Climate Change Could be Keeping the Baltic Sea Starved for Oxygen

The Baltic Sea is certainly not the only part of the world still suffering from when humanity didn't understand the consequences of its actions. However, compared to other parts of the world, it may be one of the most stark examples of how climate change can just perpetuate these problems.

That's because the Baltic Sea is home to the Boknis Eck time series station. Based just off the coast of Schleswig-Holstein at the exit of Eckernförde Bay, this station has been recording environmental parameters concerning the Baltic Sea since 1957, painting a particularly detailed picture of how human and natural factors have been changing the sea around it.

"It is one of the oldest active time series stations for this kind of data worldwide," Hermann Bange, a scientific coordinator at the GEOMAR Helmholtz Centre for Ocean Research Kiel, said in a recent statement.

The data from this station also follows how the Baltic Sea slowly began to lose oxygen (hypoxia) near its sea floor thanks to the large-scale dumping of agricultural fertilizers and sewage into the sea.

"That meant an oversupply of nutrients. Algae were then able to proliferate, and as soon as they die and sink to the bottom, microorganisms decompose the biomass and consume a lot of oxygen; this resulted in large oxygen-free zones at the bottom of the Baltic Sea to be formed " explained Sinikka Lennartz.

Lennartz, Bange, and a number of their colleague recently authored a study closely examining how, even after the Baltic countries took actions to improve the protection of the sea in the 1980s, the hypoxia persists.

"The oxygen trend is still down significantly," Lennartz explained. "We see more and more events at Boknis Eck when no oxygen is measured below 20 meters depth."

So what's going on? the researcher suggest climate change is to blame, where warming waters and changing trade winds are mitigating efforts to help the Baltic Sea recover.

"In late summers the temperature on the seafloor has risen by an average of 0.4 degrees per decade. Higher temperatures also mean a more efficient degradation of biomass and therefore more consumption of oxygen," Bnage explained. "Nevertheless, the bordering countries should not subside in their efforts to protect the environment. With increasing temperatures, the Baltic Sea would become eutrophic a lot faster if we reintroduced more waste."

These results and more were recently published in the journal  Biogeoscience.

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