A pulse of endosulfan-contaminated sediment affects macroinvertebrates in artificial streams

The toxicity of the organochlorine pesticide endosulfan to macroinvertebrate communities was tested using a system of 24 artificial streams. Macroinvertebrate communities in the streams were exposed to a range of endosulfan concentrations for a 12-h period and then monitored for 96 h. Endosulfan was prebound to fine river sediment and applied to the streams as a contaminated sediment slurry. This did not cause changes in the structure of benthic communities; however, significant changes (P<0.05) in the abundance of several macroinvertebrate taxa in drift were detected in the streams receiving the highest (6.14 microg/L) dose. Increased drift may have implications for recolonization processes in lowland rivers, and, as such, pulses of contaminated sediment are likely to result in significant effects on macroinvertebrate populations and communities. This study highlights the utility of artificial stream systems for detecting sublethal effects and the need for population and community-level endpoints to be included in such studies.