Algae blooms in the Baltic Sea causing oxygen levels to plummet

Phytoplankton spread across hundreds and even thousands of kilometers in the North Atlantic and Arctic Oceans every summer. According to NASA, blooms off the coast of Scandinavia are particularly intense this year.

The ancient organisms can be found in just about any body of water, but they thrive in the stagnant water of lakes and ponds. Phytoplankton are known to create unique toxins that can be fatal to animals, but the human health impacts of these toxins are not fully understood.

The largest outbreaks in reservoirs and lakes have made hundreds of people sick, and officials in some regions restrict recreational activities during phytoplankton blooms. A heatwave triggered a massive algae bloom in the Baltic last week that shut down beaches along the coast.

In humans, high doses of the toxins can cause liver damage and attack the nervous system. It is still relatively unknown how exposure to low levels of the toxins may affect human health, but small studies have found that even small doses of some of the toxins may be linked to liver cancer or neurodegenerative disease.

The prevalence of algae blooms in the Baltic Sea in recent years has caused more frequent “dead zones,” or oxygen-deprived regions, across the basin.

The phytoplankton, which are also known as cyanobacteria, are driven primarily by fertilizer and sewage runoff.  They reproduce quickly, consuming the abundant nutrients in the Baltic and depleting the water of oxygen.

A study published earlier this month in the journal Biogeosciences referred to the algae blooms in the Baltic as being “unprecedentedly severe.”

The researchers pointed out that the Baltic has a limited ability to flush out pollutants, which makes it exceptionally vulnerable to these events. As a result, oxygen in the Baltic Sea has recently reached its lowest levels in nearly 1,500 years.

According to researchers from the University of Turku, one particular dead zone is estimated to span about 27,000 square miles this year.

On July 18, 2018, the Operational Land Imager (OLI) on NASA’s Landsat 8 captured the image of a green phytoplankton bloom in the Gulf of Finland with a striking swirling pattern. The giant bloom, which is over 15 miles across, appears to be projected from the circular motion of an ocean eddy that is pumping nutrients up from the water’s cold depths to the surface.

The Baltic Sea is surrounded by nine countries and has an estimated 16 million people living along its coastline.
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By Chrissy Sexton, Earth.com Staff Writer

Image Credit: NASA Earth Observatory