Diversity and toxin content of cyanobacteria in fish ponds (South Moravia, Czech Republic) related to fishery management intensity

Abstract

During the vegetative period of the year 2005 (June–October) we carried out hydrobiological and hydrochemical monitoring of selected ponds inhered in Southern Moravia in relation to different fi­she­ry management intensities. Water temperature, dissolved oxygen content, pH, conductivity and water transparency were monitored directly at taking place, N–NH4+, N–NO2-, N–NO3-, P–PO43- content and chlorophyll-a concentration were measured in hydrochemical laboratory. At the same time, water samples for taxonomical analyses of phytoplankton and assessment of toxin content of cyanobacteria were taken. All ponds were characterized by low water transparency, high values of pH, N–NH4+, P–PO43- and high chlorophyll a concentration. We detected maximum concentration of 18.7 µg . l−1 microcystins in ponds dominated by the species Microcystis aeruginosa. Total microcystin concentration in water of all ponds with dominance of pikoplanktonic cyanobacteria were below detection limit (LOD < 0.125 µg . l−1). The dominance of cyanobacteria species shifts from coccal (especially genus Microcystis) to small-colonial pikoplanctonic (genus Aphanocapsa, Aphanothece) and to single-filamentous (genus Planktothrix, Limnothrix, Pseudanabaena) cyanobacteria related to increasing fish stock density.

Keywords

• cyanobacteria
• ponds
• fish stock
• microcystins