Effects of Stream Channelization on Aquatic Macroinvertebrates, Buena Vista Marsh, Portage County, Wisconsin

Abstract

Project objectives were to determine the effects of stream channelization on biomass and composition of stream benthos and drift and on water quality and temperature. Drift and substrate-stratified, quantitative benthos samples were collected and stream discharge measured in upstream and downstream new ditch, old ditch, and natural stream sites, at approximately 6-week intervals during the ice-free period of the year. Water chemistry samples were collected at approximately 6-week intervals throughout the year and temperatures recorded continuously with thermographs. Benthic biomass and density were lowest in sand and higher in aquatic vegetation, silt-detritus, and gravel (productive substrates) , which provided stable surfaces for reattachment of drifting invertebrates and interstices for entrapment of drifting seston. Benthic biomass and density were positively correlated, whereas drifting invertebrate biomass and density, and density of drifting seston, were negatively correlated with percent composition of the productive substrates. Percent composition of the productive substrates was highest in the natural stream, followed by the old and new ditch in the upstream area, and highest in the new ditch, followed by the old ditch and natural stream in the downstream area. Water quality and temperature, similar among sites, probably were moderated by groundwater inflow.