Easter Microplate Expedition
March 20, 2005 Day 9
Please visit the ChEss website for additional information and translations in Español, Português, and Français.
Transit day 9:
Last day of transit! There are a billion last minute things to finish up before we start diving and the pace of life aboard ship changes dramatically. The estimated time of arrival is 00:30 tonight, just after midnight. It has been raining, and before breakfast it was very foggy, so the fog-horn served as an alarm-clock for many on board. At mid-day we altered course slightly so we could map with the multibeam sonar along the Foundation Seamount chain that intersects the Pacific-Antarctic Ridge at our dive site. When we arrive at the dive site, the decision will be made whether or not to deploy the transponders that assist the sub's navigation. The decision will be based on weather and sea state. Earlier today the swells were at about 2.5 meters (~8 feet), but they are predicted to be up to 3.5 meters (~12 feet) tonight, which may be too high to put anything in the water over the stern without the stern smashing down on it with the next wave. The same decision will be made for the Alvin at daylight.
Ana and Victor gave presentations about their research projects at the science meeting this evening. Ana, who is Portuguese, gave her talk in English, one of the many languages she knows. Victor gave his in Spanish, his native language, which many in the room also speak, and he had translated many slides into English so the rest of us had no problem following along. We have French speakers (Michel (a native speaker) and Cindy, Karen, and Ana), and German (Nicole a native speaker) among the science party, and one of the SSSG (Shipboard Science Services Group) techs who assists us with our science is Japanese. No Italian speakers sadly for me, but quite a multi-lingual group! Ana and Michel are kindly providing the Portuguese and French translations found on the ChEss version of this website so that we can reach a much larger audience. Thank you!
The REAL fun is about to begin:
The activity level is up around the science community on the ship because tomorrow morning Alvin goes in the water for our first dive! This afternoon Cindy, Megan and I ran through a "simulation" of the samples arriving on the surface. We will have to rescue our mussel pots from the science basket, and then collect the animals out, measure mussels, and put everything into preservative for sorting under the microscope. There are really about 40 more steps than that, but we're hoping our practice session will help everything go smoothly. We tucked our two mussel pots into the bucket quivers on Alvin's science basket, so hopefully they're completely ready to go. Wish us luck!
Jessica, Ana and Cindy making site markers in the lab. Photo by Megan Evans.
Jessica holding a finished marker. It is made from a paint-bucket lid and tied to links of metal chain. Photo by Megan Evans.
A tisket, a tasket, a very full basket:
One of the main issues in deep-sea biology is collecting samples in a manner that preserves the piece (whether a rock or a crab) for following studies. For much of our work, we need to collect discrete samples. We need to be able to tell exactly where and when a particular sample was collected. This seems trivial enough but there are some issues that make this considerably more difficult.
First, the scientist collecting the sample is not actually in control of the manipulator arms on the Alvin. Instead, the scientist is talking with the Alvin pilot while watching out of a different, small viewport or on a monitor. It takes quite a bit of coordination and communication so that the scientists and pilot are working to accomplish the goal of collecting a specific sample. A scientist cannot simply say "Collect that clam" and expect the pilot to know what the scientist has in mind.
Second, the issue of how to collect a sample must be decided. The size of the Alvin basket is roughly 1 meter wide by 1.2 meters long (~ 3 feet by 4 feet). Before the dive is even planned, an outline of equipment and placement of tools needs to be agreed upon by the scientists, pilots, and expedition leader. There is a fine balance between having too much and too little on the basket. If you take too much, even the most experienced pilot will have difficulty navigating and moving items between different compartments and boxes in the basket. As a consequence, a large portion of the bottom time (typically 5 hours or so) will be spent with the pilot rearranging equipment to get to the one piece that the scientists need to accomplish their goal.
Third, the Alvin, like most DSV and ROVs, has a limited amount of weight that it can bring up. Though the scientists may want to collect 500 pounds of rock and 100 pounds of mussels, that amount of weight would make it impossible for the Alvin to ascend to the surface for recovery. Thus, each potential sample must be carefully considered before collection because space/weight on the basket and time on the bottom both carry a high premium.
On the other hand, if you take too little on the basket, the scientist may not be able to collect as many samples as would have been possible if the drawer had been configured properly. That one extra biobox on the basket may make the difference in being able to collect a new animal species or a piece of sulphide chimney. Additionally, the basket is not something that can be changed once the Alvin is in the water. Then, whatever is on the basket is all that you will have available for that dive. If the scientists forgot to add a high temperature probe, no temperature measurements will be made of a hydrothermal vent on that dive. Careful considerations and double-checking everything immediately prior to the dive must be done to make sure there has not been any misunderstanding or assumption.
To meet the fine line of having too much and too little in the basket, one has to spend time coordinating between the Alvin pilots and the scientists. My goal has been to maximize the amount of samples we can collect on each dive while not making the basket too cluttered so that the dive is compromised. We are fortunate to have a very skilled Alvin group assisting us in making decisions for the basket. For the first dive of this series (#4087), we are targeting an area that should contain deep-sea mussels as well as some glassy basalt flows. To accomplish our goal of collecting deep-sea mussels for ecological and genetic studies, we will be using a combination of mussel pots and metal scoop nets to collect discrete samples. Samples collected with the scoops will be placed in one of the bioboxes. If we collect mussels from two distinct areas of the vent field, (i.e., black smoker versus diffuse flow) we may want to keep the two samples separate. In that case, we would need to put each sample in its own biobox. As you can see in the diagram for the Alvin basket (see diagram to left), we are limited in the number of discrete samples that we can collect using the bioboxes. To help increase the number of discrete samples that we can collect, we also have suction samplers which are connected by a 3/4 inch plastic tube to the starboard manipulator arm. The suction samplers allow us to collect smaller organisms as well as sediment and volcanic glass samples. We also have on the basket a hydraulic sampler that functions in a similar manner to the suction samplers except the strength of the pump is much stronger. This stronger pump will allow us to collect mobile crabs, fish, and shrimp which can easily out swim the smaller suction samplers. For geological samples, we will use the wax corers (WC #8 and 9) to collect small pieces of glass from discrete lava flows. To be honest, I find it hardest to separate discrete rock samples since many of the rocks will be very delicate. Rocks and glass are also the easier to contaminate between different containers.
As you can see, we have a very full basket on the Alvin even with nothing in it! It will be even more full when the
Alvin is brought back on deck full of rocks and mussels!
All underwater photos were taken with the submersible Alvin, and are courtesy of Woods Hole Oceanographic Institution.