Scientists
are expecting what they call an average sized "dead zone" in the Gulf
of Mexico this year.
Scientists
are predicting the area will measure about 5400 square miles – A little less
than the 5-year average, but much smaller than the 8800 square-mile 2017 Gulf
hypoxic zone, which was the largest zone measured since mapping began in 1985.
The
Gulf dead zone forms each spring and summer off the Louisiana and Texas coast
when oxygen levels drop too low to support most life in bottom and near-bottom
waters.
The
zone is caused by nitrates and nitrogen from fertilizer and urban runoff
flowing down the Mississippi River.
When
the excess nutrients reach the Gulf, they stimulate an overgrowth of
algae, which eventually die and decompose, depleting oxygen as they sink to the
bottom.
The
resulting low oxygen levels near the bottom of the Gulf cannot support most
marine life.
Fish,
shrimp and crabs often swim out of the area, but animals that are unable to
swim or move away can be stressed or killed.
The
amount of nitrogen entering the Gulf of Mexico each spring has increased by
about 300 percent since the 1960s, mainly due to increased agricultural runoff.
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