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/Whalefall

2012 Nov 29

Skyfall by Bond. Whalefall by Virgin.

A year ago, the day before Thanksgiving, we got a unusual call – could we help pull a dead 70′ Fin whale off the beach in San Diego, CA, and sink it off La Jolla in 900 meters of water? The task was large, first to pull the whale to the site, second to bring and attach seven tons of steel scrap to send the whale down. We did it, and it was a terribly interesting day. From the massive ribs, visible at the necropsy, to the up close and personal experience of attaching the steel and helping to ventilate the carcass, Capt. Ahab style, it was a day of new challenges and learning for the team, and we succeeded – by the end of the day, “Rosebud” was on her way to the bottom.

Fast forward a year. Scripps has visited the whalefall site with their Remotely Operated Vehicle (ROV) and the scavengers have been hard at work. Almost all of the flesh is gone with just the skeleton left. The feeders would have started with sharks and then moved into eel like hagfish, rattails, then crabs, starfish, and shrimp. Finally, the bone marrow worms, one of the sea’s weirdest creatures, arrive and go to work on the skeleton itself.

On the web, whalefalls have been given credit for providing a food source for two years to decades. Rosebud has been consumed much quicker, with the remains down to the skeleton in just one year. Looking closely, the bone worms have started to arrive. These worms feed only on whale bones, with adults releasing a thousand larvae each day to float free, seeking another carcass to feast on. Since whalefalls are few and far between, it has to be one of the most optimistic life patterns on earth. And weirder still is the life process of the worms; the larvae that land on the carcass become females, develop and feast on the carcass, while the larvae that land on females become males and never mature past the larval stage, spending their entire life feeding on their yolk. Some of the males apparently fuse into the female bodies as well, leaving only their gonads on the outside to do their job.

http://www.mbari.org/twenty/osedax.htm

http://www.nytimes.com/2004/08/03/science/for-these-worms-an-immovable-feast.html

The photos also show how ROV’s are operated. The video screen information gives the depth, heading, and relative GPS location. On the skull photo the laser range finder is visible; the two lasers are set at an angle with a known range to intersection. Using the distance apart both range and a sense of scale can be derived. With power coming from a umbilical from the surface, the lights are bright and illuminate the scene well. Lastly, two lines can be seen rising from the skeleton; these go to glass floats about 40′ above the skeleton that were attached when we sent the whale down. The floats are very visible on sonar and allow the whale to be found much easier. At the same time, the lines are to be respected – they create entanglement risk for the ROV and its umbilical cord.

Photos courtesy Scripps, Eddie Kisfaludy

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