David J. Soucek

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.

Effects of hardness, chloride, and acclimation on the acute toxicity of sulfate to freshwater invertebrates

The acute toxicity of sulfate to Ceriodaphnia dubia, Chironomus tentans, Hyalella azteca, and Sphaerium simile was assessed to support potential updates of Illinois (USA) sulfate criteria for the protection of aquatic life. The mean lethal concentrations to 50% of a sample population (LC50s), expressed as mg S04(-2)/L, in moderately hard reconstituted water (MHRW) were as follows: 512 mg/L for H. azteca, 2,050 mg/L for C. dubia, 2,078 mg/L for S. simile, and 14,134 mg/L for C. tentans. At constant sulfate (approximately 2,800 mg/L) and hardness (106 mg/L), survival of H. azteca was positively correlated with chloride concentration. Hardness also was found to ameliorate sodium sulfate toxicity to C. dubia and H. azteca, with LC50s for C. dubia increasing from 2,050 mg SO4(-2)/L at hardness = 90 mg/L to 3,516 mg SO4(-2)/L at hardness = 484 mg/L. Using a reformulated MHRW with a similar hardness but higher chloride concentration and different calcium to magnesium ratio than that in standard MHRW, the mean LC50 for H. azteca increased to 2,855 mg/L, and the LC50 for C. dubia increased to 2,526 mg/L. Acclimation of C. dubia to 500 and 1,000 mg SO4(-2)/L for several generations nominally increased mean LC50 values compared with those cultured in standard MHRW.

Comparison of hardness- and chloride-regulated acute effects of sodium sulfate on two freshwater crustaceans.

Based on previous observations that hardness (and potentially chloride) influences sodium sulfate toxicity, the objective of the current study was to quantify the influence of both chloride and water hardness on acute toxicity to Hyalella azteca and Ceriodaphnia dubia. In addition, observed toxicity data from the present study were compared to toxicity predictions by the salinity/ toxicity relationship (STR) model. Hardness had a strong influence on sulfate toxicity that was similar for both crustaceans, and nearly identical median lethal concentration (LC50)/hardness slopes were observed for the two species over the tested range. Chloride had a strong but variable influence on sulfate acute toxicity, depending on the species tested and the concentration range. At lower chloride concentrations, LC50s for H. azteca strongly were correlated positively with chloride concentration, although chloride did not affect the toxicity of sodium sulfate to C. dubia. The opposite trend was observed over the higher range of chloride concentrations where there was a negative correlation between chloride concentration and sulfate LC50 for both species. The widely ranging values for both species and a high correlation between LC50s in terms of sulfate and conductivity suggested that, whether based on sulfate, conductivity, or total dissolved solids (TDS), attempts at water quality standard development should incorporate the fact that water quality parameters such as hardness and chloride strongly influence the toxicity of high TDS solutions. The STR model predicted toxicity to C. dubia relatively well when chloride was variable and hardness fixed at approximately 100 mg/L; however, the model did not account for the protective effect of hardness on major ion/TDS toxicity.

Influence of water hardness and sulfate on the acute toxicity of chloride to sensitive freshwater invertebrates

Total dissolved solids (TDS) represent the sum of all common ions (e.g., Na, K, Ca, Mg, chloride, sulfate, and bicarbonate) in freshwater. Currently, no federal water quality criteria exist for the protection of aquatic life for TDS, but because the constituents that constitute TDS are variable, the development of aquatic life criteria for specific ions is more practical than development of aquatic life criteria for TDS. Chloride is one such ion for which aquatic life criteria exist; however, the current aquatic life criteria dataset for chloride is more than 20 years old. Therefore, additional toxicity tests were conducted in the current study to confirm the acute toxicity of chloride to several potentially sensitive invertebrates: water flea (Ceriodaphnia dubia), fingernail clams (Sphaerium simile and Musculium transversum), snail (Gyraulus parvus), and worm (Tubifex tubifex), and determine the extent to which hardness and sulfate modify chloride toxicity. The results indicated a significant ameliorating effect of water hardness (calcium and magnesium) on chloride toxicity for all species tested except the snail; for example, the 48-h chloride median lethal concentration (LC50) for C. dubia at 50 mg/L hardness (977 mg Cl(-) /L) was half that at 800 mg/L hardness (1,836 mg Cl(-) /L). Conversely, sulfate over the range of 25 to 600 mg/L exerted a negligible effect on chloride toxicity to C. dubia. Rank order of LC50 values for chloride at a given water hardness was in the order (lowest to highest): S. simile < C. dubia < M. transversum < G. parvus < T. tubifex. Results of the current study support the contention that the specific conductivity or TDS concentration of a water body alone is not a sufficient predictor of acute toxicity and that knowledge of the specific ion composition is critical.

Site-Specific Derivation of the Acute Copper Criteria for the Clinch River, Virginia

Previous studies indicated that inputs from the Clinch River Plant (CRP), a coal-burning, power-generating facility in Carbo, Virginia, caused impairment to transplanted freshwater mussels. These findings necessitated the examination of instream biological responses to CRP effluents. Therefore, our objective was to derive a site-specific Criterion Maximum Concentration (CMC) for copper (Cu), the toxic constituent of the effluent. This was accomplished by conducting acute toxicity tests with Cu using 17 different genera native to or currently residing in the Clinch River watershed. Four native unionids and a mayfly (Isonychia bicolor) had genus mean acute values of 60 µJ.g/L or lower (ranging from 37 to 60 µJ,g/L). With a GMAV of 88 µJ,g/L, Ceriodaphnia dubia ranked sixth among the 17 genera tested, and the fathead minnow, Pimephales promelas, ranked fourteenth with a GMAV of 310 µJ.g/L. Despite the sensitivity of the indigenous mussels tested, the site-specific CMC of 18 µJg/L was not substantially lower than the national CMC for Cu (20 µJ,g/L, hardness = 150 mg/L as CaCO3). While we conducted acute exposure tests, future investigations should incorporate both biomarker and population or community-level studies to determine low-level contaminant impacts on freshwater mussels.

The common ecotoxicology laboratory strain of Hyalella azteca is genetically distinct from most wild strains sampled in eastern North America.

The amphipod Hyalella azteca is commonly used as a model for determining safe concentrations of contaminants in freshwaters. The authors sequenced the mitochondrial cytochrome c oxidase subunit I (COI) gene for representatives of 38 populations of this species complex from US and Canadian toxicology research laboratories and eastern North American field sites to determine their genetic relationships. With 1 exception, all US and Canadian laboratory cultures sampled were identified as conspecific. In 22 wild populations spanning 5 US states and 1 Canadian province, the commonly occurring laboratory species was found only in northern Florida, USA. Therefore, the diversity of the H. azteca species complex detected in the wild is not accurately represented in North American laboratories, questioning the reliability of H. azteca cultures currently in use to accurately predict the responses of wild populations in ecotoxicological assays. The authors also examined the utility of different COI nucleotide fragments presently in use to determine phylogenetic relationships in this group and concluded that saturation in DNA sequences leads to inconsistent relationships between clades. Amino acid sequences for COI were not saturated and may allow a more accurate phylogeny estimate. Hyalella azteca is crucial for developing water-quality regulations; therefore, laboratories should know and standardize the strain(s) they use to confidently compare toxicity tests across laboratories and determine whether they are an appropriate surrogate for their regions.

Re-examining the Importance of Fish in the Diets of Stream-dwelling Crayfishes: Implications for Food Web Analyses and Conservation

Abstract We examined the diets of two species of stream-dwelling North American crayfishes (Orconectes propinquus and O. rusticus) at eight sites in the Midwestern United States both by measuring natural abundances of stable isotopes of carbon and nitrogen and by quantifying gut contents. Our goals were to test the hypothesis proposed by others that crayfish are primarily carnivorous, and in particular, to examine the frequency of fish consumption by crayfishes. Stable isotope profiles indicated that both species of crayfish were omnivorous and had a trophic position between those of other invertebrate consumers and fishes. Isotope profiles demonstrated that lower quality foods such as leaf litter, periphyton and fine particulate organic matter made up a larger proportion of the diets of both species than did animal material and that fish comprised approximately 12% of the diet of both crayfishes; this percentage was less variable than that of other food types. Gut content analysis corroborated stable isotope results in finding a similar percent occurrence of fish matter in both species. Our results suggest that the consumption of fish by crayfishes is often underestimated or ignored.

Isolating effects of total dissolved solids on aquatic life in central appalachian coalfield streams

Elevated levels of total dissolved solids (TDS) have been identified as stressors to aquatic life in Central Appalachian coalfield streams. At present there are no aquatic life water quality criteria for TDS in the primary coal-producing Central Appalachian states (KY, VA, WV). In all three states, mining-related impacts on aquatic life have been characterized using measures of benthic macroinvertebrate community structure. Impacts of mining on aquatic life have been documented in the literature, but our understanding of impacts from TDS is confounded because elevated TDS rarely occurs independent of other stressors in coalfield streams. Potential TDS covariates in coalfield streams include acidic pH, toxic metals, sedimentation, in-stream and riparian habitat degradation, trophic structure alteration, and hydrologic modification. As a means of isolating TDS effects, we identified 17 headwater streams in Virginias coalfield region that represent a gradient of TDS concentrations, where influence from non-TDS stressors was minimized (i.e., pH between 6.0 and 9.0, low metal concentrations, reference-quality habitat, primarily forested land-use). Benthic macroinvertebrate communities were sampled from these streams in Spring 2009. Organisms were enumerated and identified to the family/lowest practicable level. These data were then used to calculate common benthic macroinvertebrate community metrics. In addition, TDS and component ions were measured for water collected concurrently with biological samples. Data were analyzed for significant associations between TDS and biological metrics. We identified stream sites with elevated TDS where influence from non-TDS stressors was minimal. Dominant components of TDS were sulfate (46% by weight, mean), bicarbonate (26%), and calcium (13%). Several benthic macroinvertebrate richness measures were correlated negatively with increasing TDS (p 0.05) within the range of TDS that we measured (28-792 mg/L). Our results suggest sulfate is a good candidate for single-parameter prediction of biological condition.

Contaminant concentrations in Asian carps, invasive species in the Mississippi and Illinois Rivers

Populations of invasive fishes quickly reach extremely high biomass. Before control methods can be applied, however, an understanding of the contaminant loads of these invaders carry is needed. We investigated differences in concentrations of selected elements in two invasive carp species as a function of sampling site, fish species, length and trophic differences using stable isotopes (δ15N, δ13C). Fish were collected from three different sites, the Illinois River near Havana, Illinois, and two sites in the Mississippi River, upstream and downstream of the Illinois River confluence. Five bighead carp (Hypophthalmichthys nobilis) and five silver carp (Hypophthalmichthys molitrix) from each site were collected for muscle tissue analyses. Freshwater mussels (Amblema plicata) previously collected in the same areas were used as an isotopic baseline to standardize fish results among sites. Total fish length, trophic position, and corrected 13C, were significantly related to concentrations of metals in muscle. Fish length explained the most variation in metal concentrations, with most of that variation related to mercury levels. This result was not unexpected because larger fish are older, giving them a higher probability of exposure and accumulation of contaminants. There was a significant difference in stable isotope profiles between the two species. Bighead carp occupied a higher trophic position and had higher levels of corrected 13C than silver carp. Additionally bighead carp had significantly lower concentrations of arsenic and selenium than silver carp. Stable isotope ratios of nitrogen in Asian carp were at levels that are more commonly associated with higher-level predators, or from organisms in areas containing high loads of wastewater effluent.

Effect of test duration and feeding on relative sensitivity of genetically distinct clades of Hyalella azteca

The amphipod Hyalella azteca is widely used in ecotoxicology laboratories for the assessment of chemical risks to aquatic environments, and it is a cryptic species complex with a number of genetically distinct strains found in wild populations. While it would be valuable to note differences in contaminant sensitivity among different strains collected from various field sites, those findings would be influenced by acclimation of the populations to local conditions. In addition, potential differences in metabolism or lipid storage among different strains may confound assessment of sensitivity in unfed acute toxicity tests. In the present study, our aim was to assess whether there are genetic differences in contaminant sensitivity among three cryptic provisional species of H. azteca. Therefore, we used organisms cultured under the same conditions, assessed their ability to survive for extended periods without food, and conducted fed and unfed acute toxicity tests with two anions (nitrate and chloride) whose toxicities are not expected to be altered by the addition of food. We found that the three genetically distinct clades of H. azteca had substantially different responses to starvation, and the presence/absence of food during acute toxicity tests had a strong role in determining the relative sensitivity of the three clades. In fed tests, where starvation was no longer a potential stressor, significant differences in sensitivity were still observed among the three clades. In light of these differences in sensitivity, we suggest that ecotoxicology laboratories consider using a provisional species in toxicity tests that is a regionally appropriate surrogate.