we set sail from Pichilingue at 8:00 a.m. for our first dive site located
between the peninsula extending north from La Paz and Isla Espiritu Santo.
The passage out of Pichilingue is rimmed with rugged volcanic rocks, and
in the shadows of the early morning sun, the outline of the craggy
ridgeline was sharply defined (see above).
We arrived on site at about 10:30 a.m. and proceeded to dive to a
depth of about 720 meters. A muddy seafloor greeted us, and we proceeded
up slope towards the mouth of the channel between Isla Espiritu Santo and
the mainland. During early afternoon, we encountered hard rock outcrops
and collected a suite of samples for later identification and analysis.
After passing through this zone of hard, granite-like rocks, we
encountered more muddy seafloor. We found few benthic organisms, and
instead some scattered shells. A few very small patches of bacterial mat
dotted the seafloor landscape.
As the dive continued into the afternoon,
we encountered a hummocky bottom that had more burrows. Seafloor life
became more abundant. We passed through a broad swath of seafloor rich in
frilly sea pens, and we found increasing numbers of crabs and shrimp in
their burrows on the seafloor. The increase in abundance of
seafloor-dwelling organisms we observed is consistent with the
well-established change in the oxygen concentration in the bottom waters
of the Gulf of California. Although depths vary around the Gulf, there is
an oxygen minimum zone that spans roughly 400 meters to 700 meters water
depth. The seawater in this zone has been stripped of its oxygen by
vigorous decay of organic material raining down from the photic zone down
to the seafloor. Where this oxygen-depleted
zone of ocean water impinges on the seafloor, little oxygen is available
for organisms that respire. Thus, great expanses of the seafloor within
the oxygen minimum zone have reduced numbers of organisms because of the
dearth of oxygen.
While the dive progressed during the afternoon, it became apparent that summer is beginning to descend on La Paz. The heat and humidity reminded me of a sultry summer day along the east coast of the U.S. Isla Espiritu Santo became shrouded in a summer-time haze (see above). At 2:00 p.m., we had our standard fire and boat drill. The scientists mustered in the science lab, and we reviewed safety procedures, ship’s bell signals, the station bill, and how to put on a survival suit. One item that we are expected to bring to a fire and boat drill is a hat. Unfortunately, Dave Caress couldn’t find his in time, so he improvised (see right). I think he might be setting a trend in nautical headgear. After the safety briefing, we all returned to the cool, dark recesses of the control room. Today’s dive ended in a water depth of about 250 meters. Once ROV Tiburon was on deck, we immediately set sail for our next dive site, which is offshore from Loredo. It will take about 12 hours to reach the site. While unloading the core and rock samples we collected today, Charlie Paull went scavenging in the sample drawer on Tiburon and made a discovery that brought a big smile to his face (see below).
Charlie Paull is delighted, bagging his first-ever rhodolith.
A number of you have been asking about Pinkie. Where is Pinkie? Little has been heard from Pinkie for the past week. Is she still on the bottom tending to her garden? Or will she emerge from the deep sea? Stay tuned for further adventures of Pinkie.
Today, compliments of our roving
reporter, we have another mystery photo. Can you determine what the
ship’s crew is doing to those big white things? Answer tomorrow.