Division of Soil and Water Management, KU Leuven, Heverlee, Belgium.
Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent University, Ghent, Belgium.
Environ Toxicol Chem. 2024 Nov;43(11):2350-2364. doi: 10.1002/etc.5970. Epub 2024 Aug 27.
Effect assessments of metals are mostly based on single-metal, single-species tests, thereby ignoring metal-mixture effects and indirect effects through species interactions. We tested the combined effects of metal and species interactions in two-trophic algal-daphnid microcosms. Metal-mixture effects on daphnid communities may propagate from effects on the generally more sensitive algal communities. Four different algal communities (three species each), with and without addition of the same daphnid community (three species) were exposed to single metals and one metal mixture (17:17:51 µg/L Ni:Cu:Zn). Daphnid densities were negatively affected by metals in the two-trophic test, the magnitude of which depended on the algal community composition. Algal densities were overall positively affected by the metals in the two-trophic test but negatively in the single-trophic test, illustrating an indirect positive effect in the two-trophic system due to a reduced grazing pressure. Metal effects on daphnid communities in the two-trophic test (day 21) were correlated with metal effects on the single-trophic-level algal communities during exponential growth (R = 0.55, p = 0.0011). This finding suggests that metal effects propagate across trophic levels due to a reduced food quantity. However, the indirect positive effects on algal densities, resulting in abundant food quantity, suggests that metal effects can also propagate to daphnids due to a reduced food quality (not measured directly). Metal-mixture interactions on daphnid densities varied during exposure, but were additive or antagonistic relative to independent action when final daphnid densities were considered (day 56). This suggests stronger indirect effects of the mixture compared with the single metals. Overall, our study highlights the dynamic aspect of community-level effects, which empirical reference models such as independent action or concentration addition cannot predict. Environ Toxicol Chem 2024;43:2350-2364. © 2024 SETAC.
金属的效应评估主要基于单金属、单物种测试，从而忽略了金属混合物的效应和通过物种相互作用的间接效应。我们在两种营养层次的藻类-水蚤微宇宙中测试了金属和物种相互作用的综合效应。金属混合物对水蚤群落的影响可能会通过对通常更敏感的藻类群落的影响而传播。四个不同的藻类群落（每个有三个物种），有和没有添加相同的水蚤群落（三个物种），分别暴露于单一金属和一种金属混合物（17:17:51μg/L 的 Ni:Cu:Zn）。在双营养层次测试中，金属对水蚤的密度有负面影响，其大小取决于藻类群落的组成。在双营养层次测试中，藻类的密度总体上受到金属的正影响，但在单营养层次测试中则受到负影响，这表明由于放牧压力降低，在双营养系统中存在间接的正效应。在双营养层次测试中（第 21 天），金属对水蚤群落的影响与金属对单营养层次藻类群落在指数增长期间的影响相关（R=0.55，p=0.0011）。这一发现表明，由于食物数量的减少，金属效应会在营养层次上传播。然而，由于食物质量的降低，藻类密度的间接正效应导致了丰富的食物数量，这表明金属效应也可以通过减少食物质量（未直接测量）传播到水蚤身上。在暴露期间，金属混合物对水蚤密度的相互作用会发生变化，但当考虑最终水蚤密度时，相对于独立作用，是相加或拮抗的（第 56 天）。这表明混合物的间接效应比单一金属更强。总体而言，我们的研究强调了群落水平效应的动态方面，而经验参考模型（如独立作用或浓度相加）无法预测这一方面。环境毒理化学 2024；43：2350-2364。©2024 SETAC。
