Long-term effects of the antifouling booster biocide Irgarol 1051 on periphyton, plankton and ecosystem function in freshwater pond mesocosms.

Irgarol is a highly effective biocide used in antifouling coatings to prevent the growth of periphyton. Environmental concentrations of Irgarol in marine and freshwater have often exceeded the effect concentrations of autotrophic organisms tested in the laboratory and give reason for concern that natural periphyton communities may be endangered. A 150 days freshwater mesocosm study in 8 indoor ponds was conducted at nominal concentrations between 0.04 and 5 microgL(-1) in order to investigate the effects of Irgarol on periphyton and plankton. The results demonstrated that periphyton communities were strongly affected after single applications of 1 and 5 microgL(-1) Irgarol. For these concentrations no recovery was observed in the course of the study. For chlorophytes, the EC(50) (nominal, 135 days) was 0.34 microgL(-1). Phytoplankton also decreased in abundance directly after Irgarol application but recovered after a few weeks, as Irgarol concentrations rapidly decreased in the water body and nutrient levels increased due to lack of competition with periphyton and macrophytes. Zooplankton was indirectly affected by Irgarol. Principle response curve analysis revealed a species shift from macrophyte associated zooplankton species to free-swimming species. For species of cyclopoid copepods and ostracods the EC(50) was, respectively, 0.09 and 0.11 microgL(-1). The study simulated a best-case scenario since the mesocosms were dosed only once. Under field conditions, however, permanent exposure of organisms to Irgarol is more likely due to permanent leaching from painted ship hulls. Therefore, the effects presented in this study most likely underestimate the effects under natural conditions.

The effects of a cyanobacterial crude extract on different aquatic organisms: evidence for cyanobacterial toxin modulating factors.

In an aquatic ecosystem, during cyanobacterial bloom lysis, a mixture of toxins and other cyanobacterial and bacterial components will be present in the water, acting on aquatic organisms. Most of the research into toxic effects of cyanobacteria has involved the use of purified toxins. In this study, the "real-life" situation of a cyanobacterial lysis event was investigated. For this purpose, intact cells from a natural cyanobacterial bloom from Lake Müggelsee, Berlin, were taken and the cells were broken by repeated freeze/thaw cycles. This crude extract was used to expose several aquatic organisms ranging from microalgae (Scenedesmus armatus), macrophyte (Ceratophyllum demersum), invertebrate (Chaoborus crystallinus) up to fish eggs (Danio rerio) to look at several physiological parameters such as detoxication enzyme activity and, in the case of the microalgae and the macrophyte, also the effect on activity of photosynthesis. In all the tests, the cyanobacterial crude extract caused stronger effects than the pure cyanobacterial toxins used in equivalent concentrations.