The calm and warm weather has meant that cyanobacteria (algae) have formed surface accumulations in large parts of the Baltic Sea.

- We have observations that the algae are approaching the coast more and more, says Lisa Lind oceanographer at SMHI.

Gotland's most affected

It is still so far Gotland and especially Fårö that is most affected by the algae.

- Gotland is most affected but we have also made observations on Stora Gåsskär in the St Anna archipelago. What can stop increased algal blooms is that we get cooler weather in the future, says Lisa Lind at SMHI.

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With the heat comes the algal bloom - expected to pick up speed in the next few days Photo: TT archive / SVT