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Poison Zones
Unfortunately, the old idea that the deep sea is lifeless has led to a long history of dumping some of the most toxic waste into the seas. Though now illegal, not long ago everything from sewage sludge to drums of radioactive waste were dumped into the deep sea. Hydrocarbons from ocean drilling operations are still a source of deep-sea pollution.
According to the United Nations Environment Program (UNEP), dumping accounts for about 10 percent of all pollution to the deep sea. The top source of pollution is runoff from land (44 percent), followed by air pollution (33 percent) and losses from shipping (12 percent). Offshore oil and gas exploration and production adds about 1 percent more of toxic chemicals — usually concentrated in areas like the Gulf of Mexico and the North Sea, where they cause a far greater proportion of the deep-sea pollution.
Global Storehouse
The deep sea also plays another role often overlooked in the operation of Earth: storing heat. Seawater that is warmed at the surface eventually becomes dense with salts and sinks into the deep sea. There it retains heat that can take centuries to come again to the surface. This is a critical concern regarding global warming, since the only way to truly cool down Earth is to expel the heat trapped by the greenhouse effect into space. That's harder to do when the heat is trapped in the deep sea and taking its time coming up again.
Finally, there's the matter of carbon dioxide, the most notorious greenhouse gas. Microscopic ocean plants account for about half of all the carbon dioxide-absorbing photosynthesis on the planet. A lot of the carbon trapped by sea life near the surface eventually drops to the seafloor and is buried there — sequestered away from the atmosphere and out of the global warming equation for a long time. Without this giant carbon dioxide sink, the gas would increase faster in the atmosphere and global warming would accelerate even more quickly than it already is.
So no matter how otherworldly the deep sea may seem, it is actually an essential part of life everywhere on planet Earth.
