Algal bloom monitoring August 13, 2020: Varying amounts of cyanobacteria observed in both sea areas and lakes

Press release 2020-08-13 at 12:45
Satellite observation of the Baltic Sea on Monday 10th of August. Algae have been observed as localized surface accumulations and mixed in the water column in the open sea areas of the Bothnian Sea and the Gulf of Finland. No marked algae accumulations have been observed in the Archipelago Sea. Contains modified Copernicus data, SYKE (2020). See more in the TARKKA web map application.

Varying amounts of cyanobacteria have been observed in both sea areas and lakes. The warm and calm weather of last week has enabled cyanobacteria to rise to the surface water layers. Abundant surface blooms of cyanobacteria were observed in certain open sea areas last weekend, but this week these blooms have faded to some extent. In the lakes, cyanobacteria have become somewhat more abundant here and there, but the observations of cyanobacteria are still fewer than average for the season.

Read more in Finnish

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 Itä service

This summer, a website on algal bloom observations on the Itä 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 Laura Härkönen, Finnish Environment Institute SYKE, Tel. +358 295 251 009, (until 14/08)
  • Senior Research Scientist Kristiina Vuorio, Finnish Environment Institute SYKE, Tel. +358 295 251 757, (from 17/08)

Sea areas  

Cyanobacterial bloom situation

  • Senior Research Scientist Sanna Suikkanen, Finnish Environment Institute SYKE, Tel. +358 295 251 660, (until 14/08)
  • Senior Research Scientist Sirpa Lehtinen, Finnish Environment Institute SYKE, Tel. +358 295 251 353, (from 18/08)
  • Note! There is no expert from sea areas available on Monday 17th of August.

State of the Baltic Sea

  • Research Professor Markku Viitasalo, Finnish Environment Insitute SYKE, Tel. +358 295 251 742,


  • Communications Intern Iris Aarola, Finnish Environment Institute SYKE, Tel +358 295 252 189,