Species diversity in postglacial diatom lake communities of Finland

Abstract

Species diversity in three sections of Flandrian sediment from the Finnish Lake District was studied, together with orthodox diatom stratigraphy, to analyse the pattern of change in diatom communities over the postglacial time. The general agreement of the two approaches is clear, and in particular there is a positive direct relationship between the temporal development of these aquatic systems and changes in the diatom diversity. As indicated by both the quantitative inventory and the species diversity, these diatom communities consisted of few species immediately after glaciation at 10 000 radiocarbon years B.P. The minimum diversity at 9 000 B.P. coincides with the maximum of Melosira islandica ssp. helvetica. A trend to development of a larger number of equally abundant species, and higher total diversity followed isolation of the lake from the Baltic Sea at 8 000 B.P. This is consistent with earlier results of Duthie and Sreenivasa that the number of individuals and total diversity of the samples increase over the postglacial time.