The Combined and Interactive Effects of Zinc, Temperature and Phosphorus on the Structure and Functioning of a Freshwater Community

Environmental risk assessment of chemicals is mostly based on ecotoxicity studies under standard and not always realistic conditions of temperature and nutrient levels. In this collaborative study with universities of Wageningen, Leuven, and Namur, we performed an aquatic model ecosystem experiment, which showed that temperature and phosphorus loading to freshwater systems can modify the effects of chemical pollution on the structure (e.g. species composition) and functioning of aquatic ecosystems. We argue that factors like temperature and nutrient levels should be taken into account when evaluating the risks of chemicals in the environment.

 

Scientific abstract

Ecotoxicological studies mainly consist of single‐species experiments evaluating the effects of a single stressor. However, under natural conditions aquatic communities are exposed to a mixture of stressors. This study was set up to identify how the toxicity of zinc (Zn) is affected by increased temperature (T) and increased phosphorus supply (P) and how these interactions vary among species, functional groups, community structure and function. Aquatic microcosms were subjected to three Zn concentrations (background: no Zn added; 75 µg Zn/L and 300 µg Zn/L), two temperatures (16‐19 °C and 21‐24 °C) and 2 different P additions (low: 0.02 mg P L−1 week−1 and high: 0.4 mg P L−1week−1) for five weeks using a full factorial design. During this study consistent interactions between Zn and T were only rarely found at the species level (4%), but were frequently found at the functional group level (36%), for community structure (100%) and for community function (100%, such as Dissolved Organic Carbon concentrations and total chlorophyll). The majority of the Zn × T interactions were observed at 300 µg Zn/L and generally indicated a smaller effect of Zn at higher T. Furthermore, no clear indication was found that high P addition by itself significantly affected the overall effects of Zn on the community at any level of organisation. Interestingly though, 90% of all the Zn × T interactions observed at the species, group and community composition level were found under high P addition. Collectively, our study with the model chemical Zn suggests that temperature and phosphorus loading to freshwater systems should be accounted for in risk assessment, as these factors may modify the effects of chemicals on the structure and functioning of aquatic communities, especially at higher levels of biological organisation.

 

Full reference (link):

Van de Perre, D. , Roessink, I. , Janssen, C. R., Smolders, E. , De Laender, F. , Van den Brink, P. J. and De Schamphelaere, K. A. (2018), The Combined and Interactive Effects of Zinc, Temperature and Phosphorus on the Structure and Functioning of a Freshwater Community. Environ Toxicol Chem. Accepted Author Manuscript. . doi:10.1002/etc.4201

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