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Friday, March 14, 2003: Leg 3, Day #3

Farallon Basin

Today was one of those days you want to write home about. So I will.

We launched right on schedule at 0630. NavProc, the balky data integrating system that hamstrung us yesterday worked beautifully today. We descended straight away into another shallow layer of Bathochordaeus, the giant larvacean that lives at least 100 meters deeper in the well-oxygenated waters of Monterey Bay (see image). These observations served as a cue for today's blue-water scuba team Steve Haddock, Kim Reisenbichler, and George Matsumotowho collected several specimens by hand and brought them back to the ship. Bill Hamner then set them up in small glass chambers and watched as one of them began to build a new filtering structure, or "house." This process has been a mystery to us ever since we started working on these animals several years ago. Well, of course it didn't work out the very first time we tried, but we have some good new insight into the process and how to set up an experiment aboard the R/V Western Flyer that will let us watch a house being built. So, tomorrow or the next day we hope to be documenting house construction in the field and in the lab.

Meanwhile, back in the control room, we were assessing the animals we passed during descent, constructing a vertical profile. We will compare the profiles we record in three of the Gulf's basins  with each other and with our reference community in Monterey Bay. The critical factor in these comparisons will be oxygen concentration, which  has a major influence in determining where animals live in the water column. It's very early yet, but we are already seeing differences. More and different fishes yesterday than today, and at different places in the water column. A different mix of gelatinous species in the near-surface layers. Distinct benthopelagic faunas at each of the two Gulf sites we have examined. We expect that as our measurements become more extensive some of these apparent differences will fade while others will become more distinct. From these comparisons, we hope to learn more about the factors that influence the composition and structure of midwater communities. 

Sometimes, when you least expect it, things come together in surprising ways. Expeditionary research can be like that; you don't always know exactly what you are going to learn, but experience has shown us that the effort always pays off in the long run. Today, at 2,917 meters deep in the Farallon Basin two separate and unrelated lines of research suddenly intersected. Holy Smokes, nobody expected this SPIDERS EAT SINKERS!

For years Kim Reisenbichler, Rob Sherlock, and I have been measuring the amount of organic carbon that is transported to the deep-sea floor by discarded larvacean housessinkers. We were convinced, and our data confirmed, that this is an important energy pathway that has been overlooked by conventional sampling. The missing piece of the puzzle was direct evidence that the sinkers are consumed by animals at the bottom. This afternoon, as Karen Osborn was guiding ROV Tiburon's dive and searching for spiders, she calmly reported one carrying a sinker, and then another, and another. Soon we were cruising just above the sea floor counting  spiders right and left, most of them eating what were unmistakable sinkers. I'd like to say that we all reacted to this important and happy discovery with appropriate professional decorum but we didn't.  

Tonight the Western Flyer is heading back to La Paz. We finally got word that our lost trawl net is  found. The ship's crew will pick it up, along with an oxygen regulating valve for Brad Seibel's respirometry equipment, very early tomorrow morning after a trip to the inner harbor in our RHIB boat. The transit will eat up about 16 hours  so we probably won't be back on station until tomorrow afternoon. We'll try to get in a short, shallow dive then to test Edie Widder's low-light camera and a new idea of Bill Hamner's for how to accomplish video transects in the uppermost part of the water column.

This was a busy, happy, and very successful day that I've only partially documented. Everyone is working hard and working well together. In future updates, you will hear from some other reporters, in order to provide some different perspectives on the cruise. Stay tuned...  

Bruce Robison

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