Cyanobacteria are among the oldest organisms on Earth
Cyanobacteria, also known as blue-green algae, have existed on Earth since its early days, and the oxygen released from their photosynthesis was the initial step in the formation of Earth’s atmosphere. Cyanobacteria photosynthesize like algae, but they are bacteria. Cyanobacteria can produce various toxic and otherwise harmful compounds, so all cyanobacterial blooms should be approached with caution.
Cyanobacteria (blue-green algae) are part of the phytoplankton in the Baltic Sea. Phytoplankton is responsible for the primary production in open sea ecosystems, meaning it is food for zooplankton and produces oxygen for the atmosphere. Currently, around 2,000 species of phytoplankton are known in the Baltic Sea.
There are always some cyanobacteria in the water. However, they are often only noticed when their numbers increase in the summer. In early summer, the water is often too cool for cyanobacteria, and they have to compete with other phytoplankton species.
Cyanobacteria are most abundant in the Baltic Sea in July and August when the water is warm. During this time, there is a lot of zooplankton in the water, but it does not favour cyanobacteria due to their poor nutritional value. Therefore, zooplankton does not significantly hinder the growth of cyanobacteria, which can form strong blooms. Most cyanobacteria decompose in the water, with only a small portion sinking to the bottom. Decomposing cyanobacteria can turn the shores turquoise in autumn, especially in the Gulf of Finland.
Dead cyanobacteria turn the shores turquoise
When cyanobacteria die, the decomposing cells release phycocyanin pigment, which can colour the shores bluish. This turquoise colour is especially visible in autumn along the shores of the Gulf of Finland.
Cyanobacteria have several competitive advantages compared to other algae. Some cyanobacteria utilize gaseous nitrogen mixed into the water from the atmosphere and only need phosphorus from the water to grow. Therefore, phosphorus released from anoxic bottoms particularly favours the formation of cyanobacterial blooms. Some cyanobacteria can also store nutrient phosphorus. Additionally, cyanobacteria have gas vesicles in their cells, allowing them to rise to the illuminated surface layer. Nitrogen fixation by cyanobacteria also provides nutrients for other algae.
Some cyanobacteria are toxic
In the Baltic Sea, large cyanobacterial blooms are mainly formed by two species: Aphanizomenon flos-aquae and Nodularia spumigena. The latter produces a liver toxin called nodularin.
Although not all cyanobacteria are toxic, confirming toxicity would always require more detailed tests. Therefore, all cyanobacterial blooms should be approached with caution, and it is not advisable to swim in water containing cyanobacteria. Cyanobacterial water should not be used for sauna steam, as the toxic vapours are dangerous to inhale.
The Poison Information Centre answers questions related to the prevention and treatment of acute poisonings around the clock at the toll-free number 0800 147 111.
Reporting cyanobacterial observations
Cyanobacteria appear in the water as green, blue-green, or yellowish particles. In calm weather, cyanobacterial masses washed ashore can form a dense “paint layer” on the surface. In early summer and spring, yellowish pollen can also be seen on the water’s surface, which can be easily mistaken for cyanobacteria.
It is advisable to report algal observations either through the vesi.fi map service or via the Havaintolähetti app. This way, you can warn others on the shore about cyanobacteria. It is also important to report “no algae” observations. Observations reported through both services will be visible on the vesi.fi service(siirryt toiseen palveluun) (in Finnish), Järvi-Meriwiki(siirryt toiseen palveluun) (in Finnish), and Itämeri.fi.
Vesi.fi service
Report your observation and check the cyanobacteria situation on the map.
