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.