Certain parts of Earth’s oceans are so oxygen depleted that they can hardly sustain life. Climate models predict that these “dead zones” will expand as global warming progresses, affecting ecosystems, fisheries, and the climate itself. Now Lengger et al. provide new evidence that such predictions do not adequately account for the activity of anaerobic microbes that consume inorganic carbon within dead zones.
Dead zones form where photosynthetic algae rapidly flourish in surface waters. As vast numbers of algae die and sink through the water column, aerobic microbes break them down, consuming nearly all available oxygen in the process. With so little oxygen left in deeper waters, microbes are unable to completely decompose much of the sinking organic matter before it settles on the seafloor.