Variation in chronic nickel toxicity to Daphnia magna among Japanese river waters and performance evaluation of bioavailability models in predicting the toxicity.

Nickel (Ni) ecotoxicity is dictated by water chemistry characteristics such as pH, water hardness, and amount of dissolved organic carbon. Bioavailability models have been developed to predict Ni toxicity and validated for European, Australian, and US natural waters. In this study, chronic toxicity tests in Ni-spiked Japanese river waters were conducted on a strain of Daphnia magna to test whether the chronic toxicity differs among Japanese natural waters with different water chemistries. Based on the results of chronic Ni toxicity tests, we assessed the performance of existing D. magna bioavailability models, which were developed in artificial waters (Model 1) and calibrated in European natural waters (Model 2), in terms of the accuracy and the bias of model predictions. Furthermore, we also calibrated the two models by using toxicity test results to develop a bioavailability model for Ni chronic toxicity to the strain of D. magna in Japanese river waters. The 10%, 20%, and 50% effect concentrations (EC10, EC20, and EC50) of dissolved Ni on reproduction of the D. magna strain were within ranges from 8.1 to 44.9 µg/L, 9.0 to 57.1 µg/L, and 10.9 to 86.1 µg/L, respectively. Results indicate that differences in water chemistry among Japanese river waters influenced chronic Ni toxicity to the model organism. Model 1predicted 43% of the observed EC10, EC20, and EC50 values within a factor of 2 and 100%, 100%, and 43% within a factor of 3, respectively. Model 2 predicted 14%, 14%, and 29% of the observed EC10, EC20, and EC50 values within a factor of 2 and 43% within a factor of 3. The values of model bias based on the geometric mean of ratios of EC10, EC20 and EC50 values predicted by each of the two models and observed EC10, EC20, and EC50 values were 0.71, 0.65, and 0.62 for Model 1 and 0.27, 0.26, and 0.29 for Model 2, respectively. After calibrating two models using the results of toxicity tests, refined Model 1 predicted 71%, 57%, and 57% of observed EC10, EC20, and EC50 values within a factor of 2 and 100%, 86%, and 100% within a factor of 3; refined Model 2 predicted 71% of observed EC10, EC20, and EC50 values within a factor 2 and 100%, 86%, and 86% within a factor of 3, respectively. Our results indicate that calibrating the Ni bioavailability models in Japanese natural waters increased their predictive capacity by a factor of up to approximately five.

Modeling the Bioavailability of Nickel and Zinc to Ceriodaphnia dubia and Neocloeon triangulifer in Toxicity Tests with Natural Waters.

We studied biotic ligand model (BLM) predictions of the toxicity of nickel (Ni) and zinc (Zn) in natural waters from Illinois and Minnesota, USA, which had combinations of pH, hardness, and dissolved organic carbon (DOC) more extreme than 99.7% of waters in a nationwide database. We conducted 7-day chronic tests with Ceriodaphnia dubia and 96-hour acute and 14-day chronic tests with Neocloeon triangulifer and estimated median lethal concentrations and 20% effect concentrations for both species. Toxicity of Ni and Zn to both species differed among test waters by factors from 8 (Zn tests with C. dubia) to 35 (Zn tests with N. triangulifer). For both species and metals, tests with Minnesota waters (low pH and hardness, high DOC) showed lower toxicity than Illinois waters (high pH and high hardness, low DOC). Recalibration of the Ni BLM to be more responsive to pH-related changes improved predictions of Ni toxicity, especially for C. dubia. For the Zn BLM, we compared several input data scenarios, which generally had minor effects on model performance scores (MPS). A scenario that included inputs of modeled dissolved inorganic carbon and measured Al and Fe(III) produced the highest MPS values for tests with both C. dubia and N. triangulifer. Overall, the BLM framework successfully modeled variation in toxicity for both Zn and Ni across wide ranges of water chemistry in tests with both standard and novel test organisms. Environ Toxicol Chem 2021;40:3049-3062. © 2021 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Application of Bioavailability Models to Derive Chronic Guideline Values for Nickel in Freshwaters of Australia and New Zealand.

There has been an increased emphasis on incorporating bioavailability-based approaches into freshwater guideline value derivations for metals in the Australian and New Zealand water quality guidelines. Four bioavailability models were compared: the existing European biotic ligand model (European Union BLM) and a softwater BLM, together with 2 newly developed multiple linear regressions (MLRs)-a trophic level-specific MLR and a pooled MLR. Each of the 4 models was used to normalize a nickel ecotoxicity dataset (combined tropical and temperate data) to an index condition of pH 7.5, 6 mg Ca/L, 4 mg Mg/L, (i.e., approximately 30 mg CaCO3 /L hardness), and 0.5 mg DOC/L. The trophic level-specific MLR outperformed the other 3 models, with 79% of the predicted 10% effect concentration (EC10) values within a factor of 2 of the observed EC10 values. All 4 models gave similar normalized species sensitivity distributions and similar estimates of protective concentrations (PCs). Based on the index condition water chemistry proposed as the basis of the national guideline value, a protective concentration for 95% of species (PC95) of 3 µg Ni/L was derived. This guideline value can be adjusted up and down to account for site-specific water chemistries. Predictions of PC95 values for 20 different typical water chemistries for Australia and New Zealand varied by >40-fold, which confirmed that correction for nickel bioavailability is critical for the derivation of site-specific guideline values. Environ Toxicol Chem 2021;40:100-112. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Acute and Chronic Toxicity of Nickel and Zinc to a Laboratory Cultured Mayfly (Neocloeon triangulifer) in Aqueous but Fed Exposures.

Aquatic insects are poorly represented in water quality criteria, and previous studies have suggested a lack of sensitivity in acute toxicity tests despite observational studies demonstrating the contrary. Our objectives were to determine the toxicity of nickel (Ni) and zinc (Zn) to the mayfly Neocloeon triangulifer in fed acute (96-h) and chronic exposures to estimate aqueous effect concentrations while acknowledging the importance of dietary exposure for these insects. For the chronic tests, we conducted preliminary full-life cycle (~25-30 d) and subchronic (14 d) exposures to compare the relative sensitivity of the 2 test durations under similar conditions (i.e., feeding rates). Observing similar sensitivity, we settled on 14 d as the definitive test duration. Furthermore, we conducted experiments to determine how much food could be added to a given volume of water while minimally impacting dissolved metal recovery; a ratio of food dry mass to water volume (<0.005) achieved this. In the 14-d tests, we obtained a median lethal concentration and most sensitive chronic endpoint of 147 and 23 µg/L dissolved Ni (acute to chronic ratio [ACR] = 6.4), respectively, and 81 (mean value) and 10 µg/L dissolved Zn (ACR = 8.1), respectively. The acute values are orders of magnitude lower than previously published values for mayflies, probably most importantly due to the presence of dietary exposure but also potentially with some influence of organism age and test temperature. Environ Toxicol Chem 2020;39:1196-1206. © 2020 SETAC.

A microcosm study to support aquatic risk assessment of nickel: Community-level effects and comparison with bioavailability-normalized species sensitivity distributions.

The aquatic risk assessment for nickel (Ni) in the European Union is based on chronic species sensitivity distributions and the use of bioavailability models. To test whether a bioavailability-based safe threshold of Ni (the hazardous concentration for 5% of species [HC5]) is protective for aquatic communities, microcosms were exposed to 5 stable Ni treatments (6-96 µg/L) and a control for 4 mo to assess bioaccumulation and effects on phytoplankton, periphyton, zooplankton, and snails. Concentrations of Ni in the periphyton, macrophytes, and snails measured at the end of the exposure period increased in a dose-dependent manner but did not indicate biomagnification. Abundance of phytoplankton and snails decreased in 48 µg Ni/L and 96 µg Ni/L treatments, which may have indirectly affected the abundance of zooplankton and periphyton. Exposure up to 24 µg Ni/L had no adverse effects on algae and zooplankton, whereas the rate of population decline of the snails at 24 µg Ni/L was significantly higher than in the controls. Therefore, the study-specific overall no-observed-adverse-effect concentration (NOAEC) is 12 µg Ni/L. This NOAEC is approximately twice the HC5 derived from a chronic species sensitivity distribution considering the specific water chemistry of the microcosm by means of bioavailability models. Thus, the present study provides support to the protectiveness of the bioavailability-normalized HC5 for freshwater communities.

Assessment of the effects of nickel on benthic macroinvertebrates in the field.

A field-based evaluation of the biological effects of potential nickel (Ni) exposures was conducted using monitoring data for benthic macroinvertebrates and water chemistry parameters for streams in England and Wales. Observed benthic community metrics were compared to expected community metrics under reference conditions using RIVPACS III+ software. In order to evaluate relationships between Ni concentrations and benthic community metrics, bioavailable Ni concentrations were also calculated for each site. A limiting effect from Ni on the 90th percentile of the maximum achievable ecological quality was derived at "bioavailable Ni" exposures of 10.3 µg l(-1). As snails have been identified as particularly sensitive to nickel exposure, snail abundance in the field in response to nickel exposure, relative to reference conditions, was also analysed. A "low effects" threshold for snail abundance based on an average of spring and autumn data was derived as 3.9 µg l(-1) bioavailable Ni. There was no apparent effect of Ni exposure on the abundance of Ephemeroptera (mayflies), Plecoptera (stoneflies) or Tricoptera (caddisflies) when expressed relative to a reference condition within the range of "bioavailable Ni" exposures observed within the dataset. Nickel exposure concentrations co-vary with the concentrations of other stressors in the dataset, and high concentrations of Ni are also associated with elevated concentrations of other contaminants.

Recommendations to improve wildlife exposure estimation for development of soil screening and cleanup values.

An integral component in the development of media-specific values for the ecological risk assessment of chemicals is the derivation of safe levels of exposure for wildlife. Although the derivation and subsequent application of these values can be used for screening purposes, there is a need to identify the threshold for effects when making remedial decisions during site-specific assessments. Methods for evaluation of wildlife exposure are included in the US Environmental Protection Agency (USEPA) ecological soil screening levels (Eco-SSLs), registration, evaluation, authorization, and restriction of chemicals (REACH), and other risk-based soil assessment approaches. The goal of these approaches is to ensure that soil-associated contaminants do not pose a risk to wildlife that directly ingest soil, or to species that may be exposed to contaminants that persist in the food chain. These approaches incorporate broad assumptions in the exposure and effects assessments and in the risk characterization process. Consequently, thresholds for concluding risk are frequently very low with conclusions of risk possible when soil metal concentrations fall in the range of natural background. A workshop held in September, 2012 evaluated existing methods and explored recent science about factors to consider when establishing appropriate remedial goals for concentrations of metals in soils. A Foodweb Exposure Workgroup was organized to evaluate methods for quantifying exposure of wildlife to soil-associated metals through soil and food consumption and to provide recommendations for the development of ecological soil cleanup values (Eco-SCVs) that are both practical and scientifically defensible. The specific goals of this article are to review the current practices for quantifying exposure of wildlife to soil-associated contaminants via bioaccumulation and trophic transfer, to identify potential opportunities for refining and improving these exposure estimates, and finally, to make recommendations for application of these improved models to the development of site-specific remedial goals protective of wildlife. Although the focus is on metals contamination, many of the methods and tools discussed are also applicable to organic contaminants. The conclusion of this workgroup was that existing exposure estimation models are generally appropriate when fully expanded and that methods are generally available to develop more robust site-specific exposure estimates. Improved realism in site-specific wildlife Eco-SCVs could be achieved by obtaining more realistic estimates for diet composition, bioaccumulation, bioavailability and/or bioaccessibility, soil ingestion, spatial aspects of exposure, and target organ exposure. These components of wildlife exposure estimation should be developed on a site-, species-, and analyte-specific basis to the extent that the expense for their derivation is justified by the value they add to Eco-SCV development.

Field measurement of nickel sediment toxicity: role of acid volatile sulfide.

A field experiment was performed in four freshwater systems to assess the effects of Ni on the benthic macroinvertebrate communities. Sediments were collected from the sites (in Belgium, Germany, and Italy), spiked with Ni, and returned to the respective field sites. The colonization process of the benthic communities was monitored during a nine-month period. Nickel effect on the benthos was also assessed in the context of equilibrium partitioning model based on acid volatile sulfides (AVS) and simultaneously extracted metals (SEM). Benthic communities were not affected at (SEM - AVS) ≤ 0.4 µmol/g, (SEM - AVS)/fraction of organic carbon (f(OC)) < 21 µmol/g organic carbon (OC). Sediments with (SEM - AVS) > 2 µmol/g, (SEM - AVS)/f(OC) > 700 µmol/g OC resulted in clear adverse effects. Uncertainty about the presence and absence of Ni toxicity occurred at (SEM - AVS) and (SEM - AVS)/f(OC) between 0.4 to 2 µmol/g and 21 to 700 µmol/g OC, respectively. The results of our study also indicate that when applying the SEM:AVS concept for predicting metal toxicity in the field study, stressors other than sediment characteristics (e.g., sorption capacity), such as environmental disturbances, should be considered, and the results should be carefully interpreted.