National Centers for Coastal Ocean Science supported scientists have documented that the 2011 "dead zone"(area of hypoxia, or low oxygen) in the northern Gulf of Mexico west of the Mississippi River delta now covers at least 6,765 square miles of sea floor. This dead zone area is nearly equal to the 5-year average, but well above the long-term average.

The scientists had predicted a record sized dead zone following record-breaking flow of the Mississippi River this spring and summer, but winds and waves from Tropical Storm Don disrupted the western portion of the dead zone. Wind and wave mixing of the water column re-supplies oxygen to the lower layers and reduces the area of low oxygen.

The dead zone was measured by scientists from the Louisiana Universities Marine Consortium (LUMCON) and Louisiana State University aboard the RV Pelican. NCCOS has supported the mapping of the dead zone in the northern Gulf of Mexico since 1990.