Dolphin deaths - oil spill or cold snap?
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.
The National Oceanic and Atmospheric Administration declared "an unusual mortality event" last week when the number of dead dolphins washing up in Louisiana, Mississippi, Alabama and Florida had reached nearly 60, about half of them newly born or stillborn calves.
The death toll along 200 miles of shoreline has climbed to at least 82 since then, many times the normal mortality rate for dolphins along the Gulf Coast this time of year.
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.
Eleven workers were killed in the blast, and an estimated 5 million barrels (206 million gallons) of crude oil spewed into the Gulf over more than three months.
Scientists in the Gulf already were in the midst of investigating last year's discovery of nearly 90 dead dolphins, most of them adults, when officials became alarmed at a surge in dead baby dolphins turning up on beaches in January.
The latest spike in deaths, and a high concentration of premature infants among them, has led some experts to speculate that oil ingested or inhaled by dolphins at the time of the spill has taken a belated toll on the marine mammals, possibly leading to dolphin miscarriages.
The die-off has come at the start of the first dolphin calving season in the northern Gulf since the BP blowout.
But scientists at the independent Dauphin Island Sea Lab in Alabama suggested on Thursday that unusually chilly water temperatures in the Gulf may be a key factor.
Photo credit: http://www.imms.org/Article_2009_March_11.php