Peat mining increasing fine-grained organic matter on the riffle beds of boreal streams

Effects of particulate matter (PM) loading on riffle bed quality were studi ed in small boreal streams in northern Finland. Feat mining increased the a mount of particulate organic matter (POM) on riffle beds. POM consisted mai nly of small particles, of diameter less than 1 mm. The finest PM particles , of diameter less than 0.075 mm, were shown to carry Fe, and there was a p ositive relationship between PM loading and the amount of Fe on the riffle beds. The results indicate that loading with fine-grained POM and the incre ase in the amount of Fe attached to finest PM particles may be a cause of t he changes observed in benthic invertebrate and fish communities in riffles affected by peat mining.