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.

The article goes on to blame high-nutrient runoff, mainly poisoned by the fertilizers that have been rinsed off industrial-sized farms.

When these nutrients, heavy in nitrogen, enter the water, microscopic plants and animals (algae and dinoflagellates) have more food than they know what to do with, so they reproduce in massive numbers known as “blooms.” These blooms are so enormous they can be seen from far away, and are capable of choking marine mammals and fish and literally blocking out the light on the bottom of the ocean.

The dark spots kill off all the native plant life and force animals to leave. The huge blooms of these organisms also suck all the oxygen out of the water with their rapid growth and that can kill any fish or other animals like crabs and shrimp in the area.

You can just imagine what happens when all that junk dies.

“The overwhelming response of the organisms in our coastal areas is to migrate or to die,” Dr. Diaz said. “To adapt to low oxygen water, it has to be a part of your evolutionary history — it’s not something you can develop in a 40- or 50-year time period.”

The marine life lost each year to the dead zone in the Gulf of Mexico, he said, would supply about 75 percent of the brown shrimp catch with food for a year. In the Baltic Sea, dead zones lead to the loss of about 1.3 million metric tons of fish food each year.

“Once they recur, they are very hard to reverse,” said Donald F. Boesch, president of the University of Maryland Center for Environmental Science. “They have major consequences for the ability of fish populations to renew themselves.”

One of the most famous examples, in the Gulf of Mexico, covers an area the size of Massachussettes! Even more frighteningly, “Scientists estimate that cutting the Gulf of Mexico’s dead zone by a third would require a 45 percent decrease in nitrogen-rich runoff from the Mississippi River watershed, which extends into the croplands of the upper midwest.”

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Source: NYTimes

Technorati Tags: ocean, marine conservation, dead zones, fertilizer, environment, pollution

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