Ecology
Dolphins are dying in large numbers in the Gulf of Mexico. Scientists can't name the exact reasons yet, but oil, bacteria, or some other unknown factors may be to blame.
On average, 74 dolphins are washed ashore on the northern coast of the Gulf of Mexico each year, especially in spring when new offspring are born. Between February 2010 and April 2012, the bodies of 714 dolphins and cetaceans were found on the coast of Louisiana and Texas, according to the National Oceanic and Atmospheric Administration. 95 percent of these animals were dead.
Since many of the dead dolphins go to the bottom, decompose at sea or are eaten by scavengers, the death rate among dolphins may be much higher. The death of animals coincides with the Deepwater Horizon disaster and the oil spill in April 2010. However, in fact, mortality began to rise two months before the disaster.
In the summer of 2011, 32 live dolphins were washed ashore in Barataria Bay, where the effects of the oil spill were particularly felt. They were underweight, lethargic, had low blood sugar levels, and had some symptoms of liver and lung disease. About half of them had low levels of hormones that help fight stress, support the immune system and metabolism. These symptoms have been seen in animals that are exposed to oil pollution.
It is still a mystery why dolphins began to die in large numbers even before the disaster. One of the causes could be the brucella bacterium. However, few of the dolphins found were infected with the bacterium. Scientists are continuing to search for the cause.