Bacteria, cold water, and probably oil killed baby dolphins in Gulf, say scientists (+video)
A new report indicates that snowmelt entering the Gulf of Mexico is the culprit for the mass infant dolphin stranding in early 2011.
Surges of snowmelt pouring into the Gulf of Mexico may have been a final stress affecting when and where 86 baby dolphins were aborted or died shortly after birth in early 2011, researchers say.Skip to next paragraph
In Pictures Pink dolphins
Subscribe Today to the Monitor
Water temperatures fell in Mobile Bay and Mississippi Sound two to three weeks before each peak in infant dolphin strandings, a new research paper reports.
The cold water may have been the final straw for animals already prone to premature birth for other reasons and probably stressed both by the 2010 oil spill and the unusually cold winters that bracketed it, said Ruth H. Carmichael, senior marine scientist at Alabama's Dauphin Island Sea Lab.
"These freight trains of cold fresh water may have assaulted them, essentially kicking them when they were already down," she said.
It's too early to comment on causes or contributing causes, especially since dolphins are still dying at higher rates than normal, said Teri Rowles, a National Oceanic and Atmospheric Adminstration scientist. She has been studying the deaths of at least 753 dolphins since February 2010 in the northern Gulf of Mexico, where the BP well began spewing oil on April 20, 2010.
"We typically don't come out with a conclusion about contributing factors and causing until it's over and we can sit down and look at all the data and all the analyses together," she said Wednesday.
The one common thread so far has been brucellosis, found in 12 of 51 animals tested so far for Brucella bacteria, she said. At least three of the dolphins which tested positive for the bacteria were adults or subadults, but most were infected while still in the womb.
"They were infected in utero and they died before they took a breath," she said.
Rowles said samples are still being tested to learn whether they are all the same strain or different strains of Brucella.
The deaths started during prolonged cold, when other coastal species also were dying. Though the totals for this past May and June are far below those for the same months in 2010 or 2011, they are still above normal, according to NOAA.
"We're focused on a small portion of that big event," Carmichael said.