The species sensitivity distribution approach compared to a microcosm study: a case study with the fungicide fluazinam.

We assessed the sensitivity of freshwater organisms (invertebrates and algae) to the fungicide Shirlan (active ingredient fluazinam) in single-species laboratory tests and in microcosms. Species sensitivity distribution (SSD) curves were constructed by means of acute toxicity data for 14 invertebrate species, since algae were much less sensitive. The EC(10)-based SSD gave a median HC(5) value of 0.6microgL(-1) and a 90% confidence interval of 0.1-1.9 microgL(-1). The EC(50)-based SSD gave a median HC(5) value of 3.9 microgL(-1) (90% confidence interval: 0.9-9.9 microgL(-1)). The microcosms were treated four times with Shirlan (concentration range: 0.4-250 microgL(-1)). Responses of the microcosm communities were followed. The 2 microgL(-1) treatment was the no-observed-effect concentration (NOEC(microcosm)). The 10 microgL(-1) treatment resulted in short-term effects on a few zooplankton taxa. Clear effects were observed at 50 and 250 microgL(-1). The responses in the microcosms were in line with the toxicity data for the tested lab species. The median EC(10)-based HC(5) and the lower limit EC(50)-based HC(5) were lower, and the median EC(50)-based HC(5) was slightly higher than the NOEC(microcosm). This is consistent with other studies that compared SSDs with responses in model ecosystems that received repeated applications of pesticides.

Ecological effects of spring and late summer applications of lambda-cyhalothrin on freshwater microcosms.

The aim of the study was to compare the effects of the pyrethroid insecticide lambda-cyhalothrin (treated at 10, 25, 50, 100, 250 ng active ingredient a.i./L) on a drainage ditch ecosystem in spring and late summer. Microcosms (water volume approximately 430 L) were established using enclosures in a 50-cm-deep experimental ditch system containing communities typical of macrophyte-dominated freshwater ecosystems. Effects on macroinvertebrates, zooplankton, phytoplankton, macrophytes, and community metabolism were assessed and evaluated using univariate and multivariate statistical techniques. The macroinvertebrate community responded most clearly to treatment and, as anticipated, insects and crustaceans were among the most sensitive organisms. Statistical analysis showed that the underlying community structure was significantly different between the spring and summer experiments. However, the most sensitive species (Chaoborus obscuripes and Gammarus pulex) were abundant in spring as well as in late summer. In spring and late summer, only slight and transient effects were observed at the community level in the 10-ng/L treatment. Overall, the study did not show substantial differences in the responses of sensitive taxa between spring and late summer treatments, and effects thresholds were similar irrespective of season of treatment.