Davidson Expedition, January 26 - February 4, 2006
January 30, 2006
Davidson Seamount Expedition Log: Day 5
NOAA/MBARI Objectives: Biology transects, measure currents, water samples for organic matter, and biology collections in the deep north east “Red Crescent.”
We started the day in a deep valley on the northeast end of the Davidson Seamount, at a water depth of 2800 meters. Swift currents, even at this depth, seem to bring nutrients to a surprisingly diverse coral and sponge-dominated assemblage. Upon touching down we saw a variety of invertebrates that we immediately began sampling. We found several large enteropneusts (a hemichordate), a large sabellid worm, several Lepidisis bamboo corals (see image to right), a stalked sponge, and many small gastropod snails. Nearby, we found sediment as we had expected and then push-cored the gravelly substratum along with an unusual pink sea cucumber.
We continued across the valley floor and then began ascending a steep talus slope where we encountered several beautiful species of black corals, unusual sponges, Chrysogorgiid corals (see image below), and a multitude of yellow stalked sea lilies (see image to the left), reminiscent of the Truffula Trees from Dr. Seuss’s "The Lorax." Moving along, the cable above ROV Tiburon encountered currents which were so forceful that it had difficulty heading to our next target.
After several hours of slow progress towards the cone at 2300 meters, we finally reached the summit where we encountered currents of such high velocity that we were able to touch down only long enough to measure current speed and grab a rock for MBARI’s Volcanology lab. The terrain at the summit consisted of pillow lavas and talus. The biota consisted mainly of the crinoid Florometra, lithodid crabs, and sea cucumbers. We were surprised by the lack of corals at the summit of this cone, as we had expected to find a lush coral garden as has been the case on other, shallower summits.
- Lonny Lundsten