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Greek Origin
Word of the Day:
Eukaryote
from “eu” meaning good or true, and “kary(on)” meaning nut or kernel
Dipping into the DHABs
December 7, 2011 (posted December 8, 2011)
by Cherie Winner
A welcome sight greeted us when we got up Thursday morning—land! After a day and a half of rough seas and queasy stomachs, we had left the DHAB study area around midnight after the final deployment of Deep SID.
The little in situ sampler had performed so well at up to 1,000 meters that the science team decided to send it to 2,000 meters for another run of Maria’s grazing experiment. But that was too deep for an instrument not built to go to only 1,000 meters; just two of the sample chambers worked properly. Still, it was worth a try.
So were the repeated deployments of SID-ISMS on this cruise. Despite the problems it had, it brought back plenty of preserved samples for the scientists to analyze when they get home. Even its problems were valuable. They showed the scientists and engineers who designed the instrument what needs to be improved.
“It was a good shakedown cruise for the big SID,” says Craig. “I’m going home with a long list of things to work on.”
He says most if not all of the problems should be fairly easy to fix, like adjusting the size of the O-rings to compensate for how the rubber gets stiffer under extreme pressure in the depths. And once the changes are made, he’ll take it out on another cruise for another stern test of its abilities.
The sediment sampling work went more smoothly, but even using proven technology and instruments, the scientists found DHABs to be difficult habitats to work in. The multicorer hit bottom but couldn’t penetrate the crusty rock at the seafloor. Jason did a beautiful job collecting sediments from the halocline and the normal seafloor nearby, but had trouble getting all the way into a DHAB. The density of the brine was so high that the vehicle’s sensors actually thought it was on the seafloor, when it was just at the bottom of the halocline. But the Jason team kept trying, and finally was able to reach down into the murk with the remotely operated vehicle’s manipulator arms and collect pushcores of the DHAB sediment.
This means that for the first time ever, scientists have samples of DHAB water and sediments that were preserved in situ, right at their natural location. When they get home, each researcher will pursue a different aspect of DHAB biology. Chief scientist Ginny Edgcomb and Bill Orsi will examine preserved samples from the water column and sediments using fluorescent in situ hybridization and electron microscopy. This will help them determine what living organisms were present, and may reveal signs that these organisms have symbiotic relationships with bacteria. They will also study the preserved RNA in sediment samples to learn more about what organisms were alive in each sample.
Ginny and the team led by Thorsten Stoeck—post-doc Alexandra Stock, grad students Lea Weinisch and Sabine Filker, and technician Hans-Werner Breiner—will conduct focused studies of particular groups of protists.
Joan Bernhard’s lab (including Colin Morrison, who will come to WHOI next summer to continue the sediment work) will carefully examine the sediments for the presence of metazoans—animals—such as the loriciferans that were reported to be living in L’Atalante Basin (see Life in DHABs). Before seasickness set in yesterday, Joan scanned a sample from the bathtub ring with a dissecting microscope and found a nematode that had been living in the halocline sediment. Her group will use electron microscopy and other techniques to determine whether any metazoans in the samples were actually alive in the DHABs.
Kostantinos Kormas will examine the DNA of protists from the sediment samples to identify which species were present. During the cruise, he also gathered bacteria from the mats on some of the pushcores. They will be sent to another researcher, who will try to culture (grow) the bacteria in the lab so they can be studied in more detail. Hera Karayanni will work with Maria Pachiadaki on the grazing experiments, seeking to learn what organisms eat the protists that grazed on the DHAB bacteria.
But that’s when they get home. Right now everyone is packing up equipment and personal items, cleaning the labs and cabins, and looking forward to our safe return from an unusual but very successful cruise.
Bill Orsi created this video, which demonstrates the beautiful preservation possible when cells are fixed in situ in their deep-sea habitat before being brought to the surface. It shows a 3-D view, taken with a scanning electron microscope, of Cariacotrichea, a new class of ciliate that he and Ginny Edgcomb discovered in the anoxic Cariaco Basin off the coast of Venezuela. The single-celled protist is completely covered by bacterial symbionts. It was preserved in situ by Deep SID, the smaller of the two water column samplers used on this cruise.
