Patterns of initial benthic recolonization of a reclaimed coal strip-mined river channel

Abstract

Benthic macroinvertebrate samples were taken at sampling stations upstream of, downstream of, and within a newly opened channel of the Tongue River in Wyoming. The channel, reclaimed from coal strip-mining, contained layers of topsoil, gravel, and small to medium cobble. Benthic recolonization progressed towards maximum densities following terms of a power function. The mayflies of the genus Baetis were the primary colonizers. Colonization occurred primarily by drift of aquatic insects and algal mats in the first 14 days of channel opening. Some upstream migration, particularly by the dragonfly Ophiogomphus, was observed. Attainment of maximum diversity lagged density by 20 to 30 days. This period represented a time of dynamic adjustment within the community to match the undisturbed source area communities. The combined effects of differential drift rates and distances for aquatic insects and detrital material were responsible for the rather predictable patterns of colonization as well as the sequentially decreasing diversity values as distance from the upstream source areas increased.