south. Sometimes you eat the bear—sometimes the bear eats you.
The wind picked up again last night and
though we hung around, hoping it would moderate, by midday it was clear
that we had no chance for another dive in Carmen Basin. So we are steaming
toward our next dive site, a little east of Cerralvo Island and a little
west of Cerralvo Bank, where we made our first dive on the midwater leg of
the Expedition. For lack of a better name, we are calling it Cerralvo
Trough. It has the advantage of being the deepest spot close to La Paz,
where we must be by 1600 hours tomorrow afternoon. Underway we have a
following sea and the wind behind us, so it seems as though the R/V
Western Flyer is really flying. She's the only one because the
birds must be walking today.
How can you know where you are if you’ve never been anywhere else? Comparative research is kind of like that. By comparing characteristics in two different places you can learn what’s similar, what’s different, and why. Monterey Bay is our reference community for midwater research. When we study the Gulf of California with its pronounced oxygen minimum layer, we
see that many familiar animals, like salps
and larvaceans, live very much closer to the surface in the Gulf than they
do back home. We think this is because the oxygen minimum zone comes so
close to the surface here, that animals which are intolerant of low oxygen
are squeezed upwards into a narrow band of water near the surface.
sort of pattern tells us that similar ecological niches must exist for
salps and larvaceans in both places. When these patterns are repeated again and again, we begin to
think that maybe we are seeing a piece of the fundamental structure of
midwater communities. We can also learn about the effects of certain
environmental parameters, oxygen in this case. We see that salps and
larvaceans are apparently displaced by low levels of oxygen, but we also
see that other species, like the myctophid fishes and many small medusae,
manipulation is a traditional approach for conducting biological research.
But in most cases, the ocean is just too big to manipulate, especially the
deep parts. So in order to get that kind of information, we look for
naturally occurring variations in the parameters we want to examine. To
study the influence of oxygen, we go to the Gulf. To study the role of
temperature, we go to the Antarctic, where the water column is virtually
the same temperature from top to bottom. To study the impact of low
productivity, we go out into the central Pacific Gyre. For this approach
to work, it helps to have a reference standard, and for us that's Monterey
plan is to begin our dive at 0400 hours tomorrow morning, dive until 1100
hours, and then head for the beach. Last communiqué tomorrow...