Abstract :
[en] Microscopic measurements of fresh biomass and 16S rRNA gene sequences from clone
libraries and denaturing gradient gel electrophoresis (DGGE) were used to investigate cyanobacterial
diversity in Polish water bodies in 2002. In addition, measurements of microcystin (MC) concentrations
were made. Thirty water samples were taken from 11 water bodies; of these samples,
18 were obtained from the Sulejow Reservoir during regular monitoring from June to October. Intraand
extracellular MC concentrations in Sulejow samples were measured by high performance liquid
chromatography (HPLC). The extracellular MC concentration was assessed using a protein phosphatase
inhibition assay (PPIA) in additional lakes. Additionally, physicochemical parameters were
measured (total nitrogen [TN], total phosphorus [TP], TN:TP ratio, chlorophyll a concentration,
temperature). In Sulejow, high intracellular MC concentrations corresponded to large cyanobacterial
biovolumes and to low TN:TP ratios. In the other lakes, extracellular MCs were not linked to any
measured parameters. The combination of the microscopic and molecular data showed that Aphanizomenon
and Microcystis were the dominant genera during the summer period in the Sulejow Reservoir.
At the genetic level, there was a succession of 2 different operational taxonomic units (OTUs)
belonging to the lineage Anabaena/Aphanizomenon. In the other water bodies, the most frequent
populations were Aphanizomenon, Anabaena, Microcystis and Planktothrix. Small populations of
Romeria, Snowella, Woronichinia, Limnothrix and Pseudanabaena were observed, and an enigmatic
cluster affiliated with Prochlorothrix was genetically retrieved. Anabaena and Microcystis were
presumed to be the main genera responsible for the MC production.
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