Ocean Dead Zones Could Cause Mass Extinction

The number of oceanic dead zones in the world is increasing. In the zones oxygen levels are too low to sustain life. It is widely know that a monster area in the south Atlantic is growing in size, but there are hundreds more smaller dead zones. They are caused by overfishing and the nutrient rich residue in fertilizer runoff.

Climate change also plays a part. As oceans warm up layers form and some become stagnant with low oxygen levels. Long standing currents and wind directions have changed which has reduced layer intermixing.

Since 2000 over 400 dead zones have been identified. In the 1980s there were little more than a hundred. Some are huge, more than 70,00 sq kilometers, while many are less than a square kilometer.

The lack of oxygen not only causes death. Offspring are born deformed. They do not survive, or produce fewer young. Danger of a mass extinction is now very high. Dead zones are forming on continental shelves where most fishing is done. The mere presence of humans is deemed to be a contributing factor to dead zones. Man changes the balance of life.
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