During summer months, algae blooms covering large areas of the Baltic Sea are a common phenomenon. High nutrition inflow from the adjacent land, a low exchange of fresh water with the open Atlantic Ocean and plenty of sunlight all together create perfect conditions for algal growth. 2015 was not an exception as a large bloom was underway south of the Finnish skerry coast in the Gulf of Finland during August. Clear skies allowed Landsat 8 to get an impressive view on August 11th:
The image covers about 65*40 km of the most structured part of the bloom. The left image above shows EOMAP’s Sum of Organic Absorption (SOA) product which is the absorption of light [1/m] by particulate and dissolved organic matter. The highest values of organic absorption (light blue) can therefore be found along the densest algal patches which can also clearly be seen in the underlying true color RGB image (LS8 channels 4-3-2). You can use the slider to switch between the both images.
Another comparison reveals further characteristics of the most recent bloom:
On the right side, EOMAP’s chlorophyll-a product provides an absolute measure of the chlorophyll-a concentration in [µg/l]. Moreover, the company’s recently launched harmful algae bloom (HAB) indicator algorithm (for further reading please read here) indicates the presence of cyanobacteria containing phycocyanin. Indeed, the algal bloom contains cyanobacteria of type Nodularia1 which are a common for algal blooms in the Baltic Sea2.