Whales may be able to get the same decompression sickness that scuba divers do when they surface too quickly from a dive, despite their adaptations to a life in the ocean.
The painful and potentially life-threatening condition known as decompression sickness, or the bends, occurs when gasses bubble out of solution in the body, forming air pockets in divers’ blood and organs as they rise. But scientists have had trouble studying this phenomenon in non-human divers because little is known about what happens to these gasses in non-human tissues.
Researchers from the University of North Carolina Wilmington investigated how marine mammals’ tissues—specifically, fat deposits in the jaws of toothed whales that are used in echolocation—absorb nitrogen gas, one of the gases that contributes to the bends. They found that the makeup of the fat affected how much nitrogen gas dissolves in it—and that different species had different fat compositions.
In combination with data on how often and how deep these marine mammals dive, the researchers could estimate whale species' risk for decompression sickness. They published their results Wednesday in the Journal of Experimental Biology.
Why It Matters
Once, scientists thought that diving sea creatures like the elusive, deep-diving Cuvier’s beaked whale were resistant to the bends, but mounting evidence suggests that this may not be entirely true.
In 2002, international navy sonar exercises were linked to a mass stranding of 14 whales in the Canary islands. The whales had gas bubbles in their tissues, a sign of decompression sickness.
“If, for example, sonar is affecting these animals so they get decompression sickness, what can we do to prevent that?” says Andreas Fahlman, a biology professor at Texas A&M University at Galveston who studies the physiology of deep diving animals. Fahlman was not involved in this research.
The Big Picture
To figure out how a sonar blast that startles a whale out of its normal diving behavior might pose a threat to its health, scientists need data on how much nitrogen gas whale tissues can absorb.
But that didn't exist until now; researchers were using data collected in olive oil and bone marrow from oxen and sheep—not marine mammals.
That’s why Gina Lonati, a graduate student at the University of North Carolina Wilmington, began collecting the heads of whales and other marine mammals, and extracting their fat.
“In order to see if these animals may be susceptible to something like the bends or decompression sickness, we want to see how much nitrogen their fats can hold,” she says. “Because the more they can hold, it’s possible the more it may affect them when they surface.”
Lonati says that her successor on this project is looking into the potential for gas exchange in the vasculature of an even bigger range of species. She hopes that her research will be used to revise the existing models of how diving marine mammals manage nitrogen gas when they dive.
Fahlman thinks that Lonati's results could also allow modelers to estimate how boats, or even climate change, might affect marine creatures like whales.
“It may seem like a very simple and detailed thing they’ve done, but the work that these people put into this, the difficulty to get these measurements—its absolutely phenomenal, he says. “Little by little we start to understand these animals more.”