Restoration effects on benthic macroinvertebrate diversity and community composition in a river

Sammanfattning: Physical restoration efforts are common methods to restore running waters containingdegraded ecosystems due to anthropogenic activities such as irrigation, ditching, dammingand flood prevention. The goal is usually to restore waters to a more natural state, creatingmore physically complex habitats supporting a larger number of species of both fish andinvertebrates, hence increasing biodiversity. This master thesis is investigating if there havebeen positive effects on invertebrate species composition and biodiversity of restoredcompared to unrestored reaches of Hargsån, a small river located on the coast of Uppland,Sweden.Collection of benthic macroinvertebrates was done by sampling different microhabitats(bottom, dead wood and stones) in 3 different localities, a restored reach (the bypass), anunrestored reach (the bridge) and an unrestored reach with a migratory blockage (furthestupstream). Invertebrates were identified to the lowest taxonomic level and length-measured,and metrics such as Simpson and Shannon biodiversity and richness was calculated with thisdata to see if there were any differences with respect to benthic invertebrate communitycomposition and biodiversity between the localities or habitats.The results of the study show that there has been a shift in community composition of benthicinvertebrate fauna in the restored reach of Hargsån, but it is still not clear if the Simpson andShannon biodiversity has increased. This might be due to the current succession state of thelocal ecosystem, considering that there has only been about 1,5 years since the restorationefforts were completed, but more studies of the river are needed to secure the causes of therestoration and its long-term effects.