In the USA, crop fertilizers that wash into the Mississippi river cause a large dead zone in the Gulf of Mexico. Corn requires much fertilizer, so the increased corn ethanol crops contribute to the dead zone.
Ocean 'dead zones' on the rise
By Bina Venkataraman
Coastal oceans are being starved of oxygen at an alarming rate, researchers are reporting, with vast stretches of water along the seafloor depleted of oxygen to the point that they can barely sustain marine life.
The main culprit, scientists say, is nitrogen-rich nutrients from crop fertilizers that spill into coastal waters by way of rivers and streams.
In a study to be published Friday in the journal Science, researchers say the number of marine "dead zones" around the world has doubled about every 10 years since the 1960s. At the same time, the zones along many coastlines have been growing in size and intensity. About 400 coastal areas now have periodically or permanently oxygen-starved bottom waters. Combined, they constitute an area larger than the state of Oregon.
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