Vertical distribution of phototrophs in the pelagic zone of three small Lobelia lakes

Abstract

Vertical distribution of phototrophs in the pelagic zone of three small Lobelia lakes The community structure and biomass of pelagic phototrophs, with a particular focus on the picoplanktonic fraction, were studied in three small, soft-water lakes in the Pomerania Lake District (north Poland). The smallest phototrophs were usually dominated by picocyanophytes, both single-celled and colonial. Picochlorophytes were less frequent, and they formed dense populations only in one lake. The nano- and microplankton included many groups of organisms, but the main groups were comprised of dinoflagellates, chrysophytes and chroococcoid and/or filamentous cyanophytes and large raphidophytes. Community structure changed significantly with depth and in all lakes remarkable differences were observed between the epilimnion and both the meta- and hypolimnion. The hypolimnion was characterized by the presence of photosynthetic green sulfur bacteria or their symbiotic consortia.