A team of Danish and Swedish scientists reports that they have restored oxygen to the watersof a deep fjord that had suffered from a long-term lack of oxygen. The researchers used large pumps to mix oxygen-rich surface water into the deeper parts of the fjord’s water column — which had long been anoxic due to its depth and geological setting — and after only two months higher oxygen concentrations became detectable in the bottom waters. “In the later phase of the experiment the entire water column began to look healthy,” the researchers said, noting that bacterial species that live in well-oxygenated waters had begun to appear. Low oxygen levels make waters uninhabitable to most forms of life, and anoxic waters often harbor only a few types of bacteria, some of which produce significant levels of greenhouse gases.