At this point we’re running on autopilot a bit. As one of the Georgia students pointed out earlier today, we’ve become incredibly efficient at the protocols, just in time to start heading home tomorrow.
People have also had time to start analyzing their data from the first round of experiments. Interestingly, the phytoplankton community has changed significantly in our little patch of ocean over just the short time we’ve been here. Brian commented “I always assume, incorrectly, that the system will be static throughout the cruise. But it’s not, it’s surprisingly dynamic every year”.
The phytoplankton are fatter towards the lower depths, indicating a stockpiling of chlorophyll to make the most of what little light penetrates to their level. The chlorophyll data back that one up. These fat phytoplankton started our trip farther up the water column, so each successive CTD we do we have to collect deeper to collect the same community of phytoplankton.
In addition, the grazer community has shifted over our time in the Sargasso. I’ll have to get back to you all with names and identities of the grazers in question, but let’s just say that we started with one ecotype and are now in another. Apparently, zooplankton communities are incredibly patchy as well as dynamic. Another bit of wisdom from the chief scientist at dinner was the ponderance about the patchiness of phytoplankton – the assumption is an even distribution across a wide geography, but there’s really no reason to expect that.
Further supporting the patchiness of the Sargasso was the mass of jellyfish that we floated through tonight. For about an hour about an hour after sunset, the current brought by a sea turtle’s dream of jellyfish, about 6 inches long each and spaced out about a foot between each one. It was like a net of jellyfish, and now one that’s been lifted. We didn’t see them the rest of the cruise, so not sure what caused the mass of jellies.
The discussion of patchiness and dynamism was enlightening because it’s one of those big debates in ecology that is still far from worked out. There is wide recognition among the ecosystem theorists that ecosystems are dynamic, even shifting between alternative equilibrium states, but then there’s the competing school of thought that a system is largely static unless a large disturbance comes in to shift things. The key part of this discussion is that it’s a debate among systems ecologists, one only beginning to sift down to the organismal and community ecologists, as evidenced by this cruise. It’s also a discussion that’s far from over and has huge implications for how to interpret data and create conservation policy based on the knowledge learned on trips like this one.
~Bluegrass Blue Crab