Phytoplankton composition with an emphasis of Cyanobacteria and their toxins as an indicator for the ecological status of Lake Vaya (Bulgaria) – part of the Via Pontica migration route

Abstract

As producers of biomass, cyanobacteria are a major part of the phytoplankton in a large number of water basins. Due to the cyanobacterial blooms and cyanotoxins produced, these organisms are recognized as a threat and ecological risk for water bodies. Released cyanotoxins may cause death of many organisms including birds and fish. Vaya Lake is the largest natural lake in Bulgaria. It is located on the Via Pontica migration route of birds between Europe and Africa. Since 2003, the lake has been declared as a "Wetland of international importance” under the Ramsar Convention. According to the literature data from 2002-2006, the Lake is defined as highly eutrophied due to strong anthropogenic pressure, but regular monitoring of the cyanobacterial blooms and presence of cyanotoxins after this period is missing. Taking into account the importance of this unique, protected ecosystem, our aim was to make a complete ecological assessment of the present state of Lake Vaya by using the phytoplankton, with an emphasis on cyanobacterial blooms and the presence of cyanotoxins. As results of the study, we 1) characterized the phytoplankton composition qualitatively and quantitatively; 2) evaluated the ecological status of the western and eastern part of the Lake; 3) identified the potential producers of cyanotoxins; 4) observed cyanobacterial blooms and discussed the influence of macrophytes on their spread; 5) measured the concentrations of the cyanotoxins MCs, CYL and STXs in water samples from both parts of the Lake. Our results indicated the need for continued observation of cyanobacterial composition, blooming and the presence of cyanotoxins in Lake Vaya.

Empirical testing of cryoconite granulation: Role of cyanobacteria in the formation of key biogenic structure darkening glaciers in polar regions

“…The calyptra was weakly expressed. During microscopic inspection of fresh and old cultures, we did not see multiple trichomes in a common sheath—the feature characteristic for Microcoleus vaginatus (Strunecký et al, 2013) but not obligatorily present in strains (Teneva et al, 2023). Taxonomic revision of the genus Microcoleus is needed, especially given the high diversity and wide distribution of strains and the existence of numerous lineages in which new species could be present (Stanojković et al, 2022).…”

“…The pictures were taken weekly for 12 weeks. [Color figure can be viewed at wileyonlinelibrary.com] (Strunecký et al, 2013) but not obligatorily present in strains (Teneva et al, 2023). Taxonomic revision of the genus Microcoleus is needed, especially given the high diversity and wide distribution of strains and the existence of numerous lineages in which new species could be present (Stanojković et al, 2022).…”

“…Taxonomic identification of strains was based on a combination of molecular marker (16S rRNA gene sequencing; for methods of DNA extraction, amplification, and phylogeny see Appendix S1 in the Supporting Information). Microscopic observations of filaments and identification of their key morphological features were according to Komárek and Anagnostidis (2005), Teneva et al (2023), and Strunecký et al (2011, 2013).…”

Allelopathic Potential of the Cyanotoxins Microcystin-LR and Cylindrospermopsin on Green Algae

“…It has been reported that cyanobacteria are a dominant group in many water bodies [ 56 , 57 , 58 , 59 , 60 , 61 ]. In some water bodies, there is even a displacement of the Chlorophyta, which traditionally occupy the first place in the phytoplankton of freshwater basins, by representatives of cyanobacteria [ 57 , 60 , 62 ]. In all cases, however, the representatives of these groups of phytoplankton interact with each other and cyanobacteria always have an advantage.…”