Dubia Survival Research Articles

Long-term toxicity of chlorpromazine, diclofenac and two lanthanides on three generations of Ceriodaphnia dubia.

Amultigenerational study on Ceriodaphnia dubia was carried out by exposing three subsequent generations to pharmaceuticals chlorpromazine (CPZ) and diclofenac (DCF), and two lanthanide chlorides, gadolinium as GdCl3 and europium as EuCl3. As the treatments, environmentally relevant concentrations were chosen (0.001, 0.01 and 0.1 mg/L for CPZ; 0.1, 1 and 10 mg/L for DCF; 0.425, 4.25 and 42.5 µg/L for Gd and 0.41, 4.1 and 41 µg/L for Eu). Survival, population growth and reproduction success were evaluated at 21 and 30 days of exposure, and the whole observation period lasted 40 days. The least sensitive to all selected substances was the first daphnid generation (F1). Within 21-day exposure, no significant effects of the psychotropic drug CPZ on C. dubia survival were observed in generations F1-F3. The anti-inflammatory drug DCF did not affect survival in the F1 generation; however, it significantly reduced survival in the F3 generation at 1-10 mg/L. Both lanthanides did not affect survival in the F1 and F2 generations of C. dubia but considerably decreased survival in the F3 at 4-42 µg/L. Both pharmaceuticals stimulated the reproduction of C. dubia in the F1 generation, while inhibition occurred at the highest tested concentrations in generations F2 and F3. The inhibitory effect on the reproductive success of lanthanides in the F2 generation resembled that for CPZ but not for DCF. The dynamics of adverse effects during the 21-30-day period revealed that despite increased mortality in the controls (up to 30%), concentrations used in the study minified, in most instances, the survival and aggravated population growth and reproduction success of C. dubia. Our data suggest that C. dubia as a test organism can be used for 21 days in multigenerational investigations, especially when testing close to environmental concentrations. In this respect, the standard C. dubia chronic toxicity assay seems limited since prolonged observations and several generations of daphnids are required to obtain reliable information for the risk assessment of potentially aggressive chemicals.

Complex mixture toxicology: Evaluation of toxicity to freshwater aquatic receptors from biodegradation metabolites in groundwater at a crude oil release site, recent analogous results from other authors, and implications for risk management

Aquatic toxicity posed by the complex mixture of biodegradation metabolites and related oxygen-containing organic compounds (OCOCs) in groundwater at typical petroleum release sites is of concern to regulatory agencies; several are using results from laboratory studies in older literature that are not appropriate analogs for risk management. Recent field studies from typical sites and natural groundwater should be utilized. In this study, OCOCs downgradient of the biodegrading crude oil release at the USGS Bemidji site were tested for freshwater aquatic toxicity using unaltered whole groundwater samples. This type of testing is optimal because the entire mixture of OCOCs present is tested directly and assessment is not affected by analytical limitations. Ceriodaphnia dubia and Pimephales promelas were tested for toxicity using USEPA Methods 1002 and 1000, which estimate chronic toxicity. OCOCs in representative samples up to the maximum concentration tested of 1710 ug/L Total Petroleum Hydrocarbons (TPH) (nC10 to nC40; without silica gel cleanup) did not result in effects relative to the lab control for C. dubia survival, or for P. promelas survival or growth; and did not result in effects above background for C. dubia reproduction. This is consistent with findings using the same testing methods and species on samples from 14 biodegrading fuel release sites: OCOCs did not cause increased toxicity relative to background at a maximum tested concentration of 1800 ug/L TPH (nC10 to nC28). Based on their toxicity testing using the same species and USEPA methods on groundwater from a biodegrading diesel release site, Washington Department of Ecology recently set a freshwater screening level for OCOCs at 3000 ug/L TPH (“Weathered DRO”). These studies indicate that, in the absence of dissolved hydrocarbons, OCOCs in groundwater from typical biodegrading fuel or crude oil releases are not toxic to C. dubia or P. promelas at typical concentrations.

Survival and Reproductive Effects in the Aquatic Invertebrate Ceriodaphnia dubia Exposed to Uranium Spiked Site Water Collected from Two Creeks in the Yukon, Canada.

This study evaluates aqueous uranium (U) toxicity in Ceriodaphnia dubia exposed to surface water collected from two creeks located in U-rich areas of Yukon, Canada. Water for toxicity testing was collected at two times of the year to represent water quality characteristics generally observed during open-water (high flows) and winter baseflow water (low flows) seasons. Collected water was transferred to the toxicological laboratory and spiked with U to achieve nominal concentrations of 50, 150, 350, 500, 650, 800, and 1000µgU/L. Toxicity endpoints included lethal concentrations (LC50) for survival, in addition to no observed effect concentration (NOEC) and lowest observed effect concentration (LOEC) for reproduction. All derived toxicity endpoints were significantly higher than applicable Canadian water-quality guidelines for U (15μg/L [Chronic] and 33μg/L [Acute]). No effects on C. dubia survival were observed at LC50 concentrations > 799μgU/L. Derived NOEC (381μgU/L) and LOEC (524μgU/L) values also were significantly above chronic water quality guidelines. The differences noted in the toxicity response between seasons were mainly due to the presence of toxicity ameliorating factors for U (i.e., dissolved organic carbon). These results highlight the high conservatism in applicable water-quality guidelines and the crucial need to consider site-specific water characteristics when deriving environmentally relevant, yet protective thresholds for uranium in aquatic environments.

Toxicity of Aluminum to Ceriodaphnia dubia in Low-Hardness Waters as Affected by Natural Dissolved Organic Matter.

We conducted a series of 7-d toxicity tests with Ceriodaphnia dubia in dilutions of low-hardness natural waters, which contained dissolved organic carbon (DOC) concentrations up to 10 mg/L. Stream waters were mixed with well water to achieve 2 target hardness levels (20 and 35 mg/L) and 4 DOC concentrations. Tests with aluminum (Al)-spiked waters were conducted in a controlled CO2 atmosphere to maintain the pH at a range of 6.0 to 6.5. The results were used to estimate effect concentrations for survival and reproduction, expressed as total (unfiltered) Al concentrations. There were small differences in total-Al thresholds between waters with 20 and 35 mg/L hardness, but effect concentrations for C. dubia survival (median lethal concentrations) and reproduction (effect concentrations, 20%) increased log-linearly with increasing DOC concentrations in the range, 0.3 to 6 mg/L. Slopes of these regressions were similar to slopes from data used to revise the US Environmental Protection Agency water quality criterion for Al, but toxic effects in the present study occurred at total-Al concentrations 8- to 10-fold greater than toxicity values used for criteria development. This difference probably reflects the long equilibration (aging) times of Al test waters used in the present study (up to 192 h) compared with short (3-h) equilibration times in other studies used for criteria development. These results confirm the importance of DOC as a control on Al toxicity in low-hardness waters, but they also demonstrate that total-Al concentrations are not predictive of Al toxicity, except under defined water quality (pH, hardness, DOC) and exposure conditions (e.g., aging of test waters). Environ Toxicol Chem 2019;38:2121-2127. Published 2019 Wiley Periodicals, Inc. on behalf of SETAC. This article is a US government work, and as such, is in the public domain in the United States of America.

Treatment of oil sands process-affected waters using a pilot-scale hybrid constructed wetland

Constructed wetland treatment systems (CWTSs) could provide a passive, low-energy strategy for mitigating risks associated with oil sands process-affected waters (OSPWs). Due to the large volumes (over 975 million m3), heterogeneous composition, and acute and chronic toxicity of OSPW, passive and efficient treatment to decrease risks to biota will be necessary once operators obtain regulatory permission to discharge into aquatic receiving systems. The research objective was to design, assemble, and measure performance of a pilot-scale hybrid CWTS for treatment of OSPW. Constituents of concern (COCs) identified in OSPW included NAs, oil and grease, As, B, Cu, Pb, and Zn. Oxidizing conditions (net sediment redox > −50 mV) were promoted to allow aerobic degradation of organic constituents, and co-precipitation of arsenic with iron oxyhydroxides. Treatment of Cu, Pb, and Zn was targeted through precipitation with sulfides in reducing “micro-environments” in wetland sediments. Solar photocatalytic reactors (hybrid components) were used to remove recalcitrant organics. Performance was assessed using rates and extents of removal of COCs and changes in toxicity as indicated by Ceriodaphnia dubia. Mean total naphthenic acid fraction compound concentrations decreased from approximately 43 mg/L in untreated OSPW to 10 mg/L following a 16-d retention time in the hybrid CWTS. Mean As and Zn concentrations decreased from 0.026 mg/L and 0.129 mg/L in untreated OSPW to 0.011–0.014 mg/L and 0.052–0.062 mg/L in wetland outflows, respectively. Cu and Pb mass decreased by 13–26% in the CWTS; however, evaporative concentration masked removal (in terms of total metal concentrations). Toxicity (in terms of C. dubia survival and reproduction) of OSPW was eliminated following treatment. Results demonstrate that hybrid CWTSs can effectively degrade NAs and alleviate toxicity associated with metals and organics in OSPW.

Pesticide Toxicity Index—A tool for assessing potential toxicity of pesticide mixtures to freshwater aquatic organisms

Pesticide mixtures are common in streams with agricultural or urban influence in the watershed. The Pesticide Toxicity Index (PTI) is a screening tool to assess potential aquatic toxicity of complex pesticide mixtures by combining measures of pesticide exposure and acute toxicity in an additive toxic-unit model. The PTI is determined separately for fish, cladocerans, and benthic invertebrates. This study expands the number of pesticides and degradates included in previous editions of the PTI from 124 to 492 pesticides and degradates, and includes two types of PTI for use in different applications, depending on study objectives. The Median-PTI was calculated from median toxicity values for individual pesticides, so is robust to outliers and is appropriate for comparing relative potential toxicity among samples, sites, or pesticides. The Sensitive-PTI uses the 5th percentile of available toxicity values, so is a more sensitive screening-level indicator of potential toxicity. PTI predictions of toxicity in environmental samples were tested using data aggregated from published field studies that measured pesticide concentrations and toxicity to Ceriodaphnia dubia in ambient stream water. C. dubia survival was reduced to ≤50% of controls in 44% of samples with Median-PTI values of 0.1–1, and to 0% in 96% of samples with Median-PTI values >1. The PTI is a relative, but quantitative, indicator of potential toxicity that can be used to evaluate relationships between pesticide exposure and biological condition.

Variation in toxicity response of Ceriodaphnia dubia to Athabasca oil sands coke leachates

Coke from the Athabasca (Alberta, Canada) oil sands operations may someday be integrated into reclamation landscapes. It is hypothesized that the metals associated with the solid coke may leach into the surrounding environment. Therefore, the main objectives of this study were to characterize the toxicity and chemistry of coke leachates collected from two field lysimeters (i.e. shallow lysimeter and deep lysimeter) over a period of 20 months, as well as from other oil sands coke storage sites. In addition, a batch renewal leaching of coke was conducted to examine the rate of metals release. Chronic toxicity of key metals (e.g. Al, Mn, Ni and V) found in lysimeter coke leachate was evaluated separately. Toxicity test results revealed that whole coke leachates (100% v/v) were acutely toxic to Ceriodaphnia dubia; the 7-day LC50 values were always <25% v/v coke leachate. The deep lysimeter leachate was generally more toxic than the shallow lysimeter leachate, likely because of significantly higher concentrations of vanadium (V) found in the deep lysimeter leachate at all sampling times. Vanadium concentrations were higher than all other metals found in the leachate from both lysimeters, and in the batch renewal leaching study. Furthermore, V found in leachates collected from other oil sands field sites showed a concentration–response relationship with C. dubia survival. Mass balance calculations indicated that 94–98% of potentially leachable V fraction was still present in the coke from two field lysimeters. Evidence gathered from these assessments, including toxic unit (TU) calculations for the elements of concern, suggests that V was the likely cause of toxicity of the deep lysimeter leachate, whereas in the shallow lysimeter leachate both Ni and V could be responsible for the observed toxicity.

Comparison between four and seven-day Ceriodaphnia dubia survival and reproduction test protocols using oil refinery effluent samples

The aim of this study was to compare the 7-day Ceriodaphnia dubia survival and reproduction test with a 4 day test to evaluate the toxicity of oil refinery effluents. Both shown identical NOECs with three of 6 tested samples. With one of the tested samples, the 4-day NOEC was one tested-concentration lower, and with the remaining two samples, it was one tested-concentration higher than those obtained using the 7-day protocol. Then results suggested that 4 and 7-day protocols were comparable to detect toxic effects.

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.

Assessment of Diazinon Toxicity in Sediment and Water of Constructed Wetlands Using Deployed Corbicula fluminea and Laboratory Testing

Constructed wetlands for mitigation of nonpoint agricultural runoff have been assessed for their ability to decrease potential toxicity from associated contaminants. After a simulated runoff event, constructed wetlands positioned in series were used to measure the effects of the organophosphate insecticide diazinon. Water, sediment, and plant samples from five sites were analyzed for diazinon concentrations from 0.5 hours to 26 days; peak concentrations were measured in sediment after 0.5 hours (268.7 microg/kg) and in water and plant tissue after 3 hours (121.71 microg/L and 300.7 microg/kg, respectively). Cholinesterase activity and changes in shell growth were measured from Corbicula fluminea deployed at corresponding sites. Water collected after 9 hours from all wetland sites contained diazinon concentrations sufficient to cause toxicity to Ceriodaphnia dubia, but not to Pimephales promelas. C. dubia survival was decreased in water sampled through 7 days from the site nearest runoff introduction, whereas C. fluminea deployed at this same site experienced 100% mortality after 26 days. Clams from lower sites survived wetland conditions, but growth and ChE activity were significantly decreased lower than that of clams from a control site. C. dubia exposed to water from these sites continued to have decreased survival throughout the 26-day sampling. Sediment sampled from 48 hours through 14 days at the lowest wetland site decreased the laboratory survival of Chironomus dilutus, and sediment from upper sites elicited an effect only on day 26. Although wetland concentrations of aqueous diazinon were decreased lower than toxic thresholds after 26 days, decreased ChE activity in deployed clams provided evidence of residual diazinon effects to deployed organisms.

Interaction of chemical cues from fish tissues and organophosphorous pesticides on Ceriodaphnia dubia survival

Cladocera are frequently used as test organisms for assessing chemical and effluent toxicity and have been shown to respond to stimuli and cues from potential predators. In this study, the interactive effects of visual and chemical cues of fish and two organophosphorous pesticides on survival of Ceriodaphnia dubia were examined. A significant chemical cue (homogenized Pimephales promelas) and malathion interaction was observed on C. dubia survival ( P = 0.006). Chemical cue and 2.82 μg/L malathion resulted in a 76.0% reduction in survival compared to malathion alone ( P < 0.01). Furthermore, potentiation of malathion toxicity varied based on the source of chemical cues (i.e., epithelial or whole body). It is unclear in this study whether these chemical cues elicited a predation-related stress in C. dubia. Future research should examine the mechanism of this interaction and determine what role, if any, stress responses by C. dubia might play in the interaction.

A biomonitoring approach to aquaculture effluent characterization in channel catfish fingerling production

The channel catfish ( Ictalurus punctatus) industry has come under increased scrutiny because of potential environmental impact from their discharge. Physicochemical analyses have been used to characterize these effluents and their potential environmental impacts. In this study, the relationship between physicochemical characterization and bioassessment was examined for effluents from 12 commercial channel catfish fingerling ponds, sampled September 1999 through August 2001. On each sampling date, effluent samples were collected by opening the drain valve for 1 h. Biomonitoring and physicochemical analyses were conducted on the sample collected immediately after opening the drain (“initial sample”) and the final sample collected after 1 h (“final sample”). Greater incidence of toxicity responses measured as % of total tests was observed in standard test organism exposures in initial samples than in final samples of monitored hourly discharges. In acute 48-h static non-renewal tests, Pimephales promelas experienced 20.5% significant ( P<0.05) survival reductions in initial effluent exposures and only 2.6% in final effluent exposures from 39 tested effluents. Ceriodaphnia dubia survival in chronic 7-day static-renewal tests was significantly ( P<0.05) reduced in 12.8% of 39 initial effluent exposures while there were no significant responses in final effluent exposures. Likewise, reproductive responses of C. dubia were also significantly ( P<0.05) reduced in 35.9% of initial exposures and 15.4% of final effluent exposures from 39 tested effluents. Biomonitoring of fingerling pond discharges was used to evaluate effluent quality by measuring standard organism responses. While reduced effluent quality was of relative short duration, as is typical of the industry, this multidimensional approach, utilizing biomonitoring, was used to identify risk posed by critical concentrations of whole effluents to receiving stream communities.

Toxicity effects of γ-irradiated wastewater effluents

Conventional wastewater disinfection is typically accomplished via chlorination, ozonation or ultraviolet (UV) irradiation. For each of these disinfectants, changes in the composition of the disinfected waters are known to occur and have been linked to changes in the toxicity responses of the disinfected effluent. The toxicity responses of wastewater effluent samples exposed to an alternative disinfectant, gamma ( γ) radiation, have been studied and compared with the responses to chlorinated (with dechlorination) and undisinfected municipal wastewater effluent samples. Predisinfection samples were taken from six wastewater treatment plants. Multiple samples from each facility were split and subsamples were exposed to γ-irradiation, as well as chlorination/dechlorination in batch reactors. The disinfected and undisinfected subsamples were then assayed for toxicity using the Ceriodaphnia dubia chronic toxicity test. Wastewater disinfectant doses were sufficient to meet coliform limitations for effluent quality in all cases; furthermore, the batch disinfectant exposure protocols accomplished extents of coliform inactivation that were comparable to those observed in the disinfection unit operations at the full-scale facilities from which the samples were collected. Analysis of data from these assays showed that γ-irradiation induced significantly less toxicity in terms of C. dubia survival and reproduction than chlorination/dechlorination. Toxicity in the γ-irradiated effluent either decreased or was unchanged as compared to an undisinfected sample; effluent samples subjected to chlorination/dechlorination often showed a statistically significant increase in toxicity as compared to the undisinfected samples and the γ-irradiated samples.

Effects of disinfectants on wastewater effluent toxicity

Wastewater disinfection is most commonly achieved by halogenation, ozonation or ultraviolet (UV) irradiation. All of these processes are known to be capable of inducing chemical changes among non-microbial aqueous constituents, which can lead to changes in effluent toxicity behavior. Undiluted effluent samples from seven wastewater treatment facilities were exposed to commonly-applied disinfectants (chlorination/dechlorination, ozonation and UV irradiation) and assayed for their toxicity behavior; Ceriodaphnia dubia survival and reproduction were used as measures of chronic toxicity. The results of these assays confirmed the ability of all the disinfectants to alter toxicity response behavior. The toxicity responses demonstrated site-specificity and strong temporal variations. In general, when undisinfected effluent did not display toxicity, no toxicity was observed following any of the disinfection procedures; when toxicity was displayed in the undisinfected effluent, all disinfectants demonstrated the ability to alter toxicity, in most cases resulting in an increase. The changes in toxicological response attributable to disinfectant exposure followed the trend: chlorination/dechlorination > ozonation > UV irradiation, but substantial variations from this trend were evident in individual samples.

In situ toxicity evaluations of turbidity and photoinduction of polycyclic aromatic hydrocarbons

AbstractPolycyclic aromatic hydrocarbons (PAHs) are prevalent pollutants in the aquatic environment that can cause a wide range of toxic effects. Earlier studies have shown that toxicity of PAHs can be enhanced by ultraviolet (UV) radiation. In situ and laboratory exposures with Ceriodaphnia dubia were used to evaluate photoinduced toxicity of PAHs in wet‐weather runoff and in turbid conditions. Exposure to UV increased the toxicity of PAH‐contaminated sediment to C. dubia. Toxicity was removed when UV wavelengths did not penetrate the water column to the exposed organisms. A significant correlation was observed between in situ C. dubia survival and turbidity when organisms were exposed to sunlight. Stormwater runoff samples exhibited an increase in chronic toxicity (reproduction) to C. dubia when exposed to UV wavelengths as compared to C. dubia not exposed to UV wavelengths. Toxicity was reduced significantly in the presence of UV radiation when the organic fraction of stormwater runoff was removed. The PAHs are bound to the sediment and resuspended into the water column once the sediment is disturbed (e.g., during a storm). The in situ and laboratory results showed that photoinduced toxicity occurred frequently during low flow conditions and wet weather runoff and was reduced in turbid conditions.

Toxicity of arsenic, molybdenum and selenium combinations to Ceriodaphnia dubia

AbstractPrevious research done on the effects of contaminant mixtures has been evaluated primarily by using acute exposures. While this was an important initial step, characterizing the effects of chronic exposures of these mixtures is more environmentally pragmatic. This study examined the sublethal interactive effects of arsenic (As), molybdenum (Mo), and selenium (Se) on Ceriodaphnia dubia using the three‐brood static renewal toxicity test. A complete factorial design experiment using four levels (zero, IC12.5, IC25, and IC50 values) of each metal was performed to investigate the binary and tertiary interactions of these metals on C. dubia survival and fecundity. Results indicate three‐way interactive effects in survival and fecundity with the strongest effect exhibited by Se. Molybdenum and As in binary combinations appear to be strongly antagonistic in their effects on C. dubia, even at their respective IC50 concentrations. However, generally the addition of Se to As‐Mo mixtures significantly reduced survival and reproduction. The IC50 concentrations of either Mo or Se significantly reduced fecundity in all binary and tertiary mixtures. All tertiary metal mixtures, except the combination of the IC12.5 concentrations of each metal, significantly reduced C. dubia fecundity.

CHEMICAL CHARACTERIZATION AND TOXICOLOGICAL TESTING OF WINDROW COMPOSTS FROM EXPLOSIVES-CONTAMINATED SEDIMENTS

Aerated and nonaerated windrow composts of explosives-contaminated sediments at the Umatilla Army Depot Activity (UMDA, Hermiston, OR) were characterized chemically and toxicologically as a function of composting time. The concentrations of explosives in organic solvent extracts of the composts and in the aqueous leachates of the composts, the bacterial mutagenicity of organic solvent extracts from the composts, and the toxicity of aqueous leachates from the composts to Ceriodaphnia dubia all declined rapidly (<15 d) with composting. The nonaerated windrow method of composting was slightly more efficient than was the aerated windrow method for reducing explosives concentrations in the composts (TNT, 99.9%; RDX, >99.7%; HMX, 98.5%) and in their leachates (>99.6%, >98.8%, and >97.5%, respectively). Extractable mutagenicity declined 99.7 and 97.9%, respectively, for strains TA-98 and TA-100 (without S-9 metabolic activation) in the nonaerated compost. The two types (aerated and nonaerated) of windrow composts had about the same level of efficiency in lowering leachable toxicity (by 92% and 87%, based on reductions in C. dubia survival and fecundity, respectively). Thus, windrow composting appeared to be at least as effective as static-pile and mechanically stirred composting evaluated previously. Windrow composting also appeared to be somewhat more effective for HMX transformation.

Chemical characterization and toxicological testing of windrow composts from explosives‐contaminated sediments

AbstractAerated and nonaerated windrow composts of explosives‐contaminated sediments at the Umatilla Army Depot Activity (UMDA, Hermiston, OR) were characterized chemically and toxicologically as a function of composting time. The concentrations of explosives in organic solvent extracts of the composts and in the aqueous leachates of the composts, the bacterial mutagenicity of organic solvent extracts from the composts, and the toxicity of aqueous leachates from the composts to Ceriodaphnia dubia all declined rapidly (&lt;15 d) with composting. The nonaerated windrow method of composting was slightly more efficient than was the aerated windrow method for reducing explosives concentrations in the composts (TNT, 99.9%; RDX, &gt;99.7%; HMX, 98.5%) and in their leachates (&gt;99.6%, &gt;98.8%, and &gt;97.5%, respectively). Extractable mutagenicity declined 99.7 and 97.9%, respectively, for strains TA‐98 and TA‐100 (without S‐9 metabolic activation) in the nonaerated compost. The two types (aerated and nonaerated) of windrow composts had about the same level of efficiency in lowering leachable toxicity (by 92% and 87%, based on reductions in C. dubia survival and fecundity, respectively). Thus, windrow composting appeared to be at least as effective as static‐pile and mechanically stirred composting evaluated previously. Windrow composting also appeared to be somewhat more effective for HMX transformation.

Variability in the performance of the 7-dCeriodaphnia dubiasurvival and reproduction test: An intra- and interlaboratory study

The U.S. Environmental Protection Agency (EPA) has developed a 7-day Ceriodaphnia dubia survival and reproduction test for measuring the toxicity of effluents. This study evaluated the ease of performance and the intra- and interlaboratory variability of this 7-d test, using two reference toxicants (sodium chloride and potassium dichromate), two pulp and paper effluents, and two utility effluents Eleven different laboratories, representing academia, private industry, contractors, and the state EPA and federal EPA, participated in the study. The reference toxicants were tested twice during two separate test periods, and each industrial effluent was tested once. Using the EPA's criteria for a successful test (®80% survival and ® 15 young per female in controls), 56% of the 116 planned tests were completed as valid tests. Most tests were invalid because the laboratories were unable to initiate the tests successfully or because control survival was <80%. Seventy-eight percent of the tests that were initiated were successfully completed. Reproduction no-observed-effect-concentration (NOEC) values were generally somewhat lower than those for survival but had greater variability than survival NOEC values. The interlaboratory variability of the survival (LC50) and reproduction (IC50) results, expressed as the C V., ranged between 29.8 and 30.8% and between 28.9 and 39.0%, respectively. The study demonstrated that about half (56%) of the laboratories participating in the study were able to routinely complete the test successfully. Some of the laboratories experienced with other effluent toxicity tests were less prepared to complete this test successfully. Overall, the variability of the 7-d Ceriodaphnia tests that were completed was similar to the variability observed with other toxicity tests and with analytical chemistry measurements of environmental samples.

Effects of environmental and experimental design factors on culturing and toxicity testing ofCeriodaphnia dubia

The U S. Environmental Protection Agency (EPA) has developed a 7-d toxicity test to evaluate effects of effluents on Ceriodaphnia dubia survival and reproduction. This study evaluated effects of laboratory culture and test procedures on Ceriodaphnia dubia survival and reproduction Parameters such as temperature, food concentration, beaker size, solution-renewal frequency, light quality, illumination, photoperiod, water type, and test organism age were evaluated to determine how these culture and test parameters affected individual culturing success and acceptability and reproducibility of toxicity test results. Test parameters proposed by the EPA were evaluated under controlled laboratory conditions by varying levels of individual environmental or experimental design parameters to determine an acceptable range of responses for survival and reproduction, both with and without a reference toxicant For those parameters not specified by the EPA (e.g, water hardness, light quality), commonly used ranges for those parameters were evaluated. Results provided a decision matrix of acceptable ranges for individual environmental and experimental design parameters that were used to optimize the test parameters for conducting 7-d effluent tests with Ceriodaphnia dubia Overall, of the studied test parameters, renewal frequency and photopenod were the primary factors affecting culture and toxicity test success In this study, the EPA restriction on Ceriodaphnia dubia age at test initiation was not critical, as long as all organisms were <24 h old and randomly distributed among the test concentrations