically renowned for having one of the most diversity rich unionid populations (Unionidae) worldwide; however, in recent decades, drastic reductions in mussel diversity, abundance, and recruitment have been documented. Unionid declines have been blamed on anthropogenic influences, specifically mercury-contaminated wastewater from a now closed chlorine-alkali plant in Saltville, VA. The objective of this research was to evaluate total mercury (Hg) contamination of sediments and interstitial waters in the NFHR beginning below Saltville and downstream for approximately 50 river miles. Mercury contaminated sediments and interstitial water were found downstream of the closed plant with the highest sediment concentration of 2.82 mg/kg dry weight total Hg found at river mile (rm) 80 and the highest interstitial water value at rm 30.4 with 2.1 μg/l. After 60-d in situ testing, total Hg concentrations in Asian clam (Corbicula fluminea) tissues were found to range from 0.016 to 0.13 mg/kg, while resident clams had Hg concentrations of 0.094 and 0.11 mg/kg wet weight. Although chronic toxicity was not observed, based on Corbicula growth and survival tests, nor in testing with cladocerans, mercury contamination is still a persistent problem at sites in the NFHR below the closed plant with negative correlations between mean clam growth and sediment Hg concentrations.

Measures of Hydrology, Habitat, Toxicity, and Biodiversity

The role of quantitative measures of hydrology and hydraulic watershed properties and their impact on ecological risk assessment was investigated. Pearson correlation coefficients were examined between metrics of ecotoxicology and physically based parameters describing channel, velocity, and flow conditions at each test site. A total of 83 single value ecological endpoints at each site were used. Measures of benthic macroinvertebrate biodiversity, biological habitat condition, sediment toxicity, and in-situ clam toxicity were found to be weakly to moderately correlated with channel geomorphology, flow, and velocity field parameters. For each endpoint, between 30 and 54 test sites were surveyed. For watershed areas impacted by abandoned surface coal mines, in-situ clam toxicity testing using Corbicula fluminea was found to be the most sensitive biological indicator of stress. Concurrently, 25 of 37 hydraulic condition endpoints examined also resulted in the greatest correlation observed with clam toxicity among all endpoints (R2 = 0.2 - 0.62, R >0 unless noted). Novel application of a relative standard penetration test used to evaluate sediment depth instream was found to be the strongest factor related to in-lab 10-day static sediment toxicity survivorship results for the midge Chironomus tentans (R2 = 0.53). Aerial extent of AML and sediment depth were the strongest factors related to macroinvertebrate total taxa (R2 = 0.28) while bankfull width to depth ratio gave the strongest correlation to total abundance (R2 = 0.59). Results indicate the potential to better quantify hydrology and hydraulic aspects of ecology by augmenting existing “rapid bioassessment habitat” protocols with a select set of quantitative measurements.