Accumulation of phytoplankton in lake sediments estimated from photosynthetic pigments.

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Phytoplankton pigments in sediment of Lake Kasumigaura were analyzed by HPLC.The depth profiles of echinenone and myxoxanthophyll, which are characteristic carotenoids of blue-green algae, showed an increase after the lock gate (Hitachigawa-suimon) was constructed 30 years ago to prevent seawater coming into the lake. The depth profile of beta-carotene suggests that the algal biomass in the lake decreased 30 years ago, being consistent with the period of the construction of the lock gate, and then increased with the increase of freshwater phytoplankton such as blue-green algae.Depth profiles of carotenoids, chlorophylls and the related pigments in the sediments of southern basin of Lake Baikal were analyzed. The photosynthetic pigments were found to be preserved through the sediment cores which spanned several hundred years. Pigments originated from green-algae, diatoms, Cryptophyceae and cyanobacteria were abundant in the sediments and major part of chlorophyll a and b were preserved as pheophytin. Biogenic perylene was detected throughout the core layrs and its presence indicates that the sediment has been under an anoxic condition.Picocyanobacteria, Synechocystis limnetica have been observed in Lake Baikal during the summer. Pigment compositions of picocyanobacteria, Synechococcus spp. and Synechocystis spp. in freshwater was studied, and the distribution and contribution of picocyanobacteria in Lake Baikal on Augest 1994 was estimated.