Finnhällan ligger några kilometer väst om Boviksbadet.
The County Administrative Board's Information Center for the Bothnian Bay (ICBV) received two reports of suspected algal blooms on Thursday, one from Piteå and one from Finnhällan, off the coast of Skellefteå.
At Finnhällan, about half a mile west of Boviksbadet, "clear light green accumulations" were visible on the water. A sample has been taken and will be analysed next week.
The ICBV is advising the public to avoid contact with the water. "It is especially important not to let children swim, as they can swallow the algae and become seriously ill," the information center writes. Dog owners should also keep their dogs away from the water, as they can ingest larger amounts of algae by drinking the water or licking their fur and paws after being in the water.
SMHI's monitoring of the algal situation through satellite images shows that there are surface accumulations of algae in the open sea in the Gulf of Bothnia. These are not yet drifting significantly, but may start to drift towards the coast in the future.
The observation in Piteå was made at Svartnäsudden, where the water was clearly green-tinted on Wednesday evening. Most of it had disappeared by the following day. During the week, there were also reports of algae blooms at Borgasand in Sundsvall municipality.
Algae blooms occur both at sea, along the coast and in lakes and waterways. They occur mainly in late summer and fall. Certain types of phytoplankton and cyanobacteria produce toxins. One example is the cyanobacterium, or cat hair algae, which is common in the Baltic Sea and the Gulf of Bothnia.