The sensitivity of diatom taxonomy and trait-based endpoints to chemicals has been poorly used so far in Environmental Risk Assessment. In this study, diatom assemblages in outdoor flow-through mesocosms were exposed to thiram (35 and 170 mu g/L), and a hydrocarbon emulsion (HE; 0.01, 0.4, 2 and 20 mg/L). The effects of exposure were assessed for 12 weeks, including 9 weeks post-treatment, using taxonomic structure and diversity, bioindication indices, biological traits, functional diversity indices, indicator classes and ecological guilds. For both chemicals, diversity increased after the treatment period, and responses of ecological traits were roughly identical with an abundance increase of motile taxa tolerant to organic pollution and decrease of low profile taxa. Bioindication indices were not affected. Traits provided a complementary approach to biomass measurements and taxonomic descriptors, leading to a more comprehensive overview of ecological changes due to organic chemicals, including short- and long-term effects on biofilm structure and functioning. (C) 2014 Elsevier Ltd. All rights reserved.

Antibiotics are a contaminant class of worldwide concern as they are frequently detected in aquatic ecosystems. To better understand the impacts of antibiotics on aquatic ecosystems, we conducted an outdoor mesocosm experiment in which aquatic communities were exposed to different concentrations of the antibiotic sulfamethoxazole (0, 0.15, 1.5, 15 and 150 μg/L). These concentrations include mean (0.15 μg/L) and maximum detected concentrations (15 and 150 μg/L) in aquatic ecosystems worldwide. Sulfamethoxazole was applied once a week for eight consecutive weeks to 1530 L outdoor mesocosms in the Netherlands, followed by an eight-week recovery period. We evaluated phytoplankton-, bacterial- and invertebrate responses during and after sulfamethoxazole exposure and assessed impacts on organic matter decomposition. Contrary to our expectations, consistent treatment-related effects on algal and bacterial communities could not be demonstrated. In addition, sulfamethoxazole did not significantly affect zooplankton and macroinvertebrate communities. However, some effects on specific taxa were observed, with an increase in Mesostoma flatworm abundance (NOEC of <0.15 μg/L). In addition, eDNA analyses indicated negative impacts on the insects Odonata at a sulfamethoxazole concentration of 15 μg/L. Overall, environmentally relevant sulfamethoxazole concentration did not result in direct or indirect impairment of entire aquatic communities and ecological processes in our mesocosms. However, several specific macroinvertebrate taxa demonstrated significant (in)direct effects from sulfamethoxazole. Comparison of the results with the literature showed inconsistent results between studies using comparable, environmentally relevant, concentrations. Therefore, our study highlights the importance of testing the ecological impacts of pharmaceuticals (such as sulfamethoxazole) across multiple trophic levels spanning multiple aquatic communities, to fully understand its potential ecological threats.

Antibiotics are a contaminant class of worldwide concern as they are frequently detected in aquatic ecosystems. To better understand the impacts of antibiotics on aquatic ecosystems, we conducted an outdoor mesocosm experiment in which aquatic communities were exposed to different concentrations of the antibiotic sulfamethoxazole (0, 0.15, 1.5, 15 and 150 μg/L). These concentrations include mean (0.15 μg/L) and maximum detected concentrations (15 and 150 μg/L) in aquatic ecosystems worldwide. Sulfamethoxazole was applied once a week for eight consecutive weeks to 1530 L outdoor mesocosms in the Netherlands, followed by an eight-week recovery period. We evaluated phytoplankton-, bacterial- and invertebrate responses during and after sulfamethoxazole exposure and assessed impacts on organic matter decomposition. Contrary to our expectations, consistent treatment-related effects on algal and bacterial communities could not be demonstrated. In addition, sulfamethoxazole did not significantly affect zooplankton and macroinvertebrate communities. However, some effects on specific taxa were observed, with an increase in Mesostoma flatworm abundance (NOEC of <0.15 μg/L). In addition, eDNA analyses indicated negative impacts on the insects Odonata at a sulfamethoxazole concentration of 15 μg/L. Overall, environmentally relevant sulfamethoxazole concentration did not result in direct or indirect impairment of entire aquatic communities and ecological processes in our mesocosms. However, several specific macroinvertebrate taxa demonstrated significant (in)direct effects from sulfamethoxazole. Comparison of the results with the literature showed inconsistent results between studies using comparable, environmentally relevant, concentrations. Therefore, our study highlights the importance of testing the ecological impacts of pharmaceuticals (such as sulfamethoxazole) across multiple trophic levels spanning multiple aquatic communities, to fully understand its potential ecological threats.

Biological stress responses in individuals are used as indicators of pollution in aquatic ecosystems, but detecting ecologically relevant responses in whole communities remains a challenge. We developed an experimental approach to detect the effects of pollution on estuarine communities using field-based mesocosms. Mesocosms containing defaunated sediments from four estuaries in southeastern Australia that varied in sediment contamination were transplanted and buried in sediments of the same four estuaries for six weeks. Mesocosm sediment properties and metal concentrations remained representative of their source locations. In each estuary, fauna communities associated with sediments derived from the site with the highest metal concentrations were significantly different from other communities. This pattern was evident for some of the individual taxa, in particular the polychaete Capitella sp. Consistent responses across estuaries suggest numbers of individuals, and especially Capitella sp., could be used to identify contaminated sediments in estuaries with similar fauna and site characteristics.