Easter Microplate Expedition
April 5, 2005 Day 25
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Alvin dive# 4098, 26°S
Robbie and Victor were the divers and Pat was the pilot. The weather finally improved and we got a dive here at 26°S on the east side of the Easter Microplate!
We dove today on a site that we hoped would have active venting. When we reached the bottom, we saw pillow basalt (image on right) with very little biology around. The plan was to climb to the axial summit and follow the summit south to look for signs of hydrothermal activity. When we reached the summit, all we saw was constructional pillow basalt. The flow appeared to be pretty young, maybe a couple of years old. We followed the summit south for a while, and then decided to return to the axial trough to follow a fissure that we saw earlier in the dive. We found the fissure and followed it south until it ended. It was about 10m deep, and you could see pillows that had been ripped in two on either side of the fissure. It is quite impressive to see these fractures and to imagine the forces that create them.
We had still seen very little biology so far. There were a few lonely shrimp, a sea cucumber, and a couple of Cerianthus anemones, but that was it. This was the most barren bottom that I have seen so far. We did see some hydrothermal staining on some of the rocks suggesting that water had been flowing, but there was no evidence of active flow now: no bacterial mat, no shimmering water, no vent animals. Not even a single crab! We finally came upon a stalked crinoid, and we collected it for Greg. We continued to head south following fissures. Some were large enough for Alvin to fit in, others were a bit smaller. We collected some basalt and some water for microbiology. Our batteries eventually ran low (after about 3.5 km) and we had to surface.
Left image: Nematocarcinus shrimp. It is not always associated the hydrothermal community, but it finds a ready food supply in this biologically-rich area. The head is 1cm. Right image: A representative of a group of crustaceans not commonly seen: Nebaliaceae. The field of view is 3mm. Photo by Greg Rouse, South Australian Museum. Photos by Greg Rouse, South Australian Museum.
We ended up not finding any evidence of active venting. As it turns out, there were limpets that came up as by-catch with the basalt sample. So maybe in time, a thriving community will develop somewhere on this bottom. Or maybe a kilometer down-axis there is a thriving hydrothermal community that our batteries couldn't quite reach. Maybe next time.
It's been five years since my last Alvin dive (9°N on the East Pacific Rise). Gavin, who had his first dive as pilot on this cruise, was my roommate then, in 2000. He was an intern with the Alvin group at the time, and I had just gotten a job at MBARI as a research technician. Funny how time flies when you're having fun. Hopefully, I won't have to wait five years to get to dive again. Alvin's kind of addictive, so be careful, or you might be out here some day.
These are polychaete worms that have an eversible proboscis held inside their body. They use it to catch their prey, usually other worms or crustaceans. The field of view is 6mm. Photo by Greg Rouse, South Australian Museum.
Alvin getting hosed off, disassembled, and exterior fiberglass panels scrubbed after this last dive of the expedition.
If it suddenly ended tomorrow I could somehow adjust to the fall...
So many nights I just dream of the ocean that I wish I was sailing again." ~Jimmy Buffett
Such a strange realization: the cruise really IS ending tomorrow! I can't wait to get home and see everybody on land, but I know that I will miss the Atlantis. The feeling of exploring areas of the planet never before seen by human eyes is pretty incredible. I really look forward to reading the science papers that come out of this cruise, since we are left with a lot of unanswered questions right now (the deep sea is certainly good for that!) Back in our home labs is where most of the research will really happen, so the big discoveries have probably hardly begun!
More stuff I'll miss (besides the inspiring in-synch thumbs-up signal from the Alvin swimmers on every launch- thanks guys!): the view! It is NEVER really the same every day, but a continuously changing gorgeous mix of blues and whites that I think makes a great picture-but I'm sure no one back home will want to see that many pictures of the ocean! I finally managed to get up for sunrise yesterday, which is quite a feat of determination for me. At first it looked like I had picked the wrong day, since there were rain clouds on the horizon, but then the sun rose above the clouds and put on a lovely show for us. I have to say, it was worth getting up extra early! Still, sunsets are much easier to enjoy. Last night we had a little sunset watching party out on the fantail... I don't think I'm the only one who will miss it!
And so now I'm signing off for the last time... but I learned a LOT and had a lot of fun on the way. I have new friends and new freckles (no sunburn! too much inside time!), and about as many pictures as my computer can hold. To everybody at home, see you soon!
Alvin getting disassembled, scrubbed, and hosed off after this last dive of the expedition. After we disembark on Easter Island, the ship heads to Manzanillo, Mexico, where a new science party will get on for their own adventure. Panorama by Dan Layton-Matthews, University of Ottawa/Toronto.
All underwater photos were taken with the submersible Alvin, and are courtesy of Woods Hole Oceanographic Institution.