title: Mass Development of Diazotrophic Cyanobacteria (Nostocales) and Production of Neurotoxic Anatoxin-a in aPlanktothrix(Oscillatoriales) Dominated Temperate Lake.
abstract: In spite of extensive studies on multispecies toxigenic cyanobacterial blooms, they are still difficult to eliminate, and factors regulating their succession and toxin production remain still to discover. A 4-year study revealed periodical mass development of diazotrophicNostocalessuch asDolichospermumspp. (previouslyAnabaena),Aphanizomenon gracileand expansiveCuspidothrix(previouslyAphanizomenon)issatschenkoiin a lake affected by perennial blooms ofPlanktothrix agardhii(Oscillatoriales). Compared toOscillatoriales,Nostocalesreached the highest total biomass (up to 16 mg L-1) and contributed nearly 33-85 % to the total biomass of filamentous cyanobacteria at higher water temperatures (average values 17.5-22.6 °C) and higher ratio (11.8-14.1) of dissolved inorganic nitrogen to dissolved inorganic phosphorus (DIN/DIP). Species structure ofNostocaleschanged considerably from year to year as indicated by the Jaccard similarity index (0.33-0.78). Concentrations of intracellular anatoxin-a (ANTX) ranged from 0.03 to 2.19 μg L-1of the lake water, whilst extracellular toxin reached up to 0.55 μg L-1. The highest positive correlations were found between the intracellular ANTX and the biomass ofDolichospermumspp. (R2= 0.73) andC. issatschenkoi(R2= 0.43-0.65). Our study suggests that ANTX production byDolichospermumdepended mainly on water temperature, whereas that byC. issatschenkoiwas related to water conductivity and DIN/DIP ratio. P-PO4concentrations also seemed to be important. The relatively short-term mass development of neurotoxicNostocalesis an additional threat to shallow, highly eutrophic water bodies continuously affected byOscillatorialesblooms and may be controlled mainly by the DIN/DIP ratio. ANTX should be considered as a pollutant of freshwaters.
authors.affiliation: Department of Hydrobiology, University of Life Sciences in Lublin, Akademicka 13, 20-950 Lublin, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Toporowska
authors.affiliation: Department of Hydrobiology, University of Life Sciences in Lublin, Akademicka 13, 20-950 Lublin, Poland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Pawlik-Skowrońska
authors.affiliation: Centre for Ecological Research, P.A.S., Experimental Station, Niecała 18, 20-080 Lublin, Poland.
authors.forename: Renata
authors.initials: R
authors.lastname: Kalinowska
keywords: Anabaena; Anatoxin-a; Aphanizomenon issatschenkoi; DIN/DIP ratio; Hypertrophic lake; Nutrients