Identifying the causes of oil sands coke leachate toxicity to aquatic invertebrates

A previous study found that coke leachates (CL) collected from oil sands field sites were acutely toxic to Ceriodaphnia dubia; however, the cause of toxicity was not known. Therefore, the purpose of this study was to generate CL in the laboratory to evaluate the toxicity response of C. dubia and perform chronic toxicity identification evaluation (TIE) tests to identify the causes of CL toxicity. Coke was subjected to a 15-d batch leaching process at pH 5.5 and 9.5. Leachates were filtered on day 15 and used for chemical and toxicological characterization. The 7-d median lethal concentration (LC50) was 6.3 and 28.7% (v/v) for pH 5.5 and 9.5 CLs, respectively. Trace element characterization of the CLs showed Ni and V levels to be well above their respective 7-d LC50s for C. dubia. Addition of ethylenediaminetetraacetic acid significantly (p?≤?0.05) improved survival and reproduction in pH 5.5 CL, but not in pH 9.5 CL. Cationic and anionic resins removed toxicity of pH 5.5 CL only. Conversely, the toxicity of pH 9.5 CL was completely removed with an anion resin alone, suggesting that the pH 9.5 CL contained metals that formed oxyanions. Toxicity reappeared when Ni and V were added back to anion resin-treated CLs. The TIE results combined with the trace element chemistry suggest that both Ni and V are the cause of toxicity in pH 5.5 CL, whereas V appears to be the primary cause of toxicity in pH 9.5 CL. Environmental monitoring and risk assessments should therefore focus on the fate and toxicity of metals, especially Ni and V, in coke-amended oil sands reclamation landscapes.     

Acute and chronic toxicity of five selective serotonin reuptake inhibitors in Ceriodaphnia dubia

Contamination of surface waters by pharmaceutical chemicals has raised concern among environmental scientists because of the potential for negative effects on aquatic organisms. Of particular importance are pharmaceutical compounds that affect the nervous or endocrine systems because effects on aquatic organisms are possible at low environmental concentrations. Selective serotonin reuptake inhibitors (SSRIs) are drugs used to treat clinical depression in humans, and have been detected in low concentrations in surface waters. In this investigation, the acute and chronic toxicity of five SSRIs (fluoxetine, Prozac; fluvoxamine, Luvox; paroxetine, Paxil; citalopram, Celexa; and sertraline, Zoloft) were evaluated in the daphnid Ceriodaphnia dubia. For each SSRI, the 48-h median lethal concentration (LC50) was determined in three static tests with neonate C. dubia, and chronic (8-d) tests were conducted to determine no-observable-effect concentrations (NOEC) and lowest-observable-effect concentrations (LOEC) for reproduction endpoints. The 48-h LC50 for the SSRIs ranged from 0.12 to 3.90 mg/L and the order of toxicity of the compounds was (lowest to highest): Citalopram, fluvoxamine, paroxetine, fluoxetine, sertraline. Mortality data for the 8-d chronic tests were similar to the 48-h acute data. The SSRIs negatively affected C. dubia reproduction by reducing the number of neonates per female, and for some SSRIs, by reducing the number of broods per female. For sertraline, the most toxic SSRI, the LOEC for the number of neonates per female was 0.045 mg/L and the NOEC was 0.009 mg/L. Results indicate that SSRIs can impact survival and reproduction of C. dubia; however, only at concentrations that are considerably higher than those expected in the environment.     

Identification of chlorfenvinphos toxicity in a municipal effluent in Sydney, New South Wales, Australia

Acute toxicity in a municipal sewage treatment plant in Sydney, New South Wales, Australia, was traced to chlorfenvinphos, an organophosphorous pesticide. Toxicity identification evaluation procedures led to the tentative identification of chlorfenvinphos as the toxic contaminant in the sample. Subsequent analytical verification revealed 0.95 microg/L of chlorfenvinphos in the effluent sample, and spiking studies confirmed that it accounted for the observed toxicity. The 48-h median lethal concentration of chlorfenvinphos to Ceriodaphnia dubia averaged 0.28 microg/L (n = 4). Source-control measures were effective at eliminating chlorfenvinphos and associated toxicity from the discharge.     

Acute and chronic toxicity of nickel to a cladoceran (Ceriodaphnia dubia) and an amphipod (Hyalella azteca)

This study evaluated acute and chronic nickel (Ni) toxicity to Ceriodaphnia dubia and Hyalella azteca with the objective of generating information for the development of a biotic ligand model for Ni. Testing with C. dubia was used to evaluate the effect of ambient hardness on Ni toxicity, whereas the larger H. azteca was used to derive lethal body burden information for Ni toxicity. As was expected, acute C. dubia median lethal concentrations (LC50s) for Ni increased with increasing water hardness. The 48-h LC50s were 81, 148, 261, and 400 microg/L at hardnesses of 50, 113, 161, and 253 mg/L (as CaCO3), respectively. Ceriodaphnia dubia was found to be significantly more sensitive in chronic exposures than other species tested (including other daphnids such as Daphnia magna); chronic toxicity was less dependent on hardness than was acute toxicity. Chronic 20% effective concentrations (EC20s) were estimated at <3.8, 4.7, 4.0, and 6.9 microg/L at hardnesses of 50, 113, 161, and 253 mg/L, respectively. Testing with H. azteca resulted in a 96-h LC50 of 3,045 microg/L and a 14-d EC20 of 61 microg/L at a hardness of 98 mg/L (as CaCO3). Survival was more sensitive than was growth in the chronic study with H. azteca. The 20% lethal accumulation effect level based on measured Ni body burdens was 247 nmol/g wet weight.     

Toxicity of Euphorbia milii latex and niclosamide to snails and nontarget aquatic species

The toxicity of Euphorbia milii molluscicidal latex and niclosamide (NCL) to target snails (Biomphalaria glabrata and Biomphalaria tenagophila) and nontarget aquatic organisms is evaluated. Planorbidae snails were killed by very low concentrations of lyophilized latex (48-h LC(50), mg/L: B. glabrata, 0.12; B. tenagophila, 0.09; Helisoma duryi, 0.10). Latex was less toxic (48-h LC(50) or EC(50), mg/L) to oligochaeta (Tubifex tubifex, 0.31), planktonic crustacea (Daphnia similis, 0.38; C. dubia, 1.07; Artemia sp., 0.93), and fishes (Danio rerio, 0.96; Poecilia reticulata, 1. 39), and considerably less toxic to Ampullariidae snails (Pomacea sp. , 10.55) and frog tadpoles (Rana catesbeiana, 7.50). Latex (up to 100 mg/L) was not toxic to bacteria (P. putida and V. fischeri), algae (Selenastrum capricornutum and Chlorella vulgaris), and mosquito larvae (Anopheles albitarsis, Aedes aegypti, Aedes fluviatilis). NCL was very toxic (48-h LC(50) or EC(50), mg/L) to Planorbidae snails (B. glabrata, 0.15, B. tenagophila, 0.13; H. duryi, 0.10), T. tubifex (0.11), crustacea (D. similis, 0.19; Ceriodaphnia dubia, 0.47; Artemia sp. 0.18), fishes (D. rerio, 0.25; P. reticulata, 0.29), R. catesbeiana (0.16), and Pomacea sp. (0.76). NCL was toxic to bacteria, algae (96-h IC(50), mg/L: S. capricornutum, 0.34; C. vulgaris, 1.23) and slightly toxic to mosquito larvae. In conclusion, E. milii latex, as compared with the reference molluscicide niclosamide, presents a higher degree of selectivity toward snails which are intermediate hosts of Schistosoma trematodes.     

Toxicity of raw and neutralized bauxite refinery residue liquors to the freshwater cladoceran Ceriodaphnia dubia and the marine amphipod Paracalliope australis

The extraction of alumina from bauxite produces a highly toxic residue, termed bauxite refinery residue (BRR) or red mud. The toxicity of this material is due to chemical and biological effects of high pH, alkalinity, electrical conductivity (EC), and Na(+) and Al(3+) concentrations. Several neutralization techniques may allow BRR to be used for environmental remediation. The present study investigated standardized 48-h acute toxicity tests with a freshwater cladoceran, Ceriodaphnia dubia, and a marine amphipod, Paracalliope australis, against raw supernatant BRR liquor (RL) versus liquors neutralized with acid (ANL), CO(2) (CNL), seawater (SNL), and a hybrid method (HNL). Based on 48-h LC50 values, the toxicity of the liquors to C. dubia increased in the following order; HNL ≤ SNL< ANL ≤ CNL < RL, with comparable responses from P. australis. The high toxicity of RL likely is due to high pH (≈ 12), alkalinity, and Al concentration. Toxicity of CNL likely is due to high EC and alkalinity. Sulfate and Na(+) concentrations are considered sources of toxicity in ANL. Seawater-neutralized liquor and HNL were considerably less toxic to both test species. These data provide evidence of the acute lethal toxicity of raw supernatant liquor from BRR and four neutralized supernatant liquors to the freshwater cladoceran C. dubia and the marine amphipod P. australis, providing valuable baselines for further ecotoxicological investigations of BRR materials in aquatic environments.     

Effects of ligand-bound silver on Ceriodaphnia dubia

In aqueous media, ionic silver concentrations are low and transport occurs in the colloidal phase. In the aquatic environment, silver forms 1:1 complexes with thiol-containing compounds such as cysteine and glutathione. In order to quantitatively characterize the risk associated with silver in aquatic ecosystems, the bioavailabilities and toxicities of silver cysteinate and silver glutathionate were characterized. Static renewal bioassays were conducted with Ceriodaphnia dubia to estimate chronic toxicity, using mortality and reproduction as endpoints. Silver nitrate was the most lethal compound, with a median lethal concentration (8-d LC50) of 0.32 microg Ag/L (95% confidence interval [CI] = 0.19-0.54). The 48-h LC50 for AgNO3 was 0.5 microg/L and did not change significantly through 8 d. The presence of food in the bioassay did not change the 48-h LC50 for AgNO3. Silver glutathionate (AgGSH) and silver cysteinate (AgCys) induced less mortality during the 8-d bioassay. Silver cysteinate appeared to have the greatest effect on fecundity, with a no-observable-effect concentration (NOEC) less than 0.001 microg/L. Silver nitrate and AgGSH had lowest-observable-effect concentration (LOEC) values (nominal concentrations) of 0.01 and 0.6 microg/L, respectively. Results indicate that the ligand-bound silver in these laboratory studies is bioavailable and impairs reproduction of C. dubia at low aqueous concentrations.     

Effects of depleted uranium on the health and survival of Ceriodaphnia dubia and Hyalella azteca

Depleted uranium (DU) has been used as a substitute for the fissionable enriched uranium component of atomic weapons tested at Los Alamos National Laboratory (LANL) (Los Alamos, NM, USA) since the early 1950s, resulting in considerable concentrations of DU in the soils within the test sites. Although the movement of DU into major aquatic systems has been shown to be minimal, there are many small-order ephemeral streams and areas of standing water in canyons throughout LANL that may be affected by inputs of DU via runoff, erosion, and leaching. Ninety-six-hour acute and 7-d chronic toxicity assays were conducted to measure the toxicity of DU on survival and reproduction of Ceriodaphnia dubia. A 14-d water-only assay was conducted to measure survival and growth of Hyalella azteca. The estimated median lethal concentration (LC50) to produce 50% mortality of the test population for the 96-h Ceriodaphnia dubia assay was 10.50 mg/L. Reproductive effects occurred at a lowest-observable-effect concentration > or = 3.91 mg/L with a no-observable-effect concentration of 1.97 mg/L. The estimated 14-d LC50 for the Hyalella azteca assay was 1.52 mg/L. No significant relationship was detected between growth and DU concentrations. Concentrations at which toxicity effects were observed in this study for both invertebrates exceeded concentrations of total uranium observed in runoff from LANL lands. Thus, it is likely that current runoff levels of uranium do not pose a threat to these types of aquatic invertebrates.     

A screening method for toxicity identification evaluation on an industrial effluent using Chelex-100 resin and chelators for specific metals

Toxicity of an industrial effluent was characterized using a toxicity identification method established at our research institute. Toxicity was evaluated using the Ceriodaphnia dubia survival test. The industrial effluent chosen in the present study had toxic effects on C. dubia before treatment. The effluent was first filtered to remove suspended solids (F-treatment). Activated charcoal was then added to the effluent to adsorb organic substances (AC-treatment), followed by treatment of the supernatant with Chelex-100 resin to remove di- and trivalent cations, including transition metals (C100-treatment). The effluent exhibited a toxic effect on C. dubia even after the AC-treatment, but it was no longer toxic after the C100-treatment, indicating that the effluent contained cations that affect C. dubia survival. To further identify the metals responsible for the toxicity, benzoin-alpha-oxime or dimethylglyoxime was added to the effluent to chelate specific cations. The toxicity of the effluent was eliminated by addition of dimethylglyoxime but not significantly so by addition of benzoin-alpha-oxime, suggesting that the toxicants in the effluent strongly formed complexes with dimethylglyoxime. These results combined with those of metal analysis strongly suggest that nickel might be the noxious agent. The toxicity identification method described in this paper is effective for the identification of metal toxicants in industrial effluents. The method using insoluble chelating resins and chelators for specific metals would serve as a useful addition to the standard toxicity identification evaluation procedure.     

Comparative acute toxicity of potassium permanganate to nontarget aquatic organisms

Potassium permanganate (KMnO4) is used worldwide in freshwater pond aquaculture for treatment and prevention of waterborne external parasitic, bacterial, and fungal diseases. Nevertheless, KMnO4 has not been approved by the U.S. Food and Drug Administration, and insufficient information exists to allow evaluation of the environmental risk of KMnO4 exposures. Limited data exist concerning KMnO4 toxicity to nontarget species in systems receiving aquaculture effluent from treated ponds. The goal of this research is to generate effects data for use in developing an ecological risk assessment of KMnO4. Toxicity tests were used to compare the relative sensitivities of five standard aquatic test species to KMnO4. Acute toxicity test results using synthetic moderately hard water show static 96-h mean median lethal concentration (LC50) values +/- standard deviation (SD) of 0.058 +/- 0.006 mg/L for Ceriodaphnia dubia, 0.053 +/- 0.009 mg/L for Daphnia magna, 2.13 +/- 0.07 mg/L for Pimephales promelas, 4.74 +/- 1.05 mg/L for Hyalella azteca, and 4.43 +/- 0.79 mg/L for Chironomus tentans. Most of these values are below the recommended KMnO4 treatment rate of at least 2.0 mg/L or 2.5 times the water's potassium permanganate demand (PPD; an estimation of the available reducing agents in the exposure water), suggesting significant environmental risk. However, repeating these laboratory tests using pond water resulted in significantly reduced toxicity, with static 96-h mean LC50 values (+/-SD) of 2.39 +/- 0.36 mg/L for C. dubia, 1.98 +/- 0.12 mg/L for D. magna, 11.22 +/- 1.07 mg/L for P. promelas, 13.55 +/- 2.24 mg/L for H. azteca, and 12.30 +/- 2.83 mg/L for C. tentans. The PPD of synthetic moderately hard water was 0.329 +/- 0.114 mg/L; however, pond water PPD was 5.357 +/- 0.967 mg/L. The effective disease-treating dose based on 2.5 times the PPD would thus be 0.823 and 13.392 mg KMnO4/L, respectively, exceeding the LC50 for most of these nontarget organisms, even in pond water, immediately after treatment.     

Role of piperonyl butoxide in the toxicity of chlorpyrifos to Ceriodaphnia dubia and Xenopus laevis

The use of chemical inhibitors/inducers is one of the strategies employed to determine whether a particular metabolic pathway is involved in the metabolism of a xenobiotic. The objective of this study was to assess the role of piperonyl butoxide (PBO) on the toxicity of an organophosphorus insecticide, chlorpyrifos (CPF) to two species, Ceriodaphnia dubia (waterflea) and Xenopus laevis (South African clawed frog). Chlorpyrifos was highly toxic to C. dubia (48-h LC50: 0.05 microg/L) in comparison with X. laevis (96-h LC50: 2410 microg/L). Piperonyl butoxide at 200 microg/L reduced the toxicity of chlorpyrifos to C. dubia by a factor of 6. Piperonyl butoxide at 3000 microg/L also reduced the toxicity of CPF to X. laevis with respect to mortality and malformations. Acetylcholinesterase (AChE) activity was used as a biomarker to further assess the role of PBO in chlorpyrifos toxicity. X. laevis exposed to CPF and PBO exhibited a biphasic response in terms of AChE activity with an initial increase in the AChE activity followed by a drastic decrease. The results from the present study indicate that C. dubia and X. laevis have the capability to metabolize chlorpyrifos via cytochromes P450 mediated reactions. The results also indicate that the use of the biomarker AChE is useful in determining metabolic processes of organophosphorus insecticides, which require metabolic activation.     

Aquatic toxicity of nitrogen mustard to Ceriodaphina dubia, Daphnia magna, and Pimephales promelas

Investigation of toxicity of mustard compounds to aquatic organisms has been limited although their effects on terrestrial mammal species have been well studied. In this study, the 48-h LC50 values of nitrogen mustard (HN2) are reported for two aquatic invertebrate species (Daphnia magna and Ceriodaphnia dubia) and for one fish species (Pimephales promelas). Mean LC50 values to C. dubia, D. magna, and P. promela were 1.12, 2.52, and 98.86 mg/L, respectively. C. dubia was the species most sensitive to HN2. Seven-day lethal and sublethal tests with P. promelas and C. dubia were also conducted. In chronic tests, fathead minnow growth was significantly reduced by 2.50 mg/L HN2, while C. dubia reproduction was significantly affected by 7.81 mug/L HN2. These adverse effects on aquatic organisms caused by lower-level concentrations of HN2 indicate that a possible aquatic ecosystem disaster could occur either after a chemical spill or during chemical warfare.     

Comparative toxicity of cadmium, zinc, and mixtures of cadmium and zinc to daphnids

Investigations were conducted to determine acute (48-h) effects of cadmium and zinc presented individually and in combination on Ceriodaphnia dubia, Daphnia magna, Daphnia ambigua, and Daphnia pulex. Toxicity tests were conducted with single metals to determine lethal effects concentrations (lethal concentrations predicted for a given percent [x] of a population, LCx value). These were used to derive metal combinations that spanned a range of effects and included mixtures of LC15, LC50, and LC85 values calculated for each metal and species. In single-metal tests, 48-h LC50 values ranged from 0.09 to 0.9 micromol/L and 4 to 12.54 micromol/L for cadmium and zinc, respectively. For each metal, D. magna was most tolerant and showed a different pattern of response from all others as determined by slope of concentration-response curves. In the combined metal treatments, all daphnids showed a similar pattern of response when LC15 concentrations were combined. This trend continued with few exceptions when LC15 concentrations of cadmium were combined with LC50 or LC85 values for zinc. However, when this treatment was reversed (LC15, zinc + LC50 or LC85, cadmium), responses of all species except D. magna indicated less-than-additive effects. For C. dubia, a near complete reduction in toxicity was observed when the LC15 for zinc was combined with LC85 for cadmium. Multimetal tests with D. magna did not differ from additive. Collectively, these studies suggest that D. magna may not be representative of other cladocerans.     

Evidence of pesticide impacts in the Santa Maria River watershed, California, USA

The Santa Maria River provides significant freshwater and coastal habitat in a semiarid region of central California, USA. We conducted a water and sediment quality assessment consisting of chemical analyses, toxicity tests, toxicity identification evaluations, and macroinvertebrate bioassessments of samples from six stations collected during four surveys conducted between July 2002 and May 2003. Santa Maria River water samples collected downstream of Orcutt Creek (Santa Maria, Santa Barbara County, CA, USA), which conveys agriculture drain water, were acutely toxic to cladocera (Ceriodaphnia dubia), as were samples from Orcutt Creek. Toxicity identification evaluations (TIEs) suggested that toxicity to C. dubia in Orcutt Creek and the Santa Maria River was due to chlorpyrifos. Sediments from these two stations also were acutely toxic to the amphipod Hyalella azteca, a resident invertebrate. The TIEs conducted on sediment suggested that toxicity to amphipods, in part, was due to organophosphate pesticides. Concentrations of chlorpyrifos in pore water sometimes exceeded the 10-d median lethal concentration for H. azteca. Additional TIE and chemical evidence suggested sediment toxicity also partly could be due to pyrethroid pesticides. Relative to an upstream reference station, macroinvertebrate community structure was impacted in Orcutt Creek and in the Santa Maria River downstream of the Creek input. This study suggests that pesticide pollution likely is the cause of ecological damage in the Santa Maria River.     

Toxicity and metal speciation in acid mine drainage treated by passive bioreactors

Sulfate-reducing passive bioreactors treat acid mine drainage (AMD) by increasing its pH and alkalinity and by removing metals as metal sulfide precipitates. In addition to discharge limits based on physicochemical parameters, however, treated effluent is required to be nontoxic. Acute and sublethal toxicity was assessed for effluent from 3.5-L column bioreactors filled with mixtures of natural organic carbon sources and operated at different hydraulic retention times (HRTs) for the treatment of a highly contaminated AMD. Effluent was first tested for acute (Daphnia magna and Oncorhynchus mykiss) and sublethal (Pseudokirchneriella subcapitata, Ceriodaphnia dubia, and Lemna minor) toxicity. Acute toxicity was observed for D. magna, and a toxicity identification evaluation (TIE) procedure was then performed to identify potential toxicants. Finally, metal speciation in the effluent was determined using ultrafiltration and geochemical modeling for the interpretation of the toxicity results. The 10-d HRT effluent was nonacutely lethal for O. mykiss but acutely lethal for D. magna. The toxicity to D. magna, however, was removed by 2 h of aeration, and the TIE procedure suggested iron as a cause of toxicity. Sublethal toxicity of the 10-d HRT effluent was observed for all test species, but it was reduced compared to the raw AMD and to a 7.3-d HRT effluent. Data regarding metal speciation indicated instability of both effluents during aeration and were consistent with the toxicity being caused by iron. Column bioreactors in operation for more than nine months efficiently improved the physicochemical quality of highly contaminated AMD at different HRTs. The present study, however, indicated that design of passive treatment should include sufficient HRT and posttreatment aeration to meet acute toxicity requirements.     

Acute enantioselective toxicity of fipronil and its desulfinyl photoproduct to Ceriodaphnia dubia

Fipronil is a phenylpyrazole insecticide increasingly used in applications such as rice culture, turf grass management, and residential pest control, with a high probability to contaminate aquatic environments. As a chiral pesticide, fipronil is released to the environment as a racemic mixture (equal amounts of optical isomers called enantiomers). Enantiomers can have different toxicological and biological activity; however, information on these differences, which is necessary for accurate risk assessment of chiral pesticides, is limited. Here we examine the acute toxicity of fipronil enantiomers, the racemate, and its photoproduct (desulfinyl fipronil) to Ceriodaphnia dubia. The 48-h median lethal concentration (LC50) values based on measured concentrations of each compound indicate the (+) enantiomer (LC50 = 10.3 +/- 1.1 microg/L, mean +/- standard error [SE]) was significantly more toxic to C. dubia than either the (-) enantiomer (LC50 = 31.9 +/- 2.2 microg/L) or racemate (LC50 = 17.7 +/- 1.3 microg/L). To account for any potential loss of fipronil through photolysis, tests were performed under light (fluorescent) and dark exposure conditions, and no significant differences in toxicity were observed. Desulfinyl fipronil, the major photodegradation product, which is not chiral, was detected at < 1% of each parent compound in test solutions after 48 h. Separate toxicity tests with desulfinyl fipronil found a > 20-fold higher LC50 (355 +/- 9.3 microg/L) compared to the fipronil racemate, suggesting lower adverse effects to C. dubia as a result of fipronil photolysis. The present results suggest selection of the (-) enantiomer in fipronil production for lower impacts to C. dubia; however, the consistency and relevancy of fipronil's enantiomer-specific activity at both acute and chronic levels of concern to additional target and nontarget species needs further consideration.     

Marine sediment toxicity identification evaluation methods for the anionic metals arsenic and chromium

Marine sediments accumulate a variety of contaminants and, in some cases, demonstrate toxicity because of this contamination. Toxicity identification evaluation (TIE) methods provide tools for identifying the toxic chemicals causing sediment toxicity. Currently, whole-sediment TIE methods are not available for anionic metals like arsenic and chromium. In the present paper, we describe two new anion-exchange resins used in the development of whole-sediment TIE methods for arsenic and chromium. Resins were shown to reduce whole-sediment toxicity and overlying water concentrations of the anionic metals. Sediment toxicity, expressed as the median lethal concentration, was reduced by a factor of two to a factor of nearly six between amended sediment treatments containing resin and those without resin. Aqueous concentrations of arsenic and chromium in the toxicity exposures decreased to less than the detection limits or to concentrations much lower than those measured in treatments without resin. Interference studies indicated that the anion-exchange resins had no significant effect on concentrations of the representative pesticide endosulfan and minimal effects on concentrations of ammonia. However, the anion-exchange resins did significantly reduce the concentrations of a selection of cationic metals (Cd, Cu, Ni, Pb, and Zn). These data demonstrate the utility of anion-exchange resins for determining the contribution of arsenic and chromium to whole-sediment toxicity. The present results also indicate the importance of using TIE methods in a formal TIE structure to ensure that results are not misinterpreted. These methods should be useful in the performance of marine whole-sediment TIEs.     

Joint acute toxicity of diazinon and copper to Ceriodaphnia dubia

Diazinon and copper are two contaminants that are widely found in urban streams and in municipal wastewater effluents. Because these contaminants may be found concurrently, the potential for their joint toxicity is of interest, particularly with regard to toxicity testing of wastewater effluents and the ecological implications of simultaneous exposures in urban streams. Although interactions between metals are well studied, relatively little is known about interactions between metals and organophosphate compounds such as diazinon. In this study, the interaction between copper and diazinon was evaluated using cladoceran (Ceriodaphnia dubia) in 48-h static tests within laboratory water. Using toxic units derived from concurrently established 48-h median lethal concentration values (LC50) of test organisms of each individual toxicant, the effects of the mixture of copper and diazinon on the survival of C. dubia were shown to be generally nonconcentration additive (LC50 significantly greater than one toxic unit). However, evaluation of the dose-response relationship across the entire range of effect levels revealed that the mortality induced by the mixture of copper and diazinon supported concentration additivity at higher effect levels.     

Ecotoxicologic impacts of agricultural drain water in the Salinas River, California, USA

The Salinas River is the largest of the three rivers that drain into the Monterey Bay National Marine Sanctuary in central California (USA). Large areas of this watershed are cultivated year-round in row crops, and previous laboratory studies have demonstrated that acute toxicity of agricultural drain water to Ceriodaphnia dubia is caused by the organophosphate (OP) pesticides chlorpyrifos and diazinon. We investigated chemical contamination and toxicity in waters and sediments in the river downstream of an agricultural drain water input. Ecological impacts of drain water were investigated by using bioassessments of macroinvertebrate community structure. Toxicity identification evaluations were used to characterize chemicals responsible for toxicity. Salinas River water downstream of the agricultural drain was acutely toxic to the cladoceran Ceriodaphnia dubia, and toxicity to C. dubia was highly correlated with combined toxic units (TUs) of chlorpyrifos and diazinon. Laboratory tests were used to demonstrate that sediments in this system were acutely toxic to the amphipod Hyalella azteca, a resident invertebrate. Toxicity identification evaluations (TIEs) conducted on sediment pore water suggested that toxicity to amphipods was due in part to OP pesticides; concentrations of chlorpyrifos in pore water sometimes exceeded the 10-d mean lethal concentration (LC50) for H. azteca. Potentiation of toxicity with addition of the metabolic inhibitor piperonyl butoxide suggested that sediment toxicity also was due to other non-metabolically activated compounds. Macroinvertebrate community structure was highly impacted downstream of the agricultural drain input, and a number of macroinvertebrate community metrics were negatively correlated with combined TUs of chlorpyrifos and diazinon, as well as turbidity associated with the drain water. Some macroinvertebrate metrics were also correlated with bank vegetation cover. This study suggests that pesticide pollution is the likely cause of ecological damage in the Salinas River, and this factor may interact with other stressors associated with agricultural drain water to impact the macroinvertebrate community in the system.     

Acute toxicity of copper, ammonia, and chlorine to glochidia and juveniles of freshwater mussels (Unionidae)

The objective of the present study was to determine acute toxicity of copper, ammonia, or chlorine to larval (glochidia) and juvenile mussels using the recently published American Society for Testing and Materials (ASTM) Standard guide for conducting laboratory toxicity tests with freshwater mussels. Toxicity tests were conducted with glochidia (24- to 48-h exposures) and juveniles (96-h exposures) of up to 11 mussel species in reconstituted ASTM hard water using copper, ammonia, or chlorine as a toxicant. Copper and ammonia tests also were conducted with five commonly tested species, including cladocerans (Daphnia magna and Ceriodaphnia dubia; 48-h exposures), amphipod (Hyalella azteca; 48-h exposures), rainbow trout (Oncorhynchus mykiss; 96-h exposures), and fathead minnow (Pimephales promelas; 96-h exposures). Median effective concentrations (EC50s) for commonly tested species were >58 microg Cu/L (except 15 microg Cu/L for C. dubia) and >13 mg total ammonia N/L, whereas the EC50s for mussels in most cases were <45 microg Cu/L or <12 mg N/L and were often at or below the final acute values (FAVs) used to derive the U.S. Environmental Protection Agency 1996 acute water quality criterion (WQC) for copper and 1999 acute WQC for ammonia. However, the chlorine EC50s for mussels generally were >40 microg/L and above the FAV in the WQC for chlorine. The results indicate that the early life stages of mussels generally were more sensitive to copper and ammonia than other organisms and that, including mussel toxicity data in a revision to the WQC, would lower the WQC for copper or ammonia. Furthermore, including additional mussel data in 2007 WQC for copper based on biotic ligand model would further lower the WQC.