Testing the benthic lake type concept based on chironomid associations in some Finnish lakes using multivariate statistical methods

The profundal chironomid associations in 9 Finnish lakes were analyzed using a hierarchial cluster analysis technique in order to test the usefulness of the lake typology of Brundin in the study area. The classification results were evaluated by analyzing the corresponding physico-chemical water quality data with discriminant analysis. The same procedure was also applied with the shallow water associations. The results showed that the lake typology of Brundin is a valid basis for monitoring stratified lakes. They supported the thesis holding that the availability of food is the primary controlling mechanism in the profundal chironomid communities. In the shallow water region the difficulties in creating benthic lake typologies are apparent. The best classification results in relation to the water quality and trophic status were achieved at a depth of 3—5 m. It is necessary to divide the littoral and sublittoral into subzones and to compare lakes separately in them. The results showed that it is possible to find characteristic benthic types in shallow lakes as well, these being typical to Finland. Further supporting taxonomic research on quantitatively important lake chironomids is required before a useful lake typology can be established for the shallow water region.