The Genus Woronichinia (Cyanobacteria) in Natural Lakes of Drawa National Park (Poland)

Abstract

Abstract Woronichinia Elenkin is a cyanobacteria genus characteristic of lentic ecosystems. The type species, W. naegeliana (Unger) Elenkin, often blooms in the plankton of eutrophic reservoirs but this genus also contains species sensitive to high nutrient concentrations. The study analyzed the diversity and biomass of Woronichinia in lakes in a national park, isolated from the direct impact of human activity. The lakes were in various trophic states resulting from gradual and natural changes of trophy. Trophy was assessed with the use of the trophic diatom index, according to the classification we proposed for natural lakes. The relationship between the biomass and the trophic state of lakes was investigated with the use of multivariate unconstrained analysis with supplementary variables. Five species of Woronichinia were identified in all trophic types of lakes except for two oligotrophic ones: W. compacta (Lemmerm.) Komárek & Hindák, W. delicatula (Skuja) Komárek & Hindák, W. karelica Komárek & Komárk.-Legn., W. obtusa Joosten and W. naegeliana (Unger) Elenkin. The occurrence and biomass of the species were related to the trophic state of the lakes. The absence of Woronichinia in two oligotrophic lakes could be due to the high concentration of humic compounds in the sediments. The low nitrogen-to-phosphorus ratio characteristic of the oligo-mesotrophic lakes resulted in increased species diversity. The lakes’ isolation from human activity fostered the development of rare and sensitive species such as W. delicatula and W. karelica.