Significance of subfossile chironomid remains in classification of shallow lakes

The relative species composition of subfossile chironomid headcapsules in surface sediments from ten shallow Danish lakes of different trophic status were analysed through similarity indices and multidimensional scaling. It was possible to distinguish between high and low productivity lakes by means of subfossile remains. The low productivity shallow lakes (TP<150 mu g P1(-1)) were characterised by the taxa Psectrocladius, Pseudochironomus, Microtendipes and Pentaneurini. The high productivity lakes (TP>150 mu g P1-1) show similarities to littoral communities in eutrophic stratified lakes and are represented by genera such as Cricotopus, Procladius, Microchironomus and Chironomus. In surface samples from Lake Stigsholm subfossile species composition was compared with species composition in samples of trapped adult midges and samples of living larvae. The relative species composition between the three sample types varied considerably. Samples of living larvae showed a high degree of variation within the lake while surface sediment samples of subfossile chironomid remains seemed to be a persistent and reliable tool in classification of shallow lakes.