Global Warming

The Oceans are Suffocating

Ocean "dead zones" — regions of the sea where oxygen is severely or entirely depleted and most forms of life can't survive — are becoming more numerous, and scientists warn that they will continue to increase unless we curb the factors driving global climate change, which is fueling this alarming shift in ocean chemistry.

Even outside these , rising global temperatures and influxes of nutrient pollution are throttling oxygen levels in the open ocean and in coastal areas, threatening communities of sea life around the world.

While water molecules contain oxygen atoms, liquid water must also contain dissolved oxygen in order for fish and other organisms to breathe. Oxygen-deprived dead zones were first identified in estuaries — bodies of water where rivers flow into the sea — in the mid-19th century, and their oxygen depletion was linked to the presence of urban sewage in the water.

Since then, growth of industrial and agricultural activity has disrupted the ocean's chemical balance, with regions in many areas worldwide becoming infused with pollutants and nutrients that starved the water of oxygen. Meanwhile, rising global temperatures hamper oxygen's solubility in water and restrict its distribution into the deeper ocean. At the same time, some forms of marine life have grown increasingly stressed due to warmer and , which increases their oxygen requirements.

As oxygen levels in water drop, the behavior and growth of fish and other ocean organisms is affected — a lack of oxygen can make them more susceptible to disease, or make it more difficult to reproduce. In extreme cases, they can suffocate. Most larger forms of sea life either die or abandon oxygen-starved waters, invading nearby ecosystems where they may upset the balance of life, disrupt food webs or increase their vulnerability to predators.