The influence of climate factors on the presence of microcystins in freshwaters – a case study from Poland

Climate changes are expressed as increase of temperature and the frequency and intensity of severe weather conditions. Furthermore, climate change promotes development of bloom-forming cyanobacteria and the increase the intensity and toxicity of the blooms. According to European Environmental Agency (EEA), Europe is the fastest warming continent and particularly high warming is found over eastern Europe. The last six years were recognized as the warmest on record. However, the greatest changes will be possible to identify locally. We conducted the short-term surveys of concentrations of microcystins, which are recognised as the most often produced cyanotoxins, in two shallow and small water bodies in southern Poland. Data was collected during four years of monitoring: 2017, 2019-2021. We hypothesised that microcystin concentration is related to weather conditions. The pattern of microcystins distribution during the seasons were similar in both of them: toxins were present from July to October. Statistical analyses showed that significant factor correlated with concentration of microcystins was rainfall higher than 2.2 mm. Besides, stepwise regression demonstrated that rainfalls and air temperatures were significant contributors for dimensions PCAI and PCAII, which cumulatively explained 53% of variance