Risk of weathered residual Exxon Valdez oil to pink salmon embryos in Prince William Sound

It has been hypothesized that pink salmon eggs incubating in intertidal streams transecting Prince William Sound (PWS) beaches oiled by the Exxon Valdez oil spill were exposed to lethal doses of dissolved hydrocarbons. Since polycyclic aromatic hydrocarbon (PAH) levels in the incubation gravel were too low to cause mortality, the allegation is that dissolved high-molecular-weight hydrocarbons (HPAH) leaching from oil deposits on the beach adjacent to the streams were the source of toxicity. To evaluate this hypothesis, we placed pink salmon eggs in PWS beach sediments containing residual oil from the Exxon Valdez oil spill and in control areas without oil. We quantified the hydrocarbon concentrations in the eggs after three weeks of incubation. Tissue PAH concentrations of eggs in oiled sediments were generally < 100 ppb and similar to background levels on nonoiled beaches. Even eggs in direct contact with oil in the sediment resulted in tissue PAH loads well below the lethal threshold concentrations established in laboratory bioassays, and very low concentrations of HPAH compounds were present. These results indicate that petroleum hydrocarbons dissolved from oil deposits on intertidal beaches are not at concentrations that pose toxic risk to incubating pink salmon eggs. The evidence does not support the hypothesis that interstitial pore water in previously oiled beaches is highly toxic.     

An Evaluation of the Toxicity of Contaminated Sediments from Waukegan Harbor, Illinois, Following Remediation

Waukegan Harbor in Illinois was designated as a Great Lakes Area of Concern due to high concentrations of sediment-associated polychlorinated biphenyls (PCBs). The objective of this study was to evaluate the toxicity of 20 sediment samples collected after remediation (primarily dredging) of Waukegan Harbor for PCBs. A 42-day whole sediment toxicity test with the amphipod Hyalella azteca (28-day sediment exposure followed by a 14-day reproductive phase) and sediment toxicity tests with Microtox(R) were conducted to evaluate sediments from Waukegan Harbor. Endpoints measured were survival, growth, and reproduction (amphipods) and luminescent light emission (bacteria). Survival of amphipods was significantly reduced in 6 of the 20 sediment samples relative to the control. Growth of amphipods (either length or weight) was significantly reduced relative to the control in all samples. However, reproduction of amphipods identified only two samples as toxic relative to the control. The Microtox basic test, conducted with organic extracts of sediments identified only one site as toxic. In contrast, the Microtox solid-phase test identified about 50% of the samples as toxic. A significant negative correlation was observed between reproduction and the concentration of three polynuclear aromatic hydrocarbons (PAHs) normalized to total organic carbon. Sediment chemistry and toxicity data were evaluated using sediment quality guidelines (consensus-based probable effect concentrations, PECs). Results of these analyses indicate that sediment samples from Waukegan Harbor were toxic to H. azteca contaminated at similar contaminant concentrations as sediment samples that were toxic to H. azteca from other areas of the United States. The relationship between PECs and the observed toxicity was not as strong for the Microtox test. The results of this study indicate that the first phase of sediment remediation in Waukegan Harbor successfully lowered concentrations of PCBs at the site. Though the sediments were generally not lethal, there were still sublethal effects of contaminants in sediments at this site observed on amphipods in long-term exposures (associated with elevated concentrations of metals, PCBs, and PAHs).     

Toxicity assessment of sediments from the Grand Calumet River and Indiana Harbor Canal in Northwestern Indiana,USA

The objective of this study was to evaluate the toxicity of sediments from the Grand Calumet River and Indiana Harbor Canal located in northwestern Indiana, USA. Toxicity tests used in this assessment included 10-day sediment exposures with the amphipod Hyalella azteca, 31-day sediment exposures with the oligochaete Lumbriculus variegatus, and the Microtox Solid-Phase Sediment Toxicity Test. A total of 30 sampling stations were selected in locations that had limited historic matching toxicity and chemistry data. Toxic effects on amphipod survival were observed in 60% of the samples from the assessment area. Results of a toxicity test with oligochaetes indicated that sediments from the assessment area were too toxic to be used in proposed bioaccumulation testing. Measurement of amphipod length after the 10-day exposures did not provide useful information beyond that provided by the survival endpoint. Seven of the 15 samples that were identified as toxic in the amphipod tests were not identified as toxic in the Microtox test, indicating that the 10-day H. azteca test was more sensitive than the Microtox test. Samples that were toxic tended to have the highest concentrations of metals, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). The toxic samples often had an excess of simultaneously extracted metals (SEM) relative to acid volatile sulfide (AVS) and had multiple exceedances of probable effect concentrations (PECs). Metals may have contributed to the toxicity of samples that had both an excess molar concentration of SEM relative to AVS and elevated concentrations of metals in pore water. However, of the samples that had an excess of SEM relative to AVS, only 38% of these samples had elevated concentration of metals in pore water. The lack of correspondence between SEM-AVS and pore water metals indicates that there are variables in addition to AVS controlling the concentrations of metals in pore water. A mean PEC quotient of 3.4 (based on concentrations of metals, PAHs, and PCBs) was exceeded in 33% of the sediment samples and a mean quotient of 0.63 was exceeded in 70% of the thirty sediment samples from the assessment area. A 50% incidence of toxicity has been previously reported in a database for sediment tests with H. azteca at a mean quotient of 3.4 in 10-day exposures and at a mean quotient of 0.63 in 28-day exposures. Among the Indiana Harbor samples, most of the samples with a mean PEC quotient above 0.63 ( i.e., 15 of 21; 71%) and above 3.4 ( i.e., 10 of 10; 100%) were toxic to amphipods. Results of this study and previous studies demonstrate that sediments from this assessment area are among the most contaminated and toxic that have ever been reported.     

Using marine bioassays to classify the toxicity of Dutch harbor sediments

A procedure was developed to assess contaminated marine sediments from Dutch harbors for possible adverse biological effects using three laboratory bioassays: A 10-d survival test with the amphipod Corophium volutator, a 14-d survival test with the heart urchin Echinocardium cordatum (adults), and the bioluminescence inhibition test with the bacterium Vibrio fischeri (Microtox solid phase test LSP]). Microtox results were mathematically corrected for the modifying influence of fine sediment particles. After a validation procedure on test performance and modifying factors, respectively, 81%, 99%, and 90% of the amphipod, heart urchin, and Microtox results were approved. Lower and upper threshold limits for biological effects were set at respectively 24 and 30% mortality for C. volutator, 27 and 35% mortality for E. cordatum, and 24 and 48 toxic units for the Microtox SP based on significant differences with control sediment and the performance of reference sediments. The bioassays clearly distinguished harbor sediments that give rise to acute effects and those that do not. Threshold limits for the amphipods, heart urchins, and bacteria were exceeded in, respectively, 9 to 17%, 33 to 40%, and 23 to 50% of the sediment samples. Highest effects were observed in sediments from the northerly harbors; there was significantly less response in sediments from the Delta Region and the port of Rotterdam (The Netherlands). The procedure outlined in this paper can be used for routine screening of contaminated dredged material that is proposed for open water disposal.     

Chemical contamination and toxicity of sediment from a coastal area receiving industrial effluents in Kuwait

The Shuaiba coastal area (12.5 × 1.5 km) was examined for contamination with total organic carbon, volatile organic matter, total petroleum hydrocarbons, polycyclic aromatic hydrocarbons, cadmium, chromium, copper, lead, nickel, vanadium, and zinc in sediment; their desorption by aqueous elution; and toxicity to aquatic biota. The pollutants were mainly accumulated in the upstream area facing Mina Al-Ahmadi refinery to Shuaiba harbour. Solid-phase Microtox assays showed severe toxicity, and the LC₅₀ was negatively correlated with most of the chemical parameters, suggesting that toxicity was the function of collective effects of the pollutants present in sediment. Sea water elutriation showed poor desorption of pollutants from sediment, and the elutriates were not found toxic to Microtox and brine shrimp larvae. Whole sediment suspension in sea water reduced the survival of fingerlings in fish bioassays. Action from Shuaiba Area Authority is required to reduce pollutant accumulation in identified depositional area on the Shuaiba coast by facilitating unrestricted water flow in the area and restricting pollutant discharge at source. Received: 15 November 2000/Accepted: 11 May 2001     

Comparing the solid phase and saline extract Microtox assays for two polycyclic aromatic hydrocarbon-contaminated soils

The performance of remedial treatments is typically evaluated by measuring the concentration of specific chemicals. By adding toxicity bioassays to treatment evaluations, a fuller understanding of treatment performance is obtained. The solid phase Microtox assay is a useful tool in characterizing the toxicity of contaminated soils and sediments. This study compares the performance of the solid phase and saline extract Microtox assays in two experiments using two soils contaminated with polycyclic aromatic hydrocarbons (PAHs). The first experiment, conducted to refine the solid phase assay procedures, evaluated sample holding times, sample replication, and reference toxicant controls. The effective concentration reducing light emission by 50% (EC50) of four samples was measured with eight replicates of each sample. Samples were stored for as long as two weeks without showing substantial changes in toxicity. For future studies, three replicates of each sample are recommended because that degree of replication yielded a statistical power of more than 95% in most samples. Phenol was a reliable reference toxicant with a mean EC50 of 21.76 and a 95% confidence interval of 15.6 to 27.9 mg/L. In a second experiment, the solid phase Microtox assay was compared to saline extract Microtox assays with mixing times ranging from 5 min to 16 h. The solid phase assay was more sensitive yielding EC50s 7 to 50 times lower than the extract EC50s. In addition, the saline extract assays displayed results that varied for mixing times of less than 2 h. Based on these two experiments, the solid phase Microtox test has proved to be a useful assay for measuring the toxicity of PAH-contaminated soils.     

Hydrocarbon composition and toxicity of sediments following the Exxon Valdez oil spill in Prince William Sound,Alaska, USA

An 1-year study of the 1989 Exxon Valdez oil spill found that spill residues on the oiled shorelines rapidly lost toxicity through weathering. After 1990, toxicity of sediments remained at only a few heavily oiled, isolated locations in Prince William Sound (AK, USA), as measured by a standard amphipod bioassay using Rhepoxynius abronius. Data from 648 sediment samples taken during the 1990 to 1993 period were statistically analyzed to determine the relationship between the total concentration of 39 parent and methyl-substituted polycyclic aromatic hydrocarbons (defined as total polycyclic aromatic hydrocarbons [TPAH]) and amphipod mortality and the effect of oil weathering on toxicity. A logistic regression model yielded estimates of the lower threshold, LC10 (lethal concentration to 10% of the population), and LC50 (median lethal concentration) values of 2,600, 4,100, and 10,750 ng/g TPAH (dry wt), respectively. Estimates of the threshold and LC50 values in this field study relate well to corresponding sediment quality guideline (SQG) values reported in the literature. For sediment TPAH concentrations >2,600 ng/g, samples with high mortality values (>90%) had relatively high fractions of naphthalenes and those with low mortality (<20%) had relatively high fractions of chrysenes. By 1999, the median sediment TPAH concentration of 117 ng/g for the post-1989 worst-case sites studied were well below the 2,600 ng/g toxicity threshold value, confirming the lack of potential for long-term toxic effects. Analysis of biological community structure parameters for sediment samples taken concurrently found that species richness and Shannon diversity decreased with increasing TPAH above the 2,600 ng/g threshold, demonstrating a correspondence between sediment bioassay results and biological community effects in the field. The low probability of exposure to toxic concentrations of weathered spill residues at the worst-case sites sampled in this study is consistent with the rapid overall recovery of shoreline biota observed in 1990 to 1991.     

Sediment quality in the Atlantic coast of Spain

Sediments from the Atlantic coast of Spain have been studied to evaluate environmental quality by using an integrated approach including chemical and toxicological data. Sediment samples were collected in four littoral ecosystems located in Spain, Bay of Cádiz, Guadalquivir River estuary, Ría of Huelva, and Ría of Coru?a. To characterize the sediments, organic carbon, granulometric content, total sulfide, eight trace metals (Hg, Cd, Pb, Cu, Zn, As, Ni, and Cr), polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs) were measured. The toxicity of sediments was assessed with the amphipod Ampelisca brevicornis, the clam Ruditapes philippinarum, juveniles of the fish Solea senegalensis, populations of the estuarine rotifer Brachionus plicatilis, and populations of the bacterium Vibrio fischeri (Microtox). The results obtained show that in general, stations located in the Ría of Huelva were associated with heavy metal contamination and with the highest toxicity. Only chronic toxicity tests were capable of identifying the effects associated with PCB concentrations. The sediment quality guidelines calculated by means of a multivariate analysis approach for contaminants not associated with biological effects (mg/kg) are Hg, 0.54; Cd, 0.51; Pb, 260; Cu, 209; Zn, 513; As, 27.4; and total PCBs, 0.05.     

An Evaluation of Polycyclic Aromatic Hydrocarbon (PAH) Runoff from Highways Into Estuarine Wetlands of South Carolina

This study investigated the concentrations and potential toxicity of polycyclic aromatic hydrocarbons (PAHs) associated with highway runoff into adjacent estuarine wetlands from road segments representing three levels of average daily traffic (ADT): low (<5,000 ADT), moderate (10,000–15,000 ADT), and high use (>25,000 ADT) based on SC Department of Transportation data. Sediments from three estuarine wetland habitats (tidal creeks, Spartina marsh, and mud flats) adjacent to these road segments were sampled to represent nine highway use class/habitat type combinations. Surficial sediments were collected at 3, 25, and 50 meters from the upland/wetland interface along transects established perpendicular to the road at each site, with additional samples taken from the road berm. Average PAH concentrations, representing 25 compounds, ranged from 3.9 to 11,000 ng/g dry weight. Berm samples had significantly greater total PAH concentrations than samples taken in any of the wetland habitats. Average total PAH concentrations decreased with increasing distance from the road berm within the wetland habitats sampled, but the differences were not statistically significant. Average total PAH concentrations also were not significantly different among the wetland habitats compared. Analysis of PAH profiles indicated that the PAH source was dominated by pyrogenic combustion products rather than from petrogenic sources. This, combined with the presence of dibenzothio-phene, which is a tire oxidation product, indicated that the primary source of PAHs was related to vehicles. Two sites with total PAH concentrations exceeding published bioeffects levels were resampled for bioassay tests using the amphipod Ampelisca verrilli, the polychaete Streblospio benedicti, and the clam, Mercenaria mercenaria, with the first two assays conducted under UV lighting since previous studies had demonstrated enhanced UV toxicity of PAHs for these species. No toxicity was observed in the amphipod or polychaete assays. Toxicity was observed in the juvenile clam assay at one site, possibly due to the combined effects of PAHs and other contaminants present.     

A DNA-based assay for toxic chemicals in wastewater

Chemical toxicants, particularly metal ions, are a major contaminant in global waterways. Live-organism bioassays used to monitor chemical toxicants commonly involve measurements of activity or survival of a freshwater cladoceran (Ceriodaphnia dubia) or light emitted by the marine bacterium Vibrio fischeri, used in the commercial Microtox? bioassay. Here we describe a novel molecule-based assay system employing DNA as the chemical biosensor. Metals bind to DNA, causing structural changes that expel a bound (intercalated) fluorescent reporter dye. Analyses of test data using 48 wastewater samples potentially contaminated by metal ions show that the DNA-dye assay results correlate with those from C. dubia and Microtox bioassays. All three assays exhibit additive, antagonistic, and synergistic responses that cannot be predicted by knowing individual metal concentrations. Analyses of metals in these samples imply the presence of chemical toxicants other than metal ions. The DNA-dye assay is robust, has a 12-month shelf life, and is only slightly affected by sample pH in the range 4 to 9. The assay is completed in a matter of minutes, and its portability makes it well suited as a screening assay for use in the field. We conclude that the DNA-dye test is a surrogate bioassay suitable for screening chemical toxicity.     

Heterocyclic compounds: toxic effects using algae, daphnids, and the Salmonella/microsome test taking methodical quantitative aspects into account

Heterocyclic aromatic hydrocarbons containing nitrogen, sulfur, or oxygen (NSO-HET), have been detected in air, soil, sewage sludge, marine environments, and freshwater sediments. Since toxicity data on this class of substances are scarce, the present study focuses on possible implications NSO-HET have for ecotoxicity (algae and daphnids) and mutagenicity (Salmonella/microsome test). A combination of bioassays and chemical-analytical quantification of the test compounds during toxicity assays should aid in determination of the hazard potential. Samples of the test concentrations of 14 NSO-HET were taken at the beginning and end of the bioassays; these samples were then quantified by high-performance liquid chromatography. The toxicity potential of the substances was evaluated and compared with the toxicity calculated with the nominal concentrations. Significantly different results were obtained primarily for volatile or highly hydrophobic NSO-HET. The concentration of heterocyclic hydrocarbons can change significantly during the algae and Daphnia test. The EC50 values (effective concentration value: the concentration of a chemical that is required to produce a 50% effect) calculated with the nominal concentrations underestimate the toxicity by a factor of up to 50. Prioritizing the tested compounds according to toxicity, the mutagenic and toxic compounds quinoline, 6-methylquinoline, and xanthene have to be listed first. The greatest ecotoxic potential on algae and daphnids was determined for dibenzothiophene followed by acridine. In the Daphnia magna immobilization test, benzofuran, dibenzofuran, 2-methylbenzofuran, and 2,3-dimethylbenzofuran and also carbazole are ecotoxicologically relevant with EC50 values below 10 mg/L. These substances are followed by indole with a high ecotoxic effect to daphnids and less effect to algae. Only minor toxic effects were observed for 2-methylpyridine and 2,4,6-trimethylpyridine.     

Toxicity of oil sands to early life stages of fathead minnows (Pimephales promelas)

The present study examines the effects of exposure to oil sands on the early life stages (ELS) of fathead minnows (Pimephales promelas). Sediments within and outside natural oil sand deposits were collected from sites along the Athabasca River (AB, Canada). The ELS toxicity tests were conducted with control water, natural oil sands, reference sediments, and oil-refining wastewater pond sediments. Eggs and larvae were exposed to 0.05 to 25.0 g sediment/L and observed for mortality, hatching, malformations, growth, and cytochrome P4501A induction as measured by immunohistochemistry. Natural bitumen and wastewater pond sediments caused significant hatching alterations and exposure-related increases in ELS mortality, malformations, and reduced size. Larval deformities included edemas, hemorrhages, and spinal malformations. Exposure to reference sediments and controls showed negligible embryo mortality and malformations and excellent larval survival. Sediment analyses using gas chromatography-mass spectrometry revealed high concentrations of alkyl-substituted polyaromatic hydrocarbons (PAHs) compared to unsubstituted PAHs in natural oil sands (220-360 microg/g) and oil-mining wastewater pond sediments (1,300 microg/g). The ELS sediment toxicity tests are rapid and sensitive bioassays that are useful in the assessment of petroleum toxicity to aquatic organisms.     

Use of the Ciliated Protozoan Tetrahymena pyriformis for the Assessment of Toxicity and Quantitative Structure–Activity Relationships of Xenobiotics: Comparison with the Microtox Test

Cytotoxicity and quantitative structure-activity relationships of 13 inorganic and 21 organic substances were determined using three bioassays performed on the ciliated protozoan Tetrahymena pyriformis and the luminescent bacterium Vibrio fischeri. The best concordance of toxicity results was observed between the T. pyriformis FDA--esterase activity and population growth inhibition tests for the organic compounds. The sensitivity of these two assays is compared with that of the Microtox test. The T. pyriformis FDA test showed a high sensitivity is most cases. The aim of the current research was to determine whether the relative toxicity of metal ions and organic molecules, with these three bioassays, was predictable using three ion characteristics and hydrophobicity, respectively. For metal ions, the variable that best modeled the toxicity data obtained with the two T. pyriformis tests was the softness index [sigma(p), i.e., (coordinate bond energy of the metal fluoride--coordinate bond energy of the metal iodide)/(coordinate bond energy of the metal fluoride)]. No correlation was found with the Microtox test. For organic compounds, a significant correlation was observed between the hydrophobicity coefficient and the toxicity data. This correlation is closer with the two tests using Tetrahymena.     

Behavioral response of Corophium volutator relative to experimental conditions, physical and chemical disturbances

The preference/avoidance behavioral response of a widely used amphipod in toxicity tests, Corophium volutator, was investigated in relation to the presence of anthropogenic physical or chemical materials in sediments. Exposure conditions, including the density of amphipods, the depth of sediments, amount of overlying water, and exposure time, were examined for their influence on amphipods' preference for field sediments and avoidance of coarse sand. It was shown that these variables did not affect the response; thus, conditions similar to published standard toxicity tests were chosen. A gradient of sediments spiked with potential habitat disturbances that can be found on a beach or in contaminated sediments, such as those in harbors, were tested. These substances included sand, seaweed, burned wood, coal, crankcase oil, and diesel oil. To enhance the interpretation of results and decrease the variability observed when tests were conducted at different times over the summer, exposures were performed over a gradient of spike material in reference sediments. We conclude that physical obstacles added to reference sediments lead to less correlation with the behavioral response than observed with chemical interferences. Amphipods' behavior ranked harbor sediments similarly to previous studies concerning the health of intertidal mussels collected in proximity to the sediments sites. For five sites, preference of reference sediments was observed until the level of polycyclic aromatic hydrocarbons in diluted harbor sediments reached the Canadian Council of Ministers of the Environment sediment quality guidelines.     

Hydrobia ulvae feeding rates: A novel way to assess sediment toxicity

Standard acute toxicity tests are widely used to assess contaminated sediments. However, such tests last 10 d or more and only provide information regarding lethality. Here, we present data concerning the use of a 28-d growth test and a 24-h test using feeding rate, as measured by egestion rate, of the marine snail Hydrobia ulvae. The test was used to assess the toxicity of estuarine sediments from a gradient of heavy metal contamination, and its sensitivity and ease of use were compared with those of 10-d tests using the amphipod crustacean Corophium volutator. Mortality of C. volutator and H. ulvae in 10-d lethal toxicity tests showed similar patterns of sensitivity. Lethality tests with both species showed no effects when carried out using sediments from a number of sites at which ecological impacts are known to occur. By contrast, growth over 28 d in H. ulvae was reduced at all sites where other studies have detected adverse ecological effects. Feeding rate after 24 h also was decreased at moderately contaminated sites where sediments were not acutely toxic, and it was a very good predictor of 28-d growth (r2 = 0.74). Both tests were straightforward to carry out, so H. ulvae has considerable potential as a test organism for chronic toxicity.     

Assessment of genotoxic activity of petroleum hydrocarbon-bioremediated soil

The relationship between toxicity and soil contamination must be understood to develop reliable indicators of environmental restoration for bioremediation. Two bacterial rapid bioassays, SOS chromotest and the umu test with and without metabolic activation (S-9 mixture), were used to evaluate the genotoxicity of petroleum hydrocarbon-contaminated soil following bioremediation treatment. The soil was taken from an engineered biopile at the Czechowice-Dziedzice Polish oil refinery (CZOR). The bioremediation process in the biopile lasted 4 years, and the toxicity measurements were done after this treatment. Carcinogens detected in the soil, polyaromatic hydrocarbons (PAHs), were reduced to low concentrations (2mg/kg dry wt) by the bioremediation process. Genotoxicity was not observed for soils tested with and without metabolic activation by a liver homogenate (S-9 mixture). However, the umu test was more sensitive than the SOS chromotest in the analysis of petroleum hydrocarbon-bioremediated soil. Analytical results of soil used in the bioassays confirmed that the bioremediation process reduced 81% of the petroleum hydrocarbons including PAHs. We conclude that the combined test systems employed in this study are useful tools for the genotoxic examination of remediated petroleum hydrocarbon-contaminated soil.     

Endocrine disrupting, mutagenic, and teratogenic effects of upper Danube River sediments using effect-directed analysis

Effect-directed analysis (EDA) can be useful in identifying and evaluating potential toxic chemicals in matrixes. Previous investigations of extracts of sediments from the upper Danube River in Germany revealed acute nonspecific and mechanism-specific toxicity as determined by several bioassays. In the present study, EDA was used to further characterize these sediments and identify groups of potentially toxic chemicals. Four extracts of sediments were subjected to a novel fractionation scheme coupled with identification of chemicals to characterize their ability to disrupt steroidogenesis or cause mutagenic and/or teratogenic effects. All four whole extracts of sediment caused significant alteration of steroidogenesis and were mutagenic as well as teratogenic. The whole extracts of sediments were separated into 18 fractions and these fractions were then subjected to the same bioassays as the whole extracts. Fractions 7 to 15 of all four extracts were consistently more potent in both the Ames fluctuation and H295R assays. Much of this toxicity could be attributed to polycyclic aromatic hydrocarbons, sterols, and in fraction 7-naphthoic acids. Because the fraction containing polychlorinated biphenyls, polychlorodibenzodioxin/furan, dichlorodiphenyltrichloroethane, and several organophosphates did not cause any observable effects on hormone production or a mutagenic response, or were not detected in any of the samples, these compounds could be eliminated as causative agents for the observed effects. These results demonstrate the value of using EDA, which uses multiple bioassays and new fractionation techniques to assess toxicity. Furthermore, to our knowledge this is the first study using the recently developed H295R assay within EDA strategies.     

Comparative Bioaccumulation of Chlorinated Hydrocarbons from Sediment by Two Infaunal Invertebrates

Bioaccumulation of chlorinated hydrocarbons (CHs) from field-contaminated sediments by two infaunal invertebrates, Rhepoxynius abronius (a non–deposit feeding amphipod) and Armandia brevis (a nonselective, deposit-feeding polychaete), was examined and species responses were compared. Sediments were selected over a large geographical area of the Hudson-Raritan estuary to assess the potential for bioaccumulation from a typical urban estuary. Unlike polycyclic aromatic hydrocarbons (PAHs) from these sediments, concentrations of CHs in interstitial water (IW) indicated that partition coefficients (K_oc) were generally as expected, especially when based on predicted, nonsorbed, interstitial water CH concentrations (IW_free). Correlations between amphipod and polychaete tissue residues revealed that these species were responding similarly to a gradient of CH concentrations in sediment. While tissue residues and BAF_loc (lipid/organic carbon normalized bioaccumulation factor) values for the trichlorobiphenyls were similar for both species, accumulation in the polychaete was three to 10 times higher for the more hydrophobic PCBs, which was attributed to differences in the route of exposure. A negative correlation between the bioaccumulation factor (BAF) and total organic carbon (TOC) was found for both species, which was expected according to equilibrium partitioning theory. Because it was assumed that the amphipod was not feeding in these tests and the polychaete was ingesting sediment, comparison of their tissue residues and bioaccumulation factors was useful for highlighting the importance of sediment ingestion, especially for short-term, nonequilibrium exposures. These results may also help elucidate the limitations associated with assessing bioaccumulation and the resultant toxic response in standard 10-day toxicity tests with similar invertebrates. Received: 1 February 1997/Accepted: 30 June 1997     

Predictions of Sediment Toxicity Using Consensus-Based Freshwater Sediment Quality Guidelines

The objectives of this study were to compare approaches for evaluating the combined effects of chemical mixtures on the toxicity in field-collected sediments and to evaluate the ability of consensus-based probable effect concentrations (PECs) to predict toxicity in a freshwater database on both a national and regional geographic basis. A database was developed from 92 published reports, which included a total of 1,657 samples with high-quality matching sediment toxicity and chemistry data from across North America. The database was comprised primarily of 10- to 14-day or 28- to 42-day toxicity tests with the amphipod Hyalella azteca (designated as the HA10 or HA28 tests) and 10- to 14-day toxicity tests with the midges Chironomus tentans or C. riparius (designated as the CS10 test). Mean PEC quotients were calculated to provide an overall measure of chemical contamination and to support an evaluation of the combined effects of multiple contaminants in sediments. There was an overall increase in the incidence of toxicity with an increase in the mean quotients in all three tests. A consistent increase in the toxicity in all three tests occurred at a mean quotient > 0.5, however, the overall incidence of toxicity was greater in the HA28 test compared to the short-term tests. The longer-term tests, in which survival and growth are measured, tend to be more sensitive than the shorter-term tests, with acute to chronic ratios on the order of six indicated for H. azteca. Different patterns were observed among the various procedures used to calculate mean quotients. For example, in the HA28 test, a relatively abrupt increase in toxicity was associated with elevated polychlorinated biphenyls (PCBs) alone or with elevated polycyclic aromatic hydrocarbons (PAHs) alone, compared to the pattern of a gradual increase in toxicity observed with quotients calculated using a combination of metals, PAHs, and PCBs. These analyses indicate that the different patterns in toxicity may be the result of unique chemical signals associated with individual contaminants in samples. Though mean quotients can be used to classify samples as toxic or nontoxic, individual quotients might be useful in helping identify substances that may be causing or substantially contributing to the observed toxicity. An increase in the incidence of toxicity was observed with increasing mean quotients within most of the regions, basins, and areas in North America for all three toxicity tests. The results of these analyses indicate that the consensus-based PECs can be used to reliably predict toxicity of sediments on both a regional and national basis.     

Performance and sensitivity of rapid sublethal sediment toxicity tests with the amphipod Melita plumulosa and copepod Nitocra spinipes

Sublethal whole-sediment toxicity tests are an important tool for assessing the potential effects of contaminated sediments. However, the longer duration required for evaluating potential chronic effects may increase endpoint variability and test costs compared to survival endpoints. In the present study we compare the performance and sensitivity to contaminants of 10-d sublethal sediment toxicity tests with the amphipod Melita plumulosa and harpacticoid copepod Nitocra spinipes. For both tests, sublethal effects were consistently observed when sediment contaminant concentrations exceeded sediment quality guideline (SQG) concentrations. The response of these bioassays in metal-contaminated sediments was shown to conform ideally with respect to the mean SQG quotient calculated on the basis of the Australian and New Zealand lower SQG trigger value, with toxicity being observed only in those sediments where the mean quotient exceeded one. Better predictions of nontoxicity were obtained when dilute acid-extractable rather than total metal concentrations were used. Using the upper SQG, toxicity frequently occurred at mean quotients below one. The effects were generally consistent with predictions from the acid-volatile sulfide and simultaneously extracted metal model. Effects on reproduction of M. plumulosa were detected for sediments that did not cause effects on survival and highlighted the environmental relevance and importance of using these sublethal endpoints. When using four replicates for M. plumulosa and five replicates for N. spinipes, the endpoint variability (standard error) was less than 10%. Variations in sediment particle size and organic carbon content did not affect endpoint variability. Both species are relatively easily cultured in the laboratory, and the estimated effort and cost of achieving the sublethal endpoints is 1.5 times that of the acute survival test endpoints.