Nearly all ocean dead zones will increase by the end of the century because of climate change, according to a new Smithsonian-led study. But the work also recommends how to limit risks to coastal communities of fish, crabs and other species no matter how much the water warms.
Dead zones are regions where the water has unusually low dissolved oxygen content, and aquatic animals that wander in quickly die. These regions can form naturally, but human activities can spark their formation or make them worse. For instance, dead zones often occur when runoff from farms and cities drains into an ocean or lake and loads up the water with excess nutrients such as nitrogen and phosphorus. Those nutrients feed a bloom of algae, and when those organisms die, they sink through the water column and decompose. The decomposition sucks up oxygen from the water, leaving little available for fish or other marine life.