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Algal bloom monitoring June 4, 2020: Some cyanobacterial blooms in the sea areas, scarce observations of cyanobacterial blooms in lakes

Press release 2020-06-04 at 15:54
© Ilkka Lastumäki / itameri.kuvat.fi

The Finnish Environment Institute SYKE has started this week its cyanobacterial bloom reporting for the summer 2020. In the Finnish sea areas some cyanobacteria have been observed locally. In lakes, observations of scarce amounts of cyanobacteria have been made only at two locations. In near-shore waters, yellowish pine pollen that misleadingly resembles cyanobacteria may occur. Citizens can participate in the cyanobacterial monitoring during the summer by using the Havaintolähetti mobile phone application or by setting up their own observation spot in the Järvi-meriwiki internet service. SYKE will produce weekly reports on the algae situation until the end of August. SYKE has also today published a risk assessment of cyanobacterial blooms in the Finnish sea areas in summer 2020.

Cyanobacterial blooms observed in the Finnish sea areas in some places

There is a normal early summer situation in the Finnish sea areas; in other words, no significant and widespread cyanobacterial blooms have yet been observed. Some cyanobacterial blooms have been observed in places on the southern and south-western coasts of Finland and in the high seas of the Gulf of Finland.

“Pine pollen, which deceptively looks like cyanobacteria, may also be found in places. If there is pollen in the water, it is usually also found on dry land, such as on piers and yard furniture,” says researcher Heidi Hällfors from the Finnish Environment Institute.

Some cyanobacteria species are able to bloom even in cold water and during winter. Still, the amount of cyanobacteria usually only increases in July as the surface temperature of seawater exceeds about 16–17 degrees. At the moment, the temperature of seawater in the Finnish sea areas varies from 5 to 14 degrees. The actual surface bloom of cyanobacteria usually requires at least a couple of weeks of favourable temperature, wind, and light conditions to develop.

Scarse cyanobacterial blooms in lakes

So far, very little blue-green algae have been observed in lakes, which is a typical situation in early summer. Minor cyanobacterial blooms have been detected at only two national algal monitoring sites. Abundant or very abundant surface blooms of cyanobacteria have not been observed in lakes. In early summer, conifer pollen can form yellowish floating masses on shores.

"Cyanobacteria occur in all types of lakes, but surface blooms typically occur in eutrophic lakes with enough nutrients for algal growth. In addition to nutrients and water temperature, the growth of cyanobacteria and the formation of blooms are influenced by many factors, which makes it difficult to predict the development of the cyanobacterial blooms in a single lake", says researcher Kristiina Vuorio from Finnish Environment Institute

Surface blooms typically form during warm and calm periods. The abundant occurrences of cyanobacteria in the lakes typically occur in July and August. If warm weather occurring in the beginning of June continues, it can bring forward the increase in cyanobacteria in lakes. In addition, the mild and rainy winter has brought a high nutrient load to the lakes, which can contribute to the formation of cyanobacterial blooms.

The surface temperatures of the lakes are currently typical of the time. The surface water temperature in lakes of the southern and western part of Finland is 14–18 degrees, in the central and eastern part of the country and in Kainuu mainly 12–14 degrees. The lakes of northern Lapland are still frozen.

SYKE observes the cyanobacteria occurrence as part of the monitoring of the state of the environment

The national cyanobacterial monitoring is based on the monitoring of algal deposits in surface water, and the intention is to provide an overview of the cyanobacterial situation in different water bodies. Observations are carried out as part of the monitoring of the state of the environment in cooperation with the Centres for Economic Development, Transport and the Environment, municipal environmental and health authorities and the Finnish Environment Institute.

This summer, Finnish Rotary Clubs will also be actively involved in cyanobacterial monitoring. As a consequence, the number of observation points on the southwestern and southern coasts of Finland will increase by about 100 observation points. The involvement of the Rotary Clubs makes it possible to re-introduce the sea algae barometer in addition to the lake algae barometer on the Järvi-meriwiki (Lake and sea wiki) service. The algae barometer can be used to compare the algae situation this summer with that of previous years.

Algal bloom monitoring includes almost 400 permanent observation sites across the country on inland and coastal waters and in the archipelago. Information on the cyanobacterial situation in the high seas is available, for example, from satellite images, the Finnish Border Guard, research vessel Aranda as well as cruise and merchant ships (MS Finnmaid and MS Silja Serenade) which are equipped with the Algaline measuring equipment.

The Finnish Environment Institute reports on the cyanobacterial situation on a weekly basis every Thursday from the beginning of June until the end of August. For marine areas, the information mainly concerns high seas areas. The weekly algal reporting related to the national cyanobacteria monitoring started 22 years ago, in 1998.

Several compounds produced by cyanobacteria can cause health hazards

According to the guidelines of the National Institute for Health and Welfare (THL), water rich in cyanobacteria should always be treated in such a way that it may be harmful to health. Cyanobacteria produce a number of different compounds that can cause symptoms. Some cyanobacteria can produce liver or nerve toxins, but most of the symptoms experienced by swimmers may also be due to other compounds.

Especially small children and pets should be kept out of water rich with cyanobacteria. Water with cyanobacteria should not be used in the sauna or as washing or irrigation water. If poisoning is suspected, seek medical advice or take your pet to a veterinarian. If necessary, the Poison Information Centre will provide additional instructions.

The municipal health authorities monitor the cyanobacterial situation on the beaches.

Report your algal bloom observations to the Järvi-meriwiki (Lake and sea wiki)

In the Järvi-meriwiki maintained by the Finnish Environment Institute, everyone has the opportunity to establish their own observation site and share algal bloom observations from lakes and coastal areas. Individual observations can also be sent while navigating different water bodies. You can also report observations using the smartphone-friendly Havaintolähetti website. The reported observations are shown on the national algal situation map, and they support the national algal situation assessment. Observations about the absence of cyanobacteria are also important.

Järvi-meriwiki is an online service produced in collaboration with authorities and citizens. The service provides basic information on all lakes larger than one hectare as well as different areas of the Baltic Sea. Users can share, for example, photos and other observations on the service.

Municipalities and cities monitor the cyanobacterial situation on the beaches, so it is advisable to report rich cyanobacterial blooms on beaches to the health authorities of the municipality in question.

Cyanobacteria observations also in the Itämeri.fi service

This summer, a website on algal bloom observations on the Itämeri.fi service is also launched. The cyanobacterial map presented on this algal bloom observations page combines the observations reported to the Järvi-meriwiki and from the beaches of the City of Helsinki as well as the observations based on satellite interpretations of the Finnish Environment Institute during the last three days.

This is how you identify cyanobacteria

A small amount of cyanobacteria in the water appears as green or yellowish particles. Narrow stripes of algae can drift to a beach. In calm weather, a substantial amount of cyanobacteria forms greenish or yellowish algal rafts and piles up in coastal water. Unlike cyanobacteria, pollen is found not only on the surface water but also, for example, on piers or yard furniture.

If the algae dissolve into tiny particles in the water when you touch it with a stick, it may be cyanobacteria. If the algae attache to the stick, it is something other than cyanobacteria. In a glass of water, cyanobacteria rise to the surface as tiny greenish particles within about an hour.

Algae bloom risk analysis

The risk of cyanobacterial blooms in the Finnish sea areas is considerable or moderate – the summer weather determines the actual situation (Press release June 4, 2020)

Information about algae situation 


More information

(Telephone 1.00-3.00 pm)


  • Researcher Kristiina Vuorio, Finnish Environment Institute SYKE, Tel. 0295 251 757, firstname.lastname@ymparisto.fi

Sea areas

Cyanobacterial bloom situation

  • Researcher Heidi Hällfors, Finnish Environment Institute SYKE, Tel. 0295 251 114, firstname.lastname@ymparisto.fi

State of the Baltic Sea

  • Head of Unit Harri Kuosa, Finnish Environment Institute SYKE, Tel. 0295 251 106, firstname.lastname@ymparisto.fi  (till June 5)
  • Research Professor Maiju Lehtiniemi, Finnish Environment Institute SYKE, Tel. 040 5034 356, firstname.lastname@ymparisto.fi (from June 8)


  • Communication Specialist Hannele Ahponen, Finnish Environment Institute SYKE, Tel +358 50 327 5997, firstname.x.lastname@ymparisto.fi

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