Vertical Distribution and Migration of Algae under Thermal Stratification in Small Water Bodies of the Forest-Steppe Volga Region

Abstract

In this article the author presents some study results of taxonomic composition, distribution and migrations of algae under thermal stratification in small water bodies of the forest-steppe Volga region. The author considers the main factors influencing the formation of heterogeneity of the structure of algocoenoses: vertical temperature gradients, water density and the content of basic biogenic substances. The composition of vertically migrating common species is discovered. The nature of species distribution during the day is shown, when samples are taken with an interval of 3 hours. The predominance of mobile mixotrophic phytoflagel-lates is a feature of the taxonomic composition of algae in water bodies with a pronounced vertical heterogeneity of populations of dominant species. The clearest picture of distribution and migration in plankton is demonstrated by Pandorina morum, Mallomonas caudata, Dinobryon divergens, Cryptomonas curvata, and a number of other large-cell flagellar forms. Of the species without active movement, vertical distribution was constantly observed in Westella botry-oides, Botryococcus braunii, Dictyosphaerium pulchellum, Koliella longiseta, Woronichinia naegeliana, and some species of the genus Anabaena. The author notes the connection between the maximums of the abundance of some common species with changes in the content of nutrients within the photic zone. Vertical heterogeneity of taxonomic and quantitative indicators in algocoenoses is considered as an adaptive strategy to the heterogeneity of the habitat in highly eutrophic water bodies with a high density of algae in plankton.