Dead Zones Multiply Worldwide

The journal Science published a report from Professor Robert Diaz of the Virginia Institute of Marine Science showing that the number of "dead zones" in coastal waters worldwide has increased by a third between 1995 and 2007. When scientists first described these areas of low oxygen or hypoxic waters in 1910 there were only four. Now there are 405 covering an area of 95,000 square miles. Perhaps the most well known is the one in the Gulf of Mexico at the mouth of the Mississippi. It is the size of New Jersey. The largest is the Baltic Sea which entirely hypoxic year round. The main channel of Chesapeake Bay hypoxic in summertime. Only bacteria feeding on decomposing algae blooms in turn created by excess nutrients like nitrogen and phosphorous can live in the zones. The nutrients causing the condition are primarily run-off from agricultural lands impregnated with chemical fertilizers. Dead zones kill and stress fish and other food species. Stripped bass in the Chesapeake suffer from bacterial infections due to the seasonal hypoxia which forces them to live in warmer surface waters away from the dead zone in the cooler bottom waters they prefer. Scientists estimate that the Bay looses about 5% of its food energy every year to hypoxic conditions.