Depth-distribution of surface sediment diatoms in Lake Tovel, Italy

摘要

Surface sediment, which covers large parts of lake bottoms, is a widespread microhabitat for which specific algae quantification procedures have been developed (Eaton & Moss 1966). Sediment habitat can promote selection of diatom taxa with specific characteristics such as motility, which is required to avoid being buried and losing access to light (Wetzel 2001). Diatoms inhabiting the surface sediment of lakes have also been shown to perform vertical migrations in the upper portion of the sediment; cell numbers on the surface start to increase before sunrise and reach a maximum at about midmorning (Wetzel 2001). Notwithstanding these peculiarities, the ecology of depth distribution of surface sediment diatoms in lakes is a topic which has received limited attention (Round 1956, Round 1961, Bradbury & Winter 1976, Stevenson & Stoermer 1981, Gaiser & Johansen 2000). An aspect explored to some extent is the analysis of the depth distribution of taphocoenoses, a field of study needed to develop training sets to reconstruct lake-level fluctuations (Lotter 1988, Yang & Duthie 1995) often linked to climate change in the Holocene (Bigler 2001). However, ecological aspects, particularly the identification of the most influential factors by means of mul-tivariate analysis, have been only seldom considered (Wolin & Duthie 1999).