"In June, scientists predicted that the Gulf of Mexico’s annual dead zone — a subsea region where the water contains too little oxygen to support life — might develop into the biggest ever. In fact, that didn’t happen. Owing to the fortuitous arrival of stormy weather, this year’s dead zone peaked at about 6,800 square miles, scientists reported on Aug. 1 — big but far from the record behemoth of 9,500 square miles that had been mentioned as distinctly possible.
That’s the good news. The bad: Substantial portions of the affected Gulf weren’t just low in oxygen, but virtually devoid of it from the surface to the seafloor. And researchers could literally smell the problem, notes Nancy Rabalais, executive director of the Louisiana Universities Marine Consortium, based in Chauvin. Where oxygen loss occurs at the seafloor, she reports, the sediment gurgles up hydrogen sulfide — a gas that carries the stench of rotten eggs to the surface."
Janet Raloff reports for Science News August 2, 2011.