A new report showed dissolved oxygen levels have dropped by about 20 percent from their long-term average in the Gulf of Mexico in areas where federal and independent scientists previously reported the presence of subsurface oil. Scientists from agencies involved in the report attribute the lower dissolved oxygen levels to microbes using oxygen to consume the oil from the BP Deepwater Horizon oil spill. These dissolved oxygen levels, measured within 60 miles of the wellhead, have stabilized and are not low enough to become "dead zones."...