2012-04-03 "What’s Killing Thousands of Dolphins in the Gulf?" by Kristina Chew
Between February 2010 and April 1, 2012, 714 dolphins and other cetaceans — 95 percent of them dead — washed up on the northern shore of the Gulf of Mexico, from the border Louisiana and Texas share to Franklin County in Florida. The average number of dolphins who are stranded in a year is 74: What’s going on?
Now the National Oceanic and Atmospheric Administration (NOAA) is saying that those 714 animals found represent only a fraction of how many are actually perishing in what appears to be a massive die-off. Many of the dolphins sink, decompose or are eaten before they wash up to shore, notes Tim Wall at Discovery News [http://news.discovery.com/earth/hundred-of-dolphins-dying-mysteriously-in-gulf-120403.html]. The NOAA has now declared the die-off an “Unusual Mortality Event,” according to the Marine Mammal Protection Act of 1972.
The frightening die-off does coincide with BP’s Deepwater Horizon oil spill and its aftermath. A recent study has found that exposure to oil leads to serious health problems for dolphins.
Could a Bacteria Be The Reason So Many Dolphins Dying?
But as Wall at Discovery News points out, the increase in dolphin deaths started happening two months before the April 20, 2010 explosion that led to a months-long oil spill. 112 dolphins were found to have died before the spill and the NOAA says that the Brucella bacteria could be the culprit [http://www.nmfs.noaa.gov/pr/health/mmume/cetacean_gulfofmexico2010.htm].
The NOAA found Brucella in five stranded dolphins from Louisiana and its scientists have now been focusing on cases showing “pathological changes consistent with the fetal pneumonia or adult meningitis identified” in the original five cases. Infection with Brucella causes a disease, brucellosis, that, according to the NOAA, is “best known for its role in causing abortion in domestic livestock and undulant fever in people”; it can also cause infections im the brain, skin and bones. Scientists currently do not know how brucellosis is spread in dolphins. In domestic livestock, brucellosis spreads when animals consume the tissue and fluids left after delivery of a fetus and also via “inhalation, contact with a wound, and during nursing and breeding.”
However, dozens of the dolphins who have washed up show no sign of Brucella infection. NOAA scientists are continuing to investigate the possible role of the Deepwater Horizon oil spill in the Unusual Mortality Event, to figure out what is behind the shockingly high numbers of dolphins perishing in the Gulf of Mexico.