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

Szeląg-Wasielewska E.

Oceanological and Hydrobiological Studies

2010

Vol. 39, No.2

121-133

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.

Auto- and heterotrophic picoplankton in a lowland river (Warta River, Poland)

Szeląg-Wasielewska E., Stachnik W.

Oceanological and Hydrobiological Studies

2010

Vol. 39, No.1

137-146

The structure of plankton in a lowland river was studied with a particular focus on autotrophic as well as heterotrophic picoplankton cells. Water samples were collected in the middle, meridional section of the Warta River in 2005. Heterotrophic picoplankton (HPP) were represented by bacteria varying in size and form, but mainly by cocci and rods. HPP abundance ranged from 3.5 × 10^6 to 9.5 × 10^6 cells m1^-1. Autotrophic picoplankton (APP) densities were considerably lower and ranged from 1.2 × 10^3 to 92 × 10^3 cells ml^-1. They were represented by prokaryotes (picocyanobacteria) and eukaryotes (small chlorophytes). Both components occurred together but eukaryotic APP usually prevailed in terms of biomass. In terms of biomass, APP seemed to play a minor role in this ecosystem in comparison with heterotrophic picoplankton.

The smallest phototrophic organisms in a lowland river: comparison with other components of the phytoseston

Szeląg-Wasielewska E.

Oceanological and Hydrobiological Studies

2004

Vol. 33, No. 4

61--72

The phytoseston of the Warta, a polluted eutrophic river in western Poland, was studied from spring to autumn 2003. The focus of the study was autotrophic picoplankton (APP). APP abundance fluctuated from 1.3×10sup>6 to 1.05×10sup>8cells Lsup>-1 and was characterized by a maximum in late July. APP biomass was low, ranging from 0.5 to 19.7μg C Lsup>-1. Both cyanobacteria and eukaryotic organisms were found within the picoplankton. The picocyanobacterial community was often dominated by colonial forms, mostly Aphanocapsa spp. and Cyanogranis ferruginea (Wawrik) Hindák. Eukaryotic picoplankton included chlorophytes of the genera Chlorella, Choricystis, and Pseudodictyosphaerium jurisii (Hindák) Hindák. Among the phytoplankton larger than 2 μm, the most abundant species were diatoms and chlorophytes, except in late August, when filamentous cyanobacteria dominated. The contribution of APP to the total phytoplankton biomass was usually below 1%, and the mean (0.6%) was close to the lower limit of values found in lakes.