Predicting and observing responses of algal communities to photosystem ii‐herbicide exposure using pollution‐induced community tolerance and species‐sensitivity distributions

Abstract

Various test strategies are in use in ecotoxicology to assess the potential risks of toxicants on aquatic communities. The species-sensitivity distribution concept (SSD) works by arranging single-species laboratory test data in a cumulative frequency distribution. The pollution-induced community tolerance concept (PICT) uses observable community responses by measuring increases in community tolerance caused by the replacement of sensitive species after exposure. The aim of this study was to compare these two concepts in assessing the effects of three herbicides. Atrazine, prometryn, and isoproturon were found to increase community tolerance by a factor up to six. Atrazine increased community tolerance only at higher test concentrations (0.125 mg L(-1)). Species-sensitivity distributions correspond well to community responses: The median effective concentrations (EC50s) of untreated periphyton communities tested covered 55 to 65% of affected species represented in the SSD. The sensitivities of tolerant algal communities shifted to the right end of the SSDs. In the microcosm experiments, higher test concentrations affected biomass, species numbers, and community structure. Community tolerance could not be induced any further, suggesting that these concentrations represent a maximum of functional redundancy of a functional group. At higher concentrations, even the least-sensitive species are affected. These results can be interpreted as a confirmation of the SSD concept by observed algal community responses, when applied to photosystem II (PSII)-inhibiting herbicides.

Influence of slight differences in environmental conditions (light, hydrodynamics) on the structure and function of periphyton

“…The general characteristics of periphyton are known to change as it matures (Lock 1993;Costerton et al 1995;Schmitt-Jansen and Altenburger 2005). In our experiments, the biomass, number of algal and bacterial cells, and primary production increased under all experimental conditions.…”

Herbicide Contamination of Freshwater Ecosystems: Impact on Microbial Communities

“…After exposure to these pollutants for long enough, sensitive species or strains will be eliminated and tolerant ones will be selected, and the resulting restructured community will become more tolerant. Increased tolerance in a community can therefore be regarded as indicative of a direct impact of a pollutant on this community (for example for microalgal communities, see Bérard et al, 2003;Schmitt-Jansen & Altenburger, 2005). This pollution-induced community tolerance can be estimated by means of various different metabolic tests.…”

An in situ toxicity assay with the local phytoplankton community

“…Although the compositional pattern of a phytoplankton community dominated by green algae was observed at both the reference and the impacted sites, shifts in the taxonomic composition of the communities were identified as a result of the different sensitivities of the four major taxonomic groups to the metal contamination. Such alterations in the productivity and structure of algal communities can be propagated in adverse effects on the structure and function of aquatic communities, through indirect cascading effects on higher trophic levels (e.g., by disrupting the function of primary producers, changing the food edibility, or altering physicochemical conditions) [8,51,52].…”