Increased risk of exposure to microcystins in the scum of the filamentous cyanobacterium Aphanizomenon flos-aquae accumulated on the western shoreline of the Curonian Lagoon

[Display omitted] •Cyanotoxins concentration increases by up to 300-fold in the near-shore waters.•First report on the toxic blooms of Planktothrix agardhii in the Curonian Lagoon.•Removal of cyanobacteria scums in the Curonian Lagoon has to be prioritised. Concentration of toxic cyanobacteria blooms on the downwind shore of high recreational amenity water bodies with largely increases the risk of exposure to cyanotoxins. In this study analysis of phytoplankton structure, cyanotoxin composition and concentration was performed on cyanobacteria scum material, high- and low-density bloom samples in the Curonian Lagoon. We found that the concentration of cyanotoxins in the scum material increased from ∼30 to ∼300-fold compared to bloom samples. In Microcystis aeruginosa dominated samples microcystin-LR was present at the highest concentration, while the dominance of Planktothrix agardhii was associated with the occurrence of dmMC-RR as the major microcystin variant. The toxicological potential of cyanobacterial scums in the Curonian Lagoon is emphasized, and management by removal of these scums is proposed.