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March 17, 2003: Leg 3, Day #6

Today's update on our expedition is provided by Rob Sherlock. After Rob finished writing, the winds climbed to greater than 45 knots, but the R/V Western Flyer sailed on and kept working.   

Guaymas Basin

Mar18_cucumber.jpg (29703 bytes)Today, for the first time since leaving port in Pichilingue 6 days ago, the Sea of Cortez felt like one. Until just two days ago, the seas have been glass flat and beautiful! Now the 15+ knot northwesterly wind has blown long enough to generate some small swell, just enough to remind us we’re on a boat. Although it has kept us from SCUBA diving, the wind has  not impacted our ROV “schedule.” Not a tactic often employed by us midwater folk, the value of a dive schedule is becoming apparent. Aside from several scientists aboard, all with slightly different interests, there are simply too many critters we haven’t seen before or have seen but which are slightly different—the buttworm, Poeobius meseres, familiar to us but…flattened on one end?! Or the medusa, Aegina sp., four-tentacled and swimming in small spurts as always, arms held up over its head but… it’s red! Or what 

looks like the eelpout, Melanostigma pammelas, common in Monterey Bay, but which we don’t believe has been found here. We’re not sure, and so we stare, wont to look at all of them.   

Following the more is better philosophy, we planned two dives today. We scheduled 4 hours to reach the bottom 1,968 meters below, two hours to search for missing equipment and exploring the benthic boundary layer and three hours to ascend to the surface, making collections if we have empty samplers. That puts us on the surface by 15:30 Mountain Standard time. After unloading ROV Tiburon’s samplers, the plan is to dive again, dropping like the benthic elevator to 1,000 meters. There we will begin bioluminescent transects using Edie Widder’s ISIT (Intensified Silicon Intensified Tube…from the department of redundancy department) camera. 

Similar to transects that we in the Robison lab have been running for about 10 years, hers do differ in that she quantifies bioluminescence. Where we light our transects with 4 beams that make those annoyingly bright halogens on your neighbor’s Miata look like candles, Edie’s transects are done in the dark. The black screen we watch her camera on is punctuated by brief, but often brilliant, luminescence. At 50 meters, we will follow dark transects with lighted ones to see who is up in the shallow waters. That these surface waters are rich in terms of abundance and diversity is no surprise since oxygen levels drop off so quickly throughout the Gulf. These are depths Bill Hamner is keen to explore. After transecting we will trawl, or so goes the plan. 

Post dive:

Mar17_elevator.jpg (40866 bytes)Today’s dive differed from yesterday’s only in that it does not lie over any hydrothermal vents or vent plumes. Both dives were made in the Guaymas Basin (GB). The idea is to compare the midwater fauna from both GB sites; particularly, those critters found in the benthic boundary layer some tens of meters off the bottom. Since we were there anyway, we took some time to search for a piece of lost equipment, an expensive device used to lift samples and samplers from the bottom independent of our ROVs. On a previous cruise, a bolt sheared at the surface and the benthic elevator took a one-way trip hasta la profundidad. We allotted two hours to find it. We needed only one. Thanks to accurate positioning and excellent estimation of drift (currents here are fairly strong) by the Captain, crew, and ROV pilots, we picked it up on sonar before we saw the elevator’s aluminum frame and white crates jutting up out of the mud at a 45 degree angle from where it had augured in after it’s 2,000 meter free fall (see above). Since it did not fit in one of our D-samplers we left it, GPS coordinates in hand. 

Organismal abundance and diversity differed noticeably from yesterday to today. Where yesterday we observed several species of medusa, ctenophore, and sea cucumber in the benthic boundary layer, today we saw fewer species at the same depths. Within the benthic boundary layer the lobate ctenophore, Bathocyroe sp. was easily the most abundant animal both days, however we saw fewer today. Correlation should not be mistaken for causation, and a sample size of two is too few. Still, in searching for patterns, it’s a start, and we have many more dives to go! Unfortunately, we were unable to make our second dive today. The compass on Tiburon’s tether broke. It is what the pilots use to count turns in the ROV’s tether. On retrieval a turn can quickly become a kink, so without a turn counter, we don’t dive. On the plus side, the extra time has allowed us to put the trawl in the water early and given me a chance to write a long-winded update. 

Although our purpose here has nothing to do with the expedition of Ed Ricketts and John Steinbeck, a journey that took place over 60 years ago, I confess that it is difficult not to keep them in mind. Toward the end of his log entry for March 17, 1940, John Steinbeck, disdainful of biologists who want to change an organism’s name essentially because it lacked political correctness writes: “At least we retain our vulgar sense of wonder. We are no better than the animals; in fact in a lot of ways, aren’t as good.” Our boat bears the same name as theirs. We sail the same sea. Even some of our emotions must have been similar—the thrill of potential discovery dampened by the fear of war. I am thankful that we, too, can find wonder in the creatures here and marvel even in the lowly buttworm. 

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