The National Oceanic and Atmospheric Administration estimates the algae-choked “dead zone” in the Gulf of Mexico near the mouth of the Mississippi River spanned 7,829 square miles this summer, roughly the size of Massachusetts and considerably above the 6,000-square-mile five-year average. The largest recorded Gulf dead zone to date was 8,776 square miles in 2017. Dead zones occur when algae sinks and decomposes, sucking oxygen from the water and making it impossible for marine life to exist, jeopardizing billions of dollars generated by commercial fishing in the area. The phenomenon is primarily attributed to chemical fertilizer runoff from Midwestern farms into the Mississippi, exacerbated by warming trends.