Role of Environmental Factors and Toxic Genotypes in the Regulation of Microcystins-Producing Cyanobacterial Blooms

Abstract

The aim of this study was to understand: (1) how environmental conditions can contribute to formation of Microcystis-dominated blooms in lowland, dam reservoirs in temperate climate-with the use of quantitative molecular monitoring, and (2) what is the role of toxic Microcystis genotypes in the bloom functioning. Monitoring of the Sulejow Reservoir in 2009 and 2010 in two sites Tresta (TR) and Bronislawow BR), which have different morphometry, showed that physicochemical conditions were always favorable for cyanobacterial bloom formation. In 2009, the average biomass of cyanobacteria reached 13 mg L(-1) (TR) and 8 mg L(-1) (BR), and in the second year, it decreased to approximately 1 mg L(-1) (TR and BR). In turns, the mean number of toxic Microcystis genotypes in the total Microcystis reached 1% in 2009, both in TR and BR, and in 2010, the number increased to 70% in TR and 14 % in BR. Despite significant differences in the biomass of cyanobacteria in 2009 and 2010, the mean microcystins (MCs) concentration and toxicity stayed at a similar level of approximately 1 μg L(-1). Statistical analysis indicated that water retention time was a factor that provided a significant difference between the two monitoring seasons and was considered a driver of the changes occurring in the Sulejow Reservoir. Hydrologic differences, which occurred between two studied years due to heavy flooding in Poland in 2010, influenced the decrease in number of Microcystis biomass by causing water disturbances and by lowering water temperature. Statistical analysis showed that Microcystis aeruginosa biomass and 16S rRNA gene copy number representing Microcystis genotypes in both years of monitoring could be predicted on the basis of total and dissolved phosphorus concentrations and water temperature. In present study, the number of mcyA gene copies representing toxic Microcystis genotypes could be predicted based on the biomass of M. aeruginosa. Moreover, MCs toxicity and concentration could be predicted on the basic of mcyA gene copy number and M. aeruginosa (biomass, 16S rRNA), respectively. Present findings may indicate that Microcystis can regulate the number of toxic genotypes, and in this way adjust the whole bloom to be able to produce MCs at the level which is necessary for its maintenance in the Sulejow Reservoir under stressful hydrological conditions.

Relationships among cyanobacteria, zooplankton and fish in sub-bloom conditions in the Sulejow Reservoir

“…2) and even though significantly higher concentrations of toxic genotypes of cyanobacteria were found in July (P<0.001 for mcyA). Similar relationships have previously been observed in the Sulejow Reservoir, when, due to a decrease in Microcystis biomass as a result of poor growing conditions (short retention time), the amount of toxic genotypes increased (Gągała et al, 2014). In 2013, the cause of the observed phenomena could be analogous, because the reported retention time was almost twice as short in July as it was in September (18.8 and 23.1 days on 16 and 18 July and 32.4 and 34.0 days on 23 and 25 September, respectively; data from The Regional Water Management Authority in Warsaw, www.warszawa.rzgw.gov.pl).…”

“…and Aphanizomenon flos-aquae (L.) (Izydorczyk et al, 2008). The dominant species of bloom-forming cyanobacteria is M. aeruginosa, which produces microcystin-LR (MC-LR), microcystin-YR (MC-YR) and MC-RR (Jurczak et al, 2005;Gągała et al, 2014 (Frankiewicz et al, 1999;Frankiewicz and Świerzowski, 2004).…”

“…The qRT-PCR analyzes for 16S rRNA and mcyA were prepared according to Gągała et al (2014). Each reaction was performed in a final volume of 25 µL.…”

Using Chemically Treated Organic Recycling Materials to Enhance Freshwater Purification

“…The ratio of the mentioned ions to phosphorus could be easily changed and controlled in streams and drainage ditches by applying tested deposits. The achieved level of phosphate reduction, combined with the low cost of producing the deposit using the new device (about $80 per ton of deposit) and the use of waste materials, makes the technology widely applicable and complementary to other methods for reducing phosphate pollution and preventing cyanobacterial blooms in reservoirs [40][41][42][43]. Another feature that is extremely important from the point of view of sustainable development is that the chemical deposits are formed only from natural, biodegradable fibrous raw materials.…”

Mass development of phytoplankton in the River Warta in Poznań (Poland) in the 21st century

“…Cyanobacteria blooms have been observed in numerous lakes and reservoirs in Poland (Zagajewski et al 2007;Grabowska and Mazur-Marzec 2011;Mankiewicz-Boczek et al 2011;Kobos et al 2013;Gągała et al 2014) and many other countries around the world (Carmichael 2008;Merel et al 2013). They have also been noted in eutrophic rivers, e.g.…”