BP Oil Spill Gives Insights into Marine Mammals Stress

Scientists have suggested three factors behind the increase in dolphin mortality rate in the Gulf of Mexico.

A team of biologists from various institutions in the Gulf of Mexico and the University of Central Florida revealed that the Deepwater Horizon oil spill followed by the cold winter in 2010 and release of cold water in 2011 were the main reasons behind the increase in the number of dolphin deaths.

Nearly 186 young bottlenose dolphins washed ashore from Louisiana to western Florida between January through April 2011. Eighty-six of those dolphins were near-birth or newborns that were stranded during the four-month period. The number of dolphins stranded was six times more than the number of dolphins that were stranded in the region since 2003, according to the researchers' study.

The BP oil spill caused massive destruction to the marine mammals in the Gulf of Mexico in 2010. Millions of gallons of oil leaked in the Gulf affecting the food chain of these underwater creatures, followed by cold winter hitting the area during the dolphin breeding season.

Besides the oil spill and cold winter, the cold water released from the Mobile Bay, an inlet in the Gulf of Mexico, in 2011 due to melting of snow caused a cold shock to the dolphins. The release of cold water put more stress on the perinatal dolphins, who are already in poor condition and facing stress due to reduction in the availability of food resources. Researchers noted the cold water flow and newborn dolphins washing ashore happened near the same place and during the same period.

"The oil spill and cold winter of 2010 had already put significant stress on their food resources, resulting in poor body condition and depressed immune response," said Graham Worthy, a UCF provosts distinguished professor of biology and co-author of the study, in a news release from the university. "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."

Scientists believe that the study will help further in understanding how the marine mammals respond to stress caused by such events. The study is published in the PLoS ONE journal.