How do marine mammals avoid the bends?

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

Date:  April 25, 2018

Source:  Woods Hole Oceanographic Institution

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.

"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.

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Scientists find Sea Turtles suffer from the bends like humans

It has been discovered sea turtles, like humans, can suffer from decompression sickness (DCS), also known as the bends.

The research, carried out by a team of international scientists, shows for the first time that DCS occurs in the loggerhead sea turtle. DCS was previously thought to only occur in humans and some whale and dolphin species.

Sea turtles are often caught accidentally in commercial fishing nets and those that appear to be active are usually released. This study suggests that these turtles, while appearing initially active, possibly have DCS and may die following release.

“This is the first time that the bends has been confirmed in a marine reptile,” said Dr Paul Jepson, co-author and marine vet at the Zoological Society of London.

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Deadly wind farms give bats "the bends", study says

Bats suffer from an airborne version of the diver’s condition known as "the bends" when they fly too near wind turbines, experts have claimed.

Concern for the welfare of the creatures has already prompted dozens of challenges to schemes in the Westcountry.

The RSPB lodged an objection against Somerset’s first multi-turbine wind farm at West Huntspill - which is was eventually dismissed by the Secretary of State but is now subject to a High Court appeal by developers Ecotricity.

The bird charity claimed it was in a “flight path” for birds and bats which could hit the rotor blades.

Now Queen’s University Belfast has unearthed another potential problem, namely that pressure from the turbine blades causes a similar condition as that experienced by divers when the surface too quickly.

Conservationists have warned that the bodies of bats are frequently seen around the bases of turbines, but it was previously assumed they had flown into the blades.

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