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Swimming water quality and blue-green algae

Swimming water quality

The hygienic quality of swimming water in the beaches of Helsinki is assessed by studying the prevalence of intestinal enterococci and Escherichia coli, sampling plan (pdf) during the bathing season (15.6.-31.8.). The amount of blue-green algae is assessed organoleptically in connection with the sampling.

Water samples taken in previous years have at times shown elevated levels of enteric bacteria in Marjaniemi, Pikkukoski, Tapaninvainio and Pakila beaches. It is normal for the quality of natural water to vary, but water quality may occasionally decline considerably at Marjaniemi beach. The cause of impaired water quality is still unclear and is being investigated.

In beaches of Pikkukoski, Tapaninvainio and Pakila water quality will decline following heavy rains when rainwater flushes microbes from the ground into the water.

City of Helsinki Environmental Services recommends avoiding swimming at Marjaniemi beach in summer 2022 and in Pikkukoski, Tapaninvainio and Pakila during the heavy rains. Water quality monitoring will be enhanced in these beaches summer 2022.

You can find information on the beaches in the metropolitan area, for example the algae situation and the water temperature, in the Outdoor Exercise Map. 

Swimming water quality classification

The water quality of the large public beaches of Helsinki was categorised into four categories (excellent, good, adequate and poor. The classification is affected by the amounts of intestinal enterococci and Escherichia coli found in the samples. The classifications are updated annually.

Swimming Water Quality Classification, Helsinki

Blue-green algae

The amount of blue-green algae usually starts to increase in July and peaks at the turn of July and August. Blue-green algae are visible in the water as small amounts of greenish or yellowish sticks or nuggets. Large amounts of blue-green algae may gather on the water’s surface into algal blooms. Algal mass that ends up on a shore may resemble thick paint or pea soup. Blue-green algae typically have a mouldy, soil-like smell.

Swimming in water in which blue-green algae has been observed should be avoided. Small children should not be let into the water during blue-green algal blooms, as they might ingest water that contains blue-green algae. Water that contains blue-green algae should also not be used for washing or as sauna water. If you wish to swim despite the occurrence of blue-green algae, you should wash up with clean water immediately after swimming.

Blue-green algae may produce toxic or irritating substances in the water. Blue-green algae have been known to cause rashes, irritation of the eyes and fevers, among other symptoms.

More information

In the Outdoor Exercise Map service you can find information on the beaches in the metropolitan area – the algae situation and the water temperature. 

Questions about water quality on public beaches:

12.07.2022 12:14