Benthic macroinvertebrate communities were studied after a small dam removal in a Korean stream. Study stream (Gokneung stream) is located at 30 km north of Seoul in a suburban rural area. Study dam (height 1.5 m, length 80 m) was removed in April 2006. Quantitative sampling (Surber net 30 x 30 cm, mesh 0.25 mm, 4 duplicates per habitat) was conducted from upstream (pool), dam-site, and downstream (riffle) habitats as well as from a control habitat beyond impoundment (ca. 300 m upstream from dam). Field surveys were conducted in March (before), June (after), September (after flood), and December in 2006. Environmental conditions, including substrate, were also monitored during the field surveys.
As a result, benthic macroinvertebrate communities have changed more diversely and abundantly after dam removal as the microhabitats, such as substrate, have changed in particular at the upstream habitat: species number (before 13 / after 14-21 spp.), McNaughton’s species dominance index (0.77 / 0.53-0.80), Shannon-Wiener’s species diversity index (2.04 / 2.00-2.95), and GPI (group pollution index) (1.92 / 1.89-2.00). Clingers and collector-filterers, such as hydropsychid caddisflies (Hydropsyche kozantschikovi), were considerably increased after dam removal. Flood enhanced the changes of benthic macroinvertebrate communities as well as those of microhabitats.