Whale Fall Cruise
August 6, 2003 - August 8, 2003
Wednesday August 6, 2003
Jennifer Trask and Bob Vrijenhoek write: Today we used Tiburon to visit the carcass of a dead whale that had fallen to the deep canyon bottom. The nutrients that the carcass brings to the seafloor allow an entire community of animals to grow quickly and take advantage of the new habitat.
We found the whale carcass in February 2002 while we were exploring the seafloor in search of clams. Still covered with plenty of soft tissues, the whale most likely died less than six months before our discovery. Marine scavengers like hagfish would normally devour the fleshy parts quickly, but these fish can't live in the high pressures found at 3000 meters. The whale carcass was therefore decomposing more slowly than it would have at a shallower depth.
We used DNA sequences to determine that the carcass belonged to a gray whale. We extracted DNA from a small sample of baleen (the tough substance whales use to strain food from the water), and compared the sample's DNA sequence to those from known whales. The sample DNA closely matched the DNA from gray whales. We concluded that the whale was a juvenile because its length was only about 30 feet, and adult gray whales grow much larger.
When we visited the whale again in October 2002, we found the carcass picked clean - no fleshy parts remained. The area around the carcass was populated with squat lobsters, crabs and sea cucumbers. An octopus had made its home in the bone at the rear of the whale's skull, and below the octopus we found a large pile of crab parts, likely remnants of its previous dinners. The most remarkable organisms we observed, though, were thousands of red tubeworms covering many of the bones like a thick carpet. Working together with a worm specialist, Dr. Greg Rouse, from the Australian National Museum, we learned that these worms were very unusual, having no mouth or gut. DNA sequencing and anatomical comparisons indicated that the worms were distantly related to the tubeworms found at deep-sea hydrothermal vents.
We returned to the whale again today (whale vertebrae at right) with Dr. Rouse aboard as a guest scientist. He was very excited to see the worms alive and in their native environment. We recovered many of the worms and now have them in the lab on board the ship where we can photograph them and prepare them for more detailed studies. We would like to learn how they survive on whale bones, although we suspect they may depend on symbiotic bacteria for nutrition. (see worms at left below the anemone and crab)
Other MBARI participants on the cruise are Shana Goffredi, Joe Jones, Robbie Young, Shannon Johnson, Yvette Alva, Jeannette Fink, and MBARI interns Jennifer Trask and Melissa Duhaime. Everyone is busy this evening picking through the mud and bone samples that were collected on the dive. Tomorrow, we will launch Tiburon early in the morning so we can have a full day to explore the whale for more interesting animals!
- Jennifer Trask and Bob Vrijenhoek