Satellite photos show cyanobacteria blooms in Lake Peipus
Recently, the Health Board of Estonia announced that large amount of blue-green algae has been found in the water of Lake Peipus. Satellite images indicate that east wind, which was blowing at the end of last week, had caused more intense blooms near the western shore of Lake Peipus by June 21. Blooming can also be seen on photos from June 23 (gallery below).
Blooms of water are considered to be situations where the increase of microorganisms makes the water cloudy and changes its colour. The blooms mostly occur in the summer due to blue-green algae or other algae. Blue-green algae, also called cyanobacteria, are different from other algae: they have similarities with bacteria, as the name suggests. Cyanobacteria can always be found in the water, but to start spreading massively, they need at least a week of warm, calm weather as well as nutrients – mainly nitrogen and phosphorus. They can acquire nitrogen from both water and air, but phosphorus only from water.
Comparison of the photos in the gallery below indicates that east wind, which was dominating at the end of last week, has caused more intensive blooming. This conclusion can be drawn by observing the greenish area near the western shore of the lake, indicating an increase of phytoplankton level in the water. However, it is important to note that the type of the blooming algae cannot be determined from satellite photos.
When there are high levels of cyanobacteria in the water, it is best not to swim in that area. Many blue-green algae that cause the blooms can produce toxic substances which are transfered into the water during decomposition. One of the organs these substances could harm is the liver, although no serious health problems are known to have been caused by blue-green algae in Estonia. Blue-green algae can only cause health problems when large amounts of the blooming water is swallowed. The toxic substances cannot absorb through skin, although for some people, they can cause skin irritation, burning sensation in the eyes, or a runny nose. Blue-green algae are dangerous for pets as well.
After the visible bloom, toxic substances can remain in the water up until four weeks. The disappearance of the substances depends on how fast and to which extent the water changes. The size of the waterbody is one of the factors that has an effect on how fast it takes for the water to be cleared of the substances.
Health Board of Estonia's guide to recognizing blue-green algae blooms
It is possibly blue-green algae, if
- it is late summer (July, August);
- the water has turned slightly yellow or green;
- the water and the shore are covered with a thick substance of green or blue-green color;
- the particles of the substance are so small that they do not stay on a wooden stick which is placed into the water;
- the water has a smell similar to mildew.