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

Abstract

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 mg/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 mg Ni/L and 96 mg Ni/L treatments, which may have indirectly affected the abundance of zooplankton and periphyton. Exposure up to 24 mg Ni/L had no adverse effects on algae and zooplankton, whereas the rate of population decline of the snails at 24 mg Ni/L was significantly higher than in the controls. Therefore, the study-specific overall no-observed-adverse-effect concentration (NOAEC) is 12 mg 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.

The Effects of Nickel on the Structure and Functioning of a Freshwater Plankton Community Under High Dissolved Organic Carbon Conditions: A Microcosm Experiment

“…Overall, based on the present study, the procedure to derive the HC5 as currently implemented in European legislative frameworks (which includes bioavailability normalizations of toxicity data to the physicochemistry of the receiving waters) protects against clear effects on plankton community structure and function at high DOC. This conclusion is in agreement with that of Hommen et al () for a plankton‐dominated community at lower DOC concentrations. Our study also showed that some individual plankton species are affected at the HC5, but this is not in conflict with the definition of the HC5, at which 95% (and not 100%) of the species are predicted to be unaffected.…”

“…In addition, exposures to Ni concentrations that were up to 4 times higher than the bioavailability‐normalized HC5 did not affect the phytoplankton or the zooplankton community (Hommen et al ). The test system of Hommen et al () represented a rather high Ni bioavailability situation (high pH and low‐to‐medium DOC: median pH of 8.6 and median DOC concentration of 3.9 mg/L), in which the median bioavailability‐normalized HC5 of 5.5 µg dissolved Ni/L was relatively close to the baseline conditions used to derive the bioavailable EQS implemented under the WFD (4 µg dissolved Ni/L; European Commission ). Given the wide range of physicochemistry parameters in European waters, it is important to evaluate whether the bioavailability normalization procedure for Ni and its associated environmental threshold (HC5) that were developed with single‐species bioavailability models (Nys et al ) are also protective for complex communities under different bioavailability conditions.…”

The effects of a mixture of copper, nickel, and zinc on the structure and function of a freshwater planktonic community

“…1 because the relative abundance of this species comprises a large fraction of the total Cyanobacteria abundance (Figure A). These negative effects could have caused a positive effect on the abundance of the Chrysophyta, diatoms, and Cryptophyta in these metal mixture treatments (relative to the control) likely via competitive release, that is, reduced competition for nutrients with cyanobacteria . Despite the fact that diatoms are often considered very sensitive to metals, this was not reflected in our community, where cyanobacteria were clearly the most sensitive phytoplankton group under mixed Zn–Ni exposure.…”

“…This technique is used to analyze the statistical power of mesocosm and microcosm experiments and to determine effects at the community and population levels and is accepted by the European Food Safety Authority . More recently, the technique has also been used in the evaluation of microcosm studies with Ni and Zn . Based on the minimum detectable difference, the reliability of taxa for analysis can be determined, and as such, 3 categories of taxa can be distinguished.…”

Assessing the relevance of ecotoxicological studies for regulatory decision making

“…Hence, in order to increase the relevance of micro‐ and mesocosm tests to ERA, careful consideration of results from lower‐tier tests should be made when selecting species and populations to include in higher‐tier testing. For example, intentionally included populations of sensitive species of gastropods, as informed by laboratory ecotoxicological studies, were crucial for the interpretation of the relevance of a microcosm test for refining the environmental quality standard of Ni (Hommen et al ).…”