Are there concerns regarding cHAB in coastal bathing waters affected by freshwater-brackish continuum?

Are the existing guidelines sufficient for the assessment of bathing water quality? The example of Polish lakes

“…This increase in Poland was not only related to the demand for ecosystem services of the local population due to the increasing mean temperature (especially in the summer period) but also due to changes in the law regulations related to bathing waters which encouraged the local administration, as well as private owners of water bodies, to register the bathing waters. However, climate change significantly affect the water bodies, providing optimal conditions for the occurrence of cyanobacterial blooms which are noticed more often (Paerl and Huisman 2008;Huisman et al 2018;Mantzouki et al 2018;Kataržytė et al 2019;Chen et al 2020;Overlingė et al 2020). Cyanobacterial blooms, as shown in this study, were the main reason for the closing of many bathing waters (Fig.…”

“…Moreover, the study and assessment of HAB in the Baltic Sea in the Lithuania region confirmed the presence of cyanotoxins (Overlingė et al 2020). Furthermore, as was mentioned in the "Introduction" section, the study by Kokociński et al (2013) showed that cyanobacterial cytotoxin (cylindrospermopsin) was present in almost 40% of 34 investigated lakes in western Poland.…”

“…These findings are in line with those of another study performed in Germany, in which the authors showed that cytotoxin was detected in 50% of 127 German lakes (Fastner et al 2007). Taking into account the obtained results, Overlingė et al (2020) recommend routine monitoring of cyanotoxins in the south-eastern Baltic Sea during the bathing season. Thus, the level of potentially toxic cyanobacteria in bathing waters (especially in the Baltic Sea) systematically increases, and this issue should also be addressed in other water reservoirs due to the increasing average global temperature.…”

“…3, Fig. S1 in Supplementary Materials 2; Table S1 in Supplementary Materials 1) to protect people from potentially toxic effects (WHO 2003;Poniedziałek et al 2012;Rzymski and Poniedziałek 2014;Kataržytė et al 2019;Overlingė et al 2020). However, as mentioned in the "Introduction" section, bathing waters are assessed only by microbiological contamination.…”

“…Thus, considering the higher sensitivity of small water bodies to changes in the catchment and the additional load of nutrients resulting from the recreational activities of people, small water bodies with bathing waters in particular should be additionally monitored with the obligatory assessment of chlorophyll-a concentration. This monitoring might be supported or even performed by the remote sensing methods to minimize the costs of the chlorophyll-a analysis as many authors were already suggested (Kataržytė et al 2019;Chen et al 2020;Overlingė et al 2020). As pointed above, small water bodies are especially characterized by rapid changes and the water quality might transition from good ("the clear water state") to bad ("the turbid water state") (Scheffer 1989;Scheffer and Van Nes 2007;Janssen et al 2014;Andersen et al 2020).…”