As rain deluged the Midwest this spring, commercial fisherman Ryan Bradley knew it was only a matter of time before the disaster reached him.

All that water falling on all that fertilizer-enriched farmland would soon wend its way through streams and rivers into Bradley’s fishing grounds in the Gulf of Mexico, off the Mississippi coast. The nutrient excess would cause tiny algae to burst into bloom, then die, sink and decompose on the ocean floor — a process that sucks all the oxygen from the water, turning it toxic. Fish would suffocate or flee, leaving Bradley and his fellow fishermen nothing to harvest.

Scientists from the National Oceanic and Atmospheric Administration and Louisiana State University confirmed Bradley’s worst fears in forecasts published Monday, predicting this spring’s record rainfall would produce one of the largest-ever “dead zones” in the Gulf of Mexico. An area the size of New Jersey could become almost entirely barren this summer, posing a threat to marine species — and the fishermen who depend on them.