Algae Whirlwind in Baltic Sea: Beauty and Danger

In 2018, satellite images captured a stunning spiral bloom of cyanobacteria in the Baltic Sea, creating a massive “dead zone” the size of Western Virginia by depleting oxygen in the water. This green spiral was a result of an extensive algae bloom, with the spiral covering about 25 kilometers in the Gulf of Finland – an area between Finland, Estonia, and Russia, as reported by NASA’s Earth Observatory. The whirlwind was primarily made up of tiny photosynthetic bacteria called cyanobacteria and diatom algae with a glass shell.

The large mass of microscopic organisms gathered in a whirlpool formed by the convergence of two opposing currents, creating an unusually perfect spiral rarely seen. While the visual spectacle can be mesmerizing, it poses a hidden danger by creating a toxic “dead zone” where oxygen levels in the water decrease, potentially suffocating marine life that rely on oxygen.

Algae blooms occur naturally in this part of the sea every summer when nutrients are brought to the surface due to vertical ocean mixing. However, human activities such as agricultural runoff have contributed to the increased size and frequency of these blooms over the years. A study in 2023 showed a 13% increase in the average size of algae blooms worldwide from 2003 to 2020.

The expansion of algae blooms also leads to larger “dead zones”, with the 2018 Dead Zone in the Gulf of Finland covering approximately 70,000 square kilometers, equivalent to the size of Western Virginia. Warmer sea surface temperatures, attributed to climate change, are lowering oxygen levels in the upper ocean layers, making it easier for oxygen levels to drop to dangerous levels.

Recent years have seen a rise in both the number and severity of “dead zones”, with the oxygen levels in the Baltic Sea reaching their lowest point in 1,500 years based on the 2018 study. With record sea surface temperatures recorded in the past year, further expansion of algae blooms worldwide is expected during the summer, partly due to the recent El Nino event.

/Reports, release notes, official announcements.