Posted by graduate student Alison Sipe, University of Delaware College of Marine Studies.

The last couple of dives have led to interesting findings. The biologists are very excited about the possibility that they may have discovered a previously undescribed symbiosis. A red polychaete worm about 5 to 6 centimeters in length was collected from the vents. Tim Shank identified that the species belongs to the family Polynoidae. He and Craig Cary were intrigued by the great number of large white setae on the worm. Setae are hair-like structures that line the length of the worm’s body and are used for slivering through the muddy bottom.

Almost immediately, the thought crossed Craig’s mind that the prominent setae may actually be covered in bacteria. There are quite a few symbioses between hydrothermal vent worms and bacteria, so it would not be surprising to find such an association. Craig snipped off a few setae, stained them with a fluorescent dye, and viewed them under the microscope. Based on his initial crude assessment, he thinks the cells may actually be bacteria. He plans on looking at the structures more closely when he returns to the University of Delaware and uses his special microscopes. This was a very unusual specimen in their collection, for it was the only one sampled so far during the cruise. Hopefully, they will be lucky enough to find another.

As I have alluded to before, the science party has been frustrated with the sediment cores they have collected. George Luther’s laboratory, including post-doctoral fellow Tim Rozan, will use electrochemical techniques to characterize the chemical environment of the sediments. They insert their special sensor probes vertically through the sediment layers and measure the chemistry at different depths of the core. As is usually the case with sediments, there are distinct zones or layers that have different chemical compositions; therefore, it is important that the layers be preserved while remaining in the cylindrical sampler.

There have been many interesting methane-producing bacteria in these sediments, which the microbiologists are thrilled about. However, these methanogens produce gases that bubble within the core and disrupt the sediment layers. To solve this gassy problem, the scientists planned to sample less methane-rich sediments — this strategy was a success because the cores they collected remained undisturbed throughout the dive.

The scientists are working with the cores this evening. Much to the dismay of the rest of the ship, the sediment cores are super-stinky! They contain high levels of hydrocarbons (diesel fuel) and sulfides, both of which have smelly odors. The hydrocarbon stench overwhelms the sulfide odor, although Tim comments that the talented nose is able to discern both smells. I am not sure I’d care to learn that skill.

Alice Ortmann is excited with the results of her marine virus experiments. Viruses get a bad rap, because we usually associate the word “virus” with nasties that harm humans. But viruses are everywhere in our world — most of them don’t even bother humans at all. The oceans are teeming with marine viruses that play an important part in the marine ecosystem. Surprisingly, no one has reported on whether there are viruses living at the hydrothermal vents. Are there viruses? How many? Where are they? Do they like the super-hot vent fluids, or do they prefer to hang out in the cold water?

It turns out that Alice has found many viruses in her water samples taken near the vents. She still needs to analyze her data by plotting graphs on the computer and correlating these numbers to the sampling areas and temperatures. No doubt, she will be glued to the computer screen doing her analyses during our transit to the mainland. It will be interesting to see the story she tells based on her results. Two brilliant pink spiny spider crabs have been collected from the vents during the cruise. These crabs measure about a foot-and-a-half across when their legs are extended. There are thousands in the Guaymas Basin vents, but they are challenging to collect.

One of the crabs was a gravid female, meaning that she was toting hundreds of eggs in her carapace. The eggs look like a palm-full of blackberries, but were connected to a stalk such as grapes are. The vent biologists took a couple of samples of the crab’s leg tissue, which will allow them to examine the DNA for systematic examinations (species identification) and determine what foods they are eating using special isotopic experiments. Craig Cary and Tim Shank have arranged to donate the male crab to the Smithsonian Institution when they return to the States because they believe that the museum does not have a good specimen of this crab species.

Tomorrow is the final Alvin dive of the Extreme 2000 cruise. Post-doctoral researcher Dorothee Gotz and marine chemist Don Nuzzio will be diving in the sub with pilot Blee Williams. The scientists and Alvin pilots have grown increasingly familiar with the Guaymas Basin vent terrain and can quickly maneuver from site to site. The submarine dive will be moved ahead one hour earlier tomorrow, because as soon as the sub surfaces at the end of the day, the R/V Atlantis will start cruising for the mainland and the port stop in Manzanillo. The sky will still be dark and speckled with stars when the sub goes in the water — a most spectacular show!