The National Oceanic and Atmospheric Administration just released a report that contains even more bad news for the Gulf of Mexico. This year’s Gulf Dead Zone will be unusually large — and that’s without accounting for any impact from the ongoing oil spill.

The Dead Zone refers to an annual oxygen-depleting algae bloom in the waters off the Gulf Coast. Krista Hozyash recently described its origin and impact in detail for Grist’s series on nitrogen, and Grist’s Tom Philpott summarized its cause in a post from the early days of the spill:

 Every year, millions of tons of synthetic nitrogen and mined phosphorous leach from Midwestern farm fields and into streams that drain into the Mississippi. The great river deposits those agrichemicals right into the Gulf, where they feed a 7,000-square-mile algae bloom that sucks up oxygen and snuffs out sea life underneath. The bulk of this vast Dead Zone’s rogue nutrients comes from the growing of corn, our nation’s largest farm crop.

According to NOAA, the average size of the dead zone over the last five years has been about 6,000 square miles. Current models predict something between 6,500 and 7,800 square miles which, as the report observes, is “an area roughly the size of Lake Ontario.”