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The National Oceanic and Atmospheric Administration is predicting this year's annual "dead zone" in the Gulf of Mexico to be unusually large, coming in at "approximately 7,829 square miles, or roughly the size of Massachusetts."
Context: A dead zone is a hypoxic area, meaning that little or no oxygen is present, killing most marine life. NOAA says the event is largely a result of nutrient pollution flowing into the Gulf from the Mississippi River watershed. The surplus of nutrients, such as phosphorous, results in excess algae growth. When decomposed in water, the algae causes oxygen levels to plummet in the ocean's depths.
NOAA's prediction states that a major cause of this summer's near-record size is the torrential rainfall over the central part of the U.S., which flooded farmer's fields and caused record river flooding and nutrient dumping.
What it means: The dead zone could cause a tremendous loss of marine wildlife along the Gulf Coast. Last summer, a severe red tide similarly damaged a smaller section of the Gulf, with a surplus of algae suffocating marine life and leaving beaches riddled with fish carcasses.