AME prepress abstract  -  doi: 10.3354/ame01194

ABSTRACT: 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 realised. Thirty water samples were taken from 11 water bodies, of which 18 were obtained from the Sulejow Reservoir during a regular monitoring from June to October. Intra- and extracellular MC concentrations in Sulejow samples were measured by High Performance Liquid Chromatography (HPLC). The extracellular MC concentration was assessed using 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 chl a, temperature). In Sulejow, high intracellular MC concentrations corresponded to large cyanobacterial biovolumes and to low TN/TP ratio. 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 two different Operational Taxonomic Units (OTU) 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, 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.