Easter Microplate Expedition
March 24, 2005 Day 13
Please visit the ChEss website for additional information and translations in Español, Português, and Français.Alvin dive# 4090, 38°S. Victoria and Jessica were the observers and Pat was the pilot. The weather was mostly overcast with rain squalls. It was blowing 20 knots from the north, causing steep, choppy waves on top of the long swells from the SW.
Image: Galatheid crab perched high on a sulfide chimney.
The three previous vent sites were visited again today. They started at Sebastian's Steamer, still spewing and building new sulfide. Water samples for microbiology were taken above it. They went on an unsuccessful brachiopod hunt, but found some stalked barnacles and sampled floc emanating from a diffuse vent. At Pâle Etoile they collected mussels. This is a less active site than Sebastian's Steamer, with diffuse venting from around an inactive sulfide spire covered with mussels (pictured in the March 22 update). There was clam shell hash, so it probably was well populated with clams at one time. Some mussel shells appeared to be blackened, perhaps singed.
They continued to the third site, as yet unnamed. On the way they collected some urchins that may be a new species and saw numerous fish (probably family Ophidiidae) that may be a new species that Michel is describing from
17°S. The third site is in a fracture, like a small ravine, with large lava pillows, swimming crinoids, and many white, hairy galatheids. Mussels were collected and with them a small piece of the sulfide chimney to which they were attached. The bacteria from the chimney will be cultured, and on a cross section of the chimney there will be molecular work, microscopy, and isotope analyses on a profile from the inner part where there is active flow to the outside.
Victoria has worked a lot with ROVs, but she found it made a huge difference to be in the Alvin. She felt that she could interpret distance and dimensions better seeing the seafloor in three dimensions, and enjoyed seeing the bioluminescence.
Alvin pilot Tony working in the Top Lab during the
dive. The Top Lab
is up near the ship's bridge, and is where Alvin progress is
monitored and communications are received over the underwater phone.
The underwater phone uses sound waves much like FM radio uses
electromagnetic waves: the carrier frequency of 8.1 kHz is
frequency-modulated to broadcast the signal through the water column.
You can hear it through the ship's hull, and it sounds like an electric
buzzing or a hummingbird call.
From the Chief Scientist:
We have completed a four-dive series on the vents at 37° 48' on the Pacific-Antarctic Ridge. We have successfully collected samples of mussels, palm worms, snails, crabs, limpets, and other typical vent species. Unfortunately, we have not been able to collect Riftia tubeworms or giant Calyptogena clams, though a shell from a dead clam was recovered today. We've done all the work we can do at the present site, so we are moving about 13 kilometers (8 miles) to the north, to 37° 40', to investigate a feature of the ridge that was previously shown to have thermal anomalies. Nicole and Shana will dive tomorrow with the goal of finding clams, tubeworms and new active vent sites.
Jessica receiving her first-timer's due. A very wet and happy Victoria, also a first-timer, with Bob after her dive.
There are no published accounts about juveniles for worms of the genus Alvinella, so this may be the first time juveniles have been found. Some development data is available for the other genus of Alvinellidae,
Paralvinella, and so some comparative analysis will be possible.
Left image: Limpets on the abdomen of a crab. Right image: Juvenile Alvinella (3mm) found in tube of A. pompejana adult. Photo by Greg Rouse, South Australian Museum.
All underwater photos were taken with the submersible Alvin, and are courtesy of Woods Hole Oceanographic Institution.