On Friday, Sandefjord municipality went out and advised against swimming in Lake Goksjø after the bloom of toxic algae has been observed there.
– The municipal chief advises against swimming and other activities that involve exposure to water splashes or contact with the water where there is visible bloom of algae. Dogs should also not bathe or drink the water, the municipality stated, which assumes that it is blue-green algae, or cyanobacteria, writes the municipality.
However, the lake in Sandefjord is not alone in housing these potentially toxic algae.
In a new report from the Norwegian Environment Agency, where they have examined 366 Norwegian lakes, the conclusion is that around half still have, or are at risk of developing too much algae growth.
According to the report, such blooms of cyanobacteria have now been found in 30 lakes.
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Dogs died
These algae can develop two types of poison, senior adviser in the water section of the Norwegian Environment Agency, Helga Gunnarsdottir, informs Dagbladet.
– One variant can be harmful to the nervous system and the other to the liver, she says.
Last year, two dogs died after swimming in Akersvannet in Vestfold, and it is assumed that they had ingested poison that affected the liver, Gunnarsdottir states.
Domestic livestock have also died after drinking toxic water, according to the Norwegian Environment Agency.
– It is very serious when the development has come so far that toxic cyanobacteria destroy the ecosystem, and lead to people not being able to swim and enjoy the summer in their immediate environment, says director of the Norwegian Environment Agency, Ellen Hambro in a message to Dagbladet.
In both humans and animals, it has been documented that toxins from cyanobacteria can be harmful to the nervous system and liver, and in the worst case lead to death, it is said in the same message.
Both in 2019 and 2021 beaches at Lake Mjøsa were closed as a result of strong blooms of cyanobacteria. In Hålandsvatnet near Stavanger, there have been blooms of toxic cyanobacteria every summer since 2005, according to the directorate.
WARNING: At Kolbotnvannet in Nordre Follo, the municipality recommends not bathing due to the growth of cyanobacteria. oto: Nordre Follo kommune
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Deterioration
Senior adviser Gunnarsdottir says it is worrying that they do not see any clear signs of improvement in several of the investigated lakes.
– In several places there is a deterioration, she says.
– The Norwegian Environment Agency has been concerned that we do not see enough improvement in the lakes despite measures within sewage and agriculture, says environmental director Hambro in the report.
The new report has been commissioned as part of the government’s increased efforts to combat over-fertilization, and the Norwegian Institute for Water Research (NIVA) has prepared it on behalf of the Norwegian Environment Agency.
– Among other things, we will use it to point out areas where it is particularly important that measures are implemented, says Hambro.
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Poor ecological condition
The nutrients phosphorus and nitrogen from sewage and agriculture are important sources of algal blooms in Norwegian lakes, which can be unfortunate for both drinking water, bathing water, fish and other life in the lake, according to the Norwegian Environment Agency.
Many of the lakes surveyed are located in agricultural areas, cities or towns, and the new report concludes that about half are in poor ecological condition.
Most of these lakes are located in the precipitation fields that drain to the Oslo Fjord, as well as in the water regions Rogaland and Vestland.
Collapse in the ecosystems along the Norwegian coast
– Measures work
Senior adviser Helga Gunnarsdottir points out that not everything is completely black.
– There are also some gratifying results in the report. In Haldenvassdraget, Vansjø-Hobølvassdraget or on Jæren, where the municipalities and local farmers have worked systematically and purposefully within drainage measures and agricultural measures, such as reduced fertilization, you see an effect in many lakes, she says.
– The measures work if they are implemented at the same time, she adds.
- In 125 of the lakes in the study, the researchers looked at the development in phosphorus and algae growth over a 12-year period.
- While 70 of these show neither improvement nor deterioration, a deterioration is seen in 22 of the lakes.
- These include lakes in Follo, Indre Oslofjord Vest, on Hadeland, individual lakes around Lake Mjøsa, and in the water areas Aulivassdraget, Horten-Larvik and Numedalslågen in Vestfold and Telemark, the Norwegian Environment Agency informs.
- In 33 of the other lakes where NIVA has looked at the development over time, there is an improvement, in that there is either less algae growth, less phosphorus or less of both.
- As many as 15 of these lakes are located in either the Halden watercourse, the Vansjø-Hobølv watercourse or on Jæren.
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