Dead Zones Return

It is that time of year again. Dead zones formed between the spring and summer in both the Chesapeake Bay and the Gulf of Mexico. Scientists began studying this phenomenon in the 1970’s and are still trying to control it.

According to NOAA, hypoxic zones are areas in the ocean of such low oxygen concentration that animal life suffocates and dies, and as a result are sometimes called dead zones. The marine life that is mobile and does not die, leave the area and it becomes a biological desert.

Hypoxia is a natural phenomenon that occurs periodically in both fresh and saltwater systems around the world. But what concerns scientists are dead zones created or enhanced by human activity such as those in the Chesapeake Bay and the Gulf of Mexico. There are many factors (physical, chemical and biological) that combine to create dead zones, but its primary cause by humans is nutrient pollution. Nutrients can run off of land from fertilizers used on agricultural fields or in urban areas where lawn fertilizers are used. Pet and wildlife wastes are also sources of nutrients as well as piped wastewater into rivers and coasts that can stimulate an overgrowth of algae which sinks and decomposes in the water.

Earlier this summer scientists were proclaiming that the dead zone in the Chesapeake Bay was the least amount they’d had since starting to monitor it 30 years ago. Unfortunately, there was a resurgence helped by some record setting rain that carried nutrient pollutions like nitrogen and phosphorus off the streets as well as millions of gallons of raw sewage that overloaded storm drains. In the end it was the eighth worst on record.

The Gulf of Mexico dead zone this year is the size of Connecticut. NOAA announced that an annual scientific survey found an area of 5,052 square miles of hypoxia, off much of Louisiana’s coast and part of Texas. While this is slightly smaller than what has been found in earlier years, it likely means that the target goal set by scientists to reduce the zone to 1,900 square miles by 2015 will not be met. The dead zone is formed largely by agriculture fertilizer and wastewater coming down the Mississippi River.

There are over 550 dead zones throughout the world. The largest is in the Baltic Sea and the dead zone in the Gulf of Mexico is the second largest caused by humans. Dead zones have a negative impact on our economy especially for our fishing industry. Estimates by NOAA found that algae blooms in the U.S. effected seafood and tourism to the tune of at least $82 million annually.

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