What caused dolphin deaths - oil spill or cold snap?, Reuters, March 4, 2011:
Marine scientists are debating whether 80-plus bottlenose dolphins found dead along the U.S. Gulf Coast since January were more likely to have perished from last year's massive oil spill or a winter cold snap. ...
Although none so far showed outward signs of oil contamination, suspicions immediately turned to petrochemicals that fouled Gulf waters after a BP drilling platform exploded in April 2010, rupturing a wellhead on the sea floor.
Dead dolphins continue to wash ashore in the Gulf, Houma Today, March 1, 2011:
Mandy Tumlin, sea turtle and marine mammal stranding coordinator with the [Louisiana] Department of Wildlife and Fisheries, said as of Tuesday, Louisiana had investigated 35 marine mammal standings this year. Unlike neighboring Gulf states, only four of those were baby dolphins.
That includes two whales, a pygmy sperm whale, which are not much larger than a dolphin and known to reside in the northern Gulf, and another whale that was too decomposed to identify. Two of the stranded dolphins were adults found alive. Four were visibly oiled, Tumlin said.