30 January, 2004

Dredge #3 was in the water at 2:00 AM, dragging across the second seamount in the cluster of seamounts that we started dredging yesterday. Dredge #2 from the 29th was a bit disappointing because of the small number of rocks that were collected and the rocks on dredge #2 were covered in thick muddy sediment.

When dredge #3 came on board, all of the contents were easily identifiable. There was very little mud on any of the samples. Cleanup was minimal. The contents of the dredge were easily separated into rocks and living organisms. Since the living things were so easy to collect, we put the rocks in one container and the "live stuff" in the other. It was a nice diversion for all of us to take a look at what had made the trip up with the rocks. Sam Mukasa speculated that the lack of mud and sediments might indicate that this volcanic feature is younger that from dredge #2. A younger seamount would conceivable had less time for sediment to accumulate than an older one.

The living organisms that were in the dredge were easy to separate and collect. We found a variety of starfish, brittle stars, sea fans, coral, and worm s and their casings along with the rocks in the dredge. After taking the organisms back to the hydro lab, we laid them out on the lab table to take photos. All of these organisms would have to be returned back to the ocean. Taking samples of any type from Antarctica into New Zealand requires special permits. These permits have to be acquired in advance. Since there were no biologists on this cruise, we didn't get a permit to transport biological specimens. Even without a permit, we took this opportunity to observe and catalog what we had "accidentally" collected during the dredge.

These organisms caught in the dredge had been living at a depth of about 600 feet. They live in the very harsh Antarctic environment, but they look very similar to their relatives that live in the temperate and tropical oceans. We collected two starfish. One appeared to be a juvenile and the other an adult of the same species. They did not have the distinctive suckers on the ventral side of their arms that are commonly seen on starfish in warmer climates. The body was nearly circular, like a ball of play dough that had been slightly smooshed. They are very interesting animals. Their skin was smooth with a leathery texture on both the dorsal and ventral sides.

The sea fans and brittle stars looked more like their typical warm ocean counterparts. The fans were a deep maroon, with variations from red to black. Each of the plumes was very delicate and extending from a thick base arranged alternately. The arrangement looked like how the stalks are arranged around celery plants, one inside the next. These organisms have very interesting ways of keeping themselves attached to the bottom. The tubeworms have a modified suction cup that has a may exert a vacuum hold on the mud or rocks. The sea fans have extensions at the base that look almost like roots even though they are definitely animals.

Even though the scientists are primarily interested in the rocks and geophysics of the area, we informally discussed the different animals that had been collected in the dredge. Marcy Davis was holding a solitary coral and said the last time she saw one of these it was a fossil. It could have been a distant relative of the one we caught in the dredge.

Following the dredge, we continued with the multibeam survey, moving south back into McMurdo Sound. The plan was to survey the area and get a feel for how much open water and how much fast ice was in the sound. The goal was to do a seismic survey of the area to tie together data that had been collected by US, Kiwi, and Italian geophysicists over the past twenty years or so.

Terry Wilson, Larry Lawver, Stuart Henrys and Sam Mukasa met on the bridge to discuss the plan for the next few days. After a bit of discussion about ice conditions, methods of doing seismic, and future areas to attempt dredging, a preliminary set of shot lines were identified. The scientist then discussed their ideas with the marine support staff to get their input.

A decision was made to use a different type of seismic streamer that collects data using one channel of data rather than many channels. This streamer is about 150 meters long, which is about a tenth as long as the multichannel streamer and can be operated using fewer guns. It can also be pulled in very quickly if the ice conditions get severe. The single channel streamer is also less likely to get caught and damaged in the ice.

Preparations were made for both the single and multichannel streamers. We continued to survey along the ice edge down along B15A, then C16 then along the sea ice along the cost of McMurdo Island. The views were spectacular as we cruised past Mount Erebus and in front of Discovery Island. As the ship rounded the ice edge, we were able to see the ice tongues of Terror Glacier and other glaciers on the eastern coast of McMurdo Sound.


Marcy Davis takes a look at the different living organisms that were brought up with dredge #3.

Picture of Mount Erebus from the ice edge of McMurdo Sound.

Large starfish caught in dredge #3. --

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