What does the blue-green algae look like on satellite observations at lakes, coast and the sea?

Blue-green algae, or cyanobacteria, is typically present from July to August on the lakes and Finnish Seas. Also, blue-green algae starts to form during warm early summers in June. In the early summer there can appear raft-like formations of pollen on the surface waters. Pollen and cyanobacteria are visually similar to each other but they can be separated from each other from satellite observations based upon the date and color-schema. In satellite observations blue-green algae typically contains different shades of green, meanwhile pollen looks lighter, yellowish or even white.

Examples how blue-green algae looks on lakes

Figure 1: The Lake Pyhäjärvi in Säkylä often has algae in July and August which is shown as green rafts and spirals (left image, Sentinel-2 1.8.2020) Observation in the Tarkka. In the spring and early summer light spirals and rafts of pollen can be spotted in the Lake Pyhäjärvi (right image, Sentinel-2 6.6.2021) Observation in the Tarkka. Located at the top of the left image the blue-green algae in Lake Köyliönjärvi appears as a green, flat cover.

In the Lake Evijärvi blue-green algae was observed in a Sentinel-2 image at 8 of August 2020 as green, wide, and flat areas. Observation in the Tarkka

Figure 2: The Lake Enäjärvi in Vihti is an eutrophic lake. The color of the Lake Enäjärvi changes during the summer. Observation in the Tarkka 7.5.2020, 21.6.2020 and 8.8.2020.

Examples, how blue-green algae appears in the coastal waters

Figure 3: In the topmost image at Upinniemenselkä there appear larged blue-green algae rafts at 17th of July 2018 Observation in the Tarkka. For comparison, the bottom image presents spring time pollen on top of the water from coniferous trees. Observation in the Tarkka. Pollen can be seen as light rafts and spirals meanwhile gren-blue algae can be seen as green formations.

Examples what blue-green algae looks like on the sea

In the Gulf of Finland blue-green algae was seen in the “algae summer of 2018” as large, green rafts and spirals. Observation in the Tarkka

In the Bothian Sea there are often large blue-green algae rafts. In the summer of 2020 the blue-green algae raft was given a nickname of Kraken by the press. Observation in the Tarkka