First, they considered the possibility that seasonal upwellings of toxic or oxygen-poor bottom water were responsible.

ECONOMIST: What killed Fossil Lake?

But it concludes that the oil is continuing to break up and disperse underneath the surface, making the emergency of a major oxygen-poor dead zone unlikely.

CNN: No signs of 'dead zone' in Gulf, feds say

The EPA pulled off the feat by sharply increasing the amount of oxygen-poor exhaust that is recirculated into the combustion chamber and increasing the pressure of the fuel being forced into the cylinder.

FORBES: EPA, Inc.