En inventering av bottenfauna i Trönningeån med två biflöden

Sammanfattning: Benthic macroinvertebrates are usually small animals living in our lentic and lotic ecosystems, they have been used as indicators of water quality and biodiversity for a long time. Dam removals have become one of the “go-to” conservation methods for restoring connectivity in lotic ecosystems and thereby enabling passage upstream for migrating species. In Sweden, a large part of rivers and streams have dams present which act as migration barriers. Hushållningssällskapet Halland runs a project, LIFE-Goodstream in which a dam considered a migration barrier was removed in the stream Trönningeån. This report has three focus areas 1) the ecological effects of the dam removal while 2) considering the effect on the species composition of the orders Ephemeroptera (Mayflies), Plecoptera (Stoneflies), Trichoptera (Caddisflies) and Odonata (Dragonflies) in the stream Trönningeån with two tributaries and finally 3) suggest appropriate conservation methods for the future. By examining the benthic macroinvertebrate community our study showed that a small dam removal can have a clear positive effect on water quality, changing the water status classification from low water quality to high. Although there was no effect on the species diversity by the dam removal, a turnover in species composition became obvious after the examination. Moreover, we learned that Trichoptera was the most present order in two out of the three streams while Odonata was the least represented order. Also, bottom substrate, velocity and riparian zone have larger impact on species composition than adjacent environments. Re-meandering streams to further increase biodiversity while also ensuring water quality, is an essential method for a thriving conservation work in the future.