Around the world, waters low in oxygen levels are becoming increasingly common, and climate change predictions suggest this is a situation likely to get worse. As oxygen levels drop, freshwater and marine life suffers, diversity plummets, and areas can become dead zones. But what if we could pump in more oxygen, and bring these underwater graveyards back to life?

A team working in Sweden have attempted just that. In a pilot project, scientists from Sweden and Denmark set up a pump system in the oxygen-deficient Byfjord, near Gothenburg. The system moved oxygen-rich water from the surface down to the depths of the fjord, where oxygen levels were very low and the only life was nitrate-breathing bacteria. Surface water pumped down was immediately and naturally replaced with healthy, oxygen-rich water flowing into the fjord from the Kattegat Ocean.

Months of pumping later, and higher levels of oxygen in the depths were recorded. “In the later phase of the experiment the entire water column began to look healthy,” said researchers Michael Forth and Alexander Treusch. “Many of the oxygen-needing bacterial species had returned and new bacterial communities similar to those in natural oxic fjords formed. This showed us that the idea worked.”

A tale of oxygen-breathing bacterial life returning to previously dead waters and a success for the team. Could these methods be used on a larger scale? Next, the scientists are turning their attention towards oxygen-poor areas of the Baltic Sea. “The bacterial communities in the Baltic Sea are very similar to those in Byfjord before the fjord was aerated. So it is fair to imagine that the same change in the bacterial community will take place in the Baltic Sea.” If the enterprising method continues to be a success, it will be invaluable in bringing life back to dying depths. 

 

Forth, M, Liljebladh, B, Stigebrandt, A. et al. (2015). Effects of ecological engineered oxygenation on the bacterial community structure in an anoxic fjord in western Sweden. The ISME Journal (2015) 9, 656-669; doi:10.1038/ismej.2014.172. 

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