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May 7th, 2003; Leg 5, Day #17

Today’s dives were structured the same as yesterday: coring transects in the morning and laser Raman in the afternoon. This pattern gives the lab an opportunity to process cores earlier in the day and for us to get to bed at a reasonable hour. The dive day starts early, at 6:00 a.m., and a skeleton science crew is always at the launch. We staff the control room continuously during the day with at least three science staff on duty at any one time. Generally our dives last until 7:00 p.m. 

We expanded the survey area today around Pinkie’s Vent and located a few isolated patches of chemosynthetic clams and a single live tubeworm away from any of the clam patches. Much of the dive effort this morning involved collecting a large number of short push cores. By collecting core over a broad area around the vent, we will be able to better characterize the origin and amount of methane in the sediment that is fueling the microbial communities just below the sediment surface. Occasionally, clams are collected in the sediment push cores. A portion of the light-colored shell of a Calyptogena sp. clam can be seen in the photo of a push core (see above). 

The pore waters extracted from these sediment cores are analyzed shipboard for sulfate, chloride, magnesium, calcium, and methane concentrations. Some of the cores collected today had very high concentrations of methane, and often when the gas expands on the way up to the surface, bubbles disturb the sediment and form what is referred to as a moussy texture (see right). This can be seen in the photo of the surface of a push core being sampled in the lab. The microbiological analyses that will be conducted back at MBARI in Ed Delong’s lab will identify the types of microbes and their relative abundance. By late evening, we were swimming in samples. A peak into the lab refrigerator gives you an idea of how many samples we’ve already collected (see below).  

It was a difficult day trying to collect gas hydrate samples to analyze with the laser Raman spectrometer (LRS). The good news is that the new shutter that was installed during our port stop in La Paz is behaving beautifully. The new laser-fiber alignment mechanism that Bill Kirkwood, Larry Bird, and I constructed recently is doing a great job of providing us with consistent levels of laser power (~30 mW). Also, the replacement manipulator arm is behaving much more dependably, and, as usual, the pilots are doing a great job reconfiguring the ROV Tiburon mid-day for the LRS dive. These mid-day reconfigurations require the removal of the coring hardware and other small instruments, and the reconnection, testing, and installation of LRS gear before diving again. However, the nature of our work often dictates that SOMETHING must go wrong. For us it has been attempting to collect chunks of hydrate to analyze with the LRS. The equipment that we designed for this purpose was based on the observation of large pieces of hydrate floating off the seafloor at Hydrate Ridge, off the coast of Oregon. Unfortunately, at Pinkie’s Vent, the hydrates we stirred up from the sediment are very small pieces that float right through the small holes at the top of our funnel that is supposed to trap the hydrate chunks. 

You may be wondering why gas hydrate floats in seawater. Gas hydrate is analogous to water ice, both of which are less dense than seawater. When gas hydrate forms from methane-rich water, the water molecules create an expanded cage around a single molecule of methane, making the solid less dense than liquid water that contains dissolved methane. The alternate name for hydrate, is clathrate, which is derived from a Greek word for “claw.” So much for today’s etymological lesson in arcane scientific terminology. 

Tonight we have a special treat. An inspired, but anonymous, scientist on board composed this poetic description of today’s coring transects. With most humble apologies to Samuel Coleridge, here it is: 

As the new dawn unfolded, we caught vague hints of sulfide-tinged air. This portent spoke the ancient mariners truth, “Stink in the morn brings cores after dawn, stink after noon brings sleeplessness soon.” Tracking a transect line from the basin, crest, and slope of Pinkie’s newly established garden enabled copious coring opportunities, thus bringing truth once more to the veracity of sailor’s lore. With seven sets of three push cores, the mud people saw an active afternoon that settled into the wake of evening with a pod of pilot whales in lazy confederation passing by. Back at depth over ridge crest on the slope toward Pinkie’s Garden, all eyes beheld several small patches of chemosynthetic organisms. In one instance, a solitary tubeworm of the cold seep kind was spotted behind a lively bed of clams. As quick as Saint Nick and lickity split, the Tiburon moved to arms length of tubeworm and collected it whole for all to behold. And in the lab, the people sensed a cornucopia of mud, the kind that spans a fruitful spectrum between vintage sulfide and active sludge. What man, what woman could not find satisfaction in the act of pushing core and squeezing water from the life-giving matrix? What woman, what man could not find inspiration in the hope that one day we might know the microbial denizens of this murky methane jungle? As we push and plunge our way into the mysteries of inky sea, fall down into the dark recesses of ocean bottom, we cannot remain impassive, unmoved, devoid of introspection. Even a flamingo can find joy and self-awareness here. 

Good night,

Bill Ussler

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