ORLANDO, Fla., July 19 (UPI) -- The 2011 BP oil spill and other environmental factors led to a historically high number of dolphin deaths in the Gulf of Mexico, a two-year study found.
Scientists have been trying for the past two years to understand the reason for a high number of dolphin deaths, part of what's called an "unusual mortality event," along the northern Gulf of Mexico.
Biologists were especially concerned with the exceptionally high number of young dolphins that made up close to half of the 186 dolphins that washed ashore from Louisiana to western Florida.
"Unfortunately it was a 'perfect storm' that led to the dolphin deaths," Graham Worthy, a University of Central Florida biologist, said.
"The oil spill and [previous] cold winter of 2010 had already put significant stress on their food resources, resulting in poor body condition and depressed immune response," he said in a university release Wednesday.
The cold winter of 2010 was followed by the historic BP Deepwater Horizon disaster in April 2011, which dumped millions of gallons of oil into the Gulf of Mexico, likely disrupting the food chain in the middle of the dolphins' breeding season.
Then a sudden entry of high volumes of cold freshwater from Mobile Bay in 2011 imposed additional stress on dolphins that were already in poor body condition.
"It appears the high volumes of cold freshwater coming from snowmelt water that pushed through Mobile Bay and Mississippi Sound in 2011 was the final blow," Worthy said.