The Chironomid (Diptera) Subfossil Record of Lille Hovvatn (Norway), with a Comparison with a Similar Study in Adjacent Store Hovvatn

The subfossil chironomid community of Lille Hovvatn during the last 150 years was analysed. A short sediment core was taken in 1999, sliced at 0.5 cm intervals and dated using the 210Pb method. A total of 1588 specimens were identified, most of them to species level, and 37 chironomid taxa were found. Effects of acidification were recorded on several species up-core, especially in the distribution of Micropsectra insignilobus and Stictochironomus rosenshoeldi. Ordination analysis showed that the chironomid community of Lille Hovvatn is different from the one in Store Hovvatn based on the abundance of the various species, but that the species composition is almost identical in the two lakes. The reappearance of S. rosenshoeldi in the upper 1 cm of the sediment in Lille Hovvatn probably is the first response among the chironomids to the increased pH values measured in the lake during the last decade.