An Assessment of In-stream Sampling Activity of Macroinvertebrates and Stream Channelization in Dug Run, Allen County, Ohio, USA

Macroinvertebrates are good indicators of stream quality. Changes in populations of sensitive macroinvertebrates help to show stressors to the stream. Student sampling of a section of Dug Run in northwestern Ohio has occurred since 2015. This work has been to identify how changes on the campus including construction, tree removal, and channelization may be impacting stream macroinvertebrates. Student sampling, however, also causes disturbances that may negatively impact macroinvertebrate populations. A break in student sampling—due first to the use of an adjacent off-site location in 2019 and then to COVID-19 beginning in 2020—was expected to impact the number of mayfly nymphs and caddisfly larvae captured, both considered sensitive macroinvertebrates in the stream. To measure the impact of channelization in Dug Run, the study area was split into a channelized reach, an upstream reach, and a downstream reach. Stream habitat was also studied in each reach with macroinvertebrates collected from riffles, undercuts, and pools. After a break in sampling, caddisfly larvae increased initially but have declined in the 2 following years, while mayfly nymphs increased in the last 2 years of the study. No significant differences were found in stream quality monitoring (SQM) index scores between the channelized reach compared to upstream and downstream reaches (H = 4.15; p = 0.126). There was a significant difference in taxa richness among pools, riffles, and undercuts (H = 14.09; p < 0.001). A significant difference was also found in the moderately sensitive macroinvertebrates captured in riffles between the channelized, upstream, and downstream reaches (H = 6.82; p = 0.033). A break in sampling resulted in an initial increase in mayfly nymph and caddisfly larvae samples, but it appears a variety of factors may be responsible for the numbers captured. The channelized reach had higher numbers of scuds and crayfish in riffles among the 3 reaches, which may be the result of a change in their distribution related to lack of undercuts. Both scuds and crayfishwere found in significantly greater abundance in undercuts compared to pools and riffles.