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How Do Marine Mammals Avoid the Bends?

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Study offers new hypothesis and highlights role that sonar plays in strandings

Deep-diving whales and other marine mammals can get the bends—the same painful and potentially life-threatening decompression sickness that strikes scuba divers who surface too quickly. A new study offers a hypothesis of how marine mammals generally avoid getting the bends and how they can succumb under stressful conditions.

The key is the unusual lung architecture of whales, dolphins and porpoises (and possibly other breath-holding diving vertebrates), which creates two different pulmonary regions under deep-sea pressure, say researchers at the Woods Hole Oceanographic Institution (WHOI) and the Fundacion Oceanografic in Spain. Their study was published April 25, 2018, in the journal Proceedings of the Royal Society B.

Photo by Lance Wills, © Woods Hole Oceanographic Institution

How some marine mammals and turtles can repeatedly dive as deep and as long as they do has perplexed scientists for a very long time,” says Michael Moore, director of the Marine Mammal Center at WHOI and co-author of the study. “This paper opens a window through which we can take a new perspective on the question.

When air-breathing mammals dive to high-pressure depths, their lungs compress. That collapses their alveoli—the tiny sacs at the end of the airways where gas exchange occurs. Nitrogen bubbles build up in the animals’ bloodstream and tissue. If they ascend slowly, the nitrogen can return to the lungs and be exhaled. But if they ascend too fast, the nitrogen bubbles don’t have time to diffuse back into the lungs. Under less pressure at shallower depths, the nitrogen bubbles expand in the bloodstream and tissue, causing pain and damage.

Marine mammals’ chest structure allows their lungs to compress. Scientists have assumed that this passive compression was marine mammals’ main adaptation to avoid taking up excessive nitrogen at depth and getting the bends.

In their study, the researchers took CT images of a deceased dolphin, seal, and a domestic pig pressurized in a hyperbaric chamber. The team was able to see how the marine mammals’ lung architecture creates two pulmonary regions: one air-filled and the other collapsed. The researchers believe that blood flows mainly through the collapsed region of the lungs. That causes what is called a ventilation-perfusion mismatch, which allows some oxygen and carbon dioxide to be absorbed by the animal’s bloodstream, while minimizing or preventing the exchange of nitrogen. This is possible because each gas has a different solubility in the blood. The terrestrial pig did not show that structural adaptation.

This mechanism would protect cetaceans from taking up excessive amounts of nitrogen and thus minimize risk of the bends, says lead author Daniel García-Parraga of the Fundacion Oceanografic. However, he said, “Excessive stress, as may occur during exposure to human-made sound, may cause the system to fail and increase blood to flow to the air-filled regions. This would enhance gas exchange, and nitrogen would increase in the blood and tissues as the pressure decreases during ascent.

Scientists once thought that diving marine mammals were immune from decompression sickness, but a 2002 stranding event linked to navy sonar exercises revealed that 14 whales that died after beaching off the Canary Islands had gas bubbles in their tissues—a sign of the bends. The researchers say the paper’s findings could support previous implications of decompression sickness in some cetacean mass strandings associated with navy sonar exercises.

The team says further research will require the development of tools to analyze how lung blood flow and ventilation patterns change with various stressors during diving.

This work was supported by funding from the Fundacion Oceanografic and the Office of Naval Research.


The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean’s role in the changing global environment.

For more information, please visit www.whoi.edu.

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Scubaverse UWP Winners Gallery: Christian Horras

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Each month we give the winner of the Scubaverse Underwater Photography competition the opportunity to show off a little more of their work in a gallery. The March winner was Christian Horras and you can see their winning image at the top of this page.


What do you love about diving & underwater photography?

For me it is all about showing the beauty of our world underwater to people that don’t dive and thus can’t see it for themselves. I want to share my own passion for the amazing ecosystem that is so much older than everything we know living on land. As I am from Germany, there are only a few people in my surroundings that have ever seen a coral reef or a shark with their own eyes. It is a big privilege to be able to go diving all over the world and in return it should be our task to arise awareness of this fragile and endangered ecosystem.

What equipment do you use?

I use a Nikon D810 in a Isotta Housing and various lenses, depending on the subject: a Sigma 15mm F2.8 Fisheye, a Nikon 16-35 mm F4 and two Nikon Macro lenses (60mm and 105mm), as well as a WeeFine +13 Diopter. The Fisheye is my main lens, as it allows me to get really close and still cover a big field of view. For lighting I use two Retra Pro Strobes and a Retra Snoot.

Where can our readers see more of your work?

Website: www.christianhorras.com
Instagram: www.instagram.com/christian.horras/


To enter the latest Scubaverse Underwater Photography competition, with a chance to win some great prizes as well as have your own gallery published, head over to the competition page and upload up to 3 images.

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Emperor Divers reaches halfway in Covid Diver Heroes Initiative with fourth award

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Emperor Divers have reached the halfway point with their #coviddiverheroes initiative and are still receiving worthy nominations every day! Here, they recognise their 4th winner, another awesome hero from the diving community with an inspirational story of selflessness through the pandemic. Nominated by David White, Phuong Cao wins a free liveaboard trip in the Maldives when she can finally take some time off, and here is her story:

I, David White, would like to nominate Phuong Cao (36) for her tireless efforts fighting this pandemic. Not satisfied with being a frontline hospitalist in New York she took a second job on the COVID team in Guam to treat patients under even tougher conditions on her weeks off! She continues to commute 7750 miles each way and apply herself to both jobs for three months already and counting. Her energy level has no limits and she’s only happy when those in her care are on the mend. I think she definitely deserves a break! I guess the Maldives would be the best choice for her as I know she has dived with you in the Red Sea already.

Phuong Cao

We have been in touch with Phuong who had this to say: “Wow what a surprise! Thank you for the recognition. Holding my breath until I get back underwater!”

The halfway point is a good chance to remind people that the initiative is still running and the Emperor Divers team would love to hear about more heroes, as there are four more to award in the next 2 months!

Do you know a diver who has been heroic this past year? Emperor know that, worldwide, people have had to step up during this pandemic which has affected so many lives. They want to reward some real heroes with free liveaboard trips in the Red Sea or Maldives.

Luke Atkinson, Emperor’s Red Sea Manager, said: “This initiative is our way of saying ‘thank you’ to all those hundreds of people who have taken a selfless interest in looking after the vulnerable in their community. Examples could include healthworkers, carers or those who have come out of retirement to volunteer locally, but really we know there are many other ways people have been heroic.“

Emperor want to hear from people who know a heroic diver who would love to have a free liveaboard trip to look forward to in the future. People need to nominate a Covid Hero Diver and tell Emperor (in 100 – 200 words) why they deserve a free trip, and whether they would prefer the Red Sea or the Maldives. A multinational panel of Emperor’s most loyal and compassionate staff will judge the entries and pick a winner every 2 weeks for the next 2 months. There are two remaining Red Sea and two more Maldives liveaboards to be earned, so get nominating and give that hero a reward for their amazing work!

Winners will be announced by 14th (Maldives) and 28th (Red Sea) of each month. Final entries for Red Sea by 20th May ‘21 and Maldives 5th June ’21.

Entries, comments and questions should be sent to heroes@emperordivers.com.

Terms & Conditions apply: Please contact heroes@emperordivers.com for details.

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Explore the amazing triangle of Red Sea Reefs - The Brothers, Daedalus and Elphinstone on board the brand new liveaboard Big Blue.  With an option to add on a week at Roots Red Sea before or after. 

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This trip will be hosted by The Scuba Place.  Come Dive with Us!

Call 020 3515 9955 or email john@thescubaplace.co.uk

www.thescubaplace.co.uk

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