Benthic Macroinvertebrates In Streams Contaminated By Acid Mine Drainage – A Pilot Study From Thailand

Benthic macroinvertebrates were sampled by a D-Frame Dip net (450 µm mesh size) from 3 sites of a stream contaminated with acid mine drainage from a gold mine in Loei Province, Thailand. Sialis larvae (Insecta: Megaloptera: Sialidae) were dominant taxa (49%) in the high Arsenic upstream site 1 followed by dipteran larvae (26%), gastropods (15%) and Coleoptera (10%). The less contaminated, downstream site 3 was dominated by Coleoptera (32%), Ephemeroptera nymphs (24%) and Caridina (F. Atyidae, O. Decapoda-20%). Seventeen percent of mouthpart deformity of chironomid larvae was also found in site 2. It is preliminary concluded that the extent of contamination with mining waste water has affected both, taxon composition and the proportion of chironomids with deformed mouth parts.