New research on deep diving marine mammals

December 21, 2011, Woods Hole Oceanographic Institute reports:

Source: Media Relations

Any diver returning from ocean depths knows about the hazard of decompression sickness (DCS) or “the bends.” As the diver ascends and the ocean pressure decreases, gases that were absorbed by the body during the dive, come out of solution and, if the ascent is too rapid, can cause bubbles to form in the body. DCS causes many symptoms, and its effects may vary from joint pain and rashes to paralysis and death.
But how do marine mammals, whose very survival depends on regular diving, manage to avoid DCS? Do they, indeed, avoid it?
In April 2010, the Woods Hole Oceanographic Institution’s Marine Mammal Center (MMC) invited the world’s experts in human diving and marine-mammal diving physiology to convene for a three-day workshop to discuss the issue of how marine mammals manage gas under pressure.  Twenty-eight researchers discussed and debated the current state of knowledge on diving marine mammal gas kinetics—the rates of the change in the concentration of gases in their bodies.
The workshop resulted in a paper, “Deadly diving? Physiological and behavioural management of decompression stress in diving mammals,” which was published Dec. 21, 2011, online in the Proceedings of the Royal Society B.
“Until recently the dogma was that marine mammals have anatomical and physiological and behavioral adaptations to make the bends not a problem,” said MMC Director Michael Moore. “There is no evidence that marine mammals get the bends routinely, but a look at the most recent studies suggest that they are actively avoiding rather than simply not having issues with decompression.”
Researchers began to question the conventional wisdom after examining beaked whales that had stranded on the Canary Islands in 2002.  A necropsy of those animals turned up evidence of damage from gas bubbles. The animals had stranded after exposure to sonar from nearby naval exercises.  This led scientists to think that diving marine mammals might deal with the presence of nitrogen bubbles more frequently than previously thought, and that the animals’ response strategies might involve physiological trade-offs depending on situational variables. In other words, the animals likely manage their nitrogen load and probably have greater variation in their blood nitrogen levels than previously believed.
Because the animals spend so much time below the ocean’s surface, understanding the behavior of diving marine mammals is quite challenging. The use of innovative technology is helping to advance the science.  At WHOI, scientists have used a CT scanner to examine marine mammal cadavers at different pressures to better understand the behavior of gases in the lungs and “get some idea at what depth the anatomy is shut off from further pressure-kinetics issues,” Moore said.   For other studies, Moore and his colleagues were able to acquire a portable veterinary ultrasound unit to look at the presence or absence of gas in live, stranded dolphins.
There’s still a lot to be learned, including whether live animals have circulating bubbles in their systems that they are managing.  If they do, says Moore, noise impacts and other stressors that push the animal from a normal management situation to an abnormal situation become more of a concern.  “When a human diver has some bubble issues, what will they do?  They will either climb into a recompression chamber so that they can recompress and then come back more slowly, or they’ll just grab another tank and go back down for a while and . . . and just let things sort themselves out.  What does a dolphin do normally when it’s surfaced?  The next things to do is to dive, and the one place you can’t do that is in shallow water or most particularly if you are beached.”
The Woods Hole Oceanographic Institution is a private, independent, non-profit organization in Falmouth, 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.

Pups on the beach

About a dozen pups are visible from the South boardwalk at Piedras Blancas. The first was born December 17. Re liable reports say additional pups have been born on beaches near the lighthouse. Although the beach isn't very crowded yet, two of the mothers were caring for two pups each already. As usual, a certain amount of confusion reigns.

This pup and his mother barked at each other, perhaps getting acquainted.

This pair were happily settled in.

Friends of the Elephant Seal are moving forward with plans to place a Webcam at the viewpoint. "We have reached our financial goal to place a live camera in the rookery," says the latest newsletter. "The equipment has been purchased and shipped to California State Parks personnel for installation. State Parks has informed us that they expect the installation to be completed early in 2012--in time for the peak of the birthing season. When the camera is installed, images of elephant seal behavior can be accessed by anyinternet-capable computer from anywhere in the world."

A Webcam is no substitute for being there, but it will be a welcome addition. Visitors who have been enchanted by seeing the seals can keep track of them from home, where ever that may be. And others who have never been to California can whet their appetite for witnessing this phenomenon.

More senior males arrive daily

Lat week's few have become many. This mixed group of males tussled with each other. The largest adults take little notice of the subadults as they wrangle on the beach. Perhaps they are conserving their energy or are too burdened by the weight of gravity to rouse themselves.

At least one female tried to settle on the beach, but the attentions of a subadult were more than she could endure. She escaped back into the water. After she evaded this one, an even younger male harassed her. She'll find a place for herself soon.

Ebony and Ivory

This pair seemed to be assessing the food possibilities of a large crowd of visitors.

S.S. Montebello

On December 23, 1941, the S.S. Montebello, loaded with a cargo of 73,571 barrels of crude oil and carrying 2,477 barrels of bunker fuel oil and an unknown quantity of lubricating oil, was torpedoed by a Japanese Imperial submarine and sank in federal waters. The wreck is located approximately two miles south of the Monterey Bay National Marine Sanctuary and is 6.5 miles off the coast of Cambria, California. It is completely submerged and laying upright in approximately 900 feet of water, adjacent to an un-named submarine canyon.

The National Oceanic and Atmospheric Administration (NOAA) funded two investigations (1996 & 2003) to assess the vessel’s integrity using a manned submersible. Several dives were conducted and the observations made concluded the hull was “remarkably intact” and the torpedo did not penetrate the cargo and bunker fuel tanks.

Robert Schwemmer, West Coast Regional Maritime Heritage Coordinator for NOAA Office of National Marine Sanctuaries, presented his historical research on the Union Oil Company tanker S S Montebello at a meeting in Cambria December 2. He also shared  underwater imagery of the sunken ship that sits in 900 feet just south of the Monterey Bay National Marine Sanctuary.  Schwemmer was part of the science team that rediscovered the wreck in 1996 in the two-manned submersible Delta.  In 2003, Schwemmer returned to the sunken tanker along with a science team from the Monterey Bay National Marine Sanctuary and State of California to continue the visual survey of the Montebello.   

In 2009, the Montebello Assessment Task Force was established at the request of California State Senator Sam Blakeslee to coordinate a risk assessment to determine the likelihood of a release of the cargo of more than 3,000,000 gallons of Santa Maria crude oil that potentially could be onboard. In 2011, the U.S. Coast Guard awarded a contract to Global Diving & Salvage to conduct an assessment of the condition of the sunken tanker and determine if the oil was still onboard.  Schwemmer served on the taskforce and was on board the OSRV Nanuq during the U.S. Coast directed assessment serving as a technical advisor.  “The history of the Montebello is still deeply rooted in the communities of Cambria, Cayucos and Morro Bay, for these citizens took heroic action to launch a sea and land rescue for the Montebello’s crew of 38.  Today, 70 years after the sinking, of the Montebello people are just learning about the little known history of Japanese submarines attacking and sinking American merchant ships within site of the California shoreline” said Robert Schwemmer

Schwemmer encouraged the community to seek listing for the site on the National Register of Historic Places. Perhaps to commemorate the 75th anniversary? He has helped retrieve this event from lost history. Such a listing would do Cambria proud.

Life on the beach

This young male showed up with a fresh cookie-cutter shark wound on his side on Sunday, November 13. It's a nasty wound, deep. Shows how these small sharks prey on the much larger seals. Although they are less than two feet long, they can take a big bite.

Monday, November 14 attracted more sea lions to the white rock for which Piedras Blancas is named than I've ever seen out there. 


Plenty of long-billed curlews on the beach.

Piedras Blancas weather

Weather varies dramatically along the Central Coast. Last Monday I left Cambria warm and sunny but Piedras Blancas was very windy. By afternoon, the wind was strong enough to blow coffee mugs off the sale table.

A local supporter living in state parks employee housing about a mile north of Piedras Blancas Light Station near the old PB motel has installed a weather station on the roof of his house, about 60 feet above sea level and 100 feet or so from the edge of the bluff above the beach. Data is posted up to the minute on the web site. The wind increased from 6 mph to 9 mph in the time it took me to write this post!

Thanks for this helpful information.