Caldeira Lab

Influence of sea cucumbers on a coral reef CaCO3 budget: Kenny Schneider

Click here to read about the paper



Q = Caldeira, A = Schneider

Q: So Kenny, we were here on One Tree Island about two years ago, and we noticed from geochemical measurements of the sea water that the reef was dissolving at night. You set about to study possible factors that might be causing this.

A: Yeah. We were observing, we noticed that there were a lot of sea cucumbers in the area. And we knew that their basic physiology because they basically engulf calcium carbonate rubber, and just this goes through their gut system.

Q: Wait. You said calcium carbonate rubber?

A: Rubble.

Q: Rubble.

A: Grains of sand and stuff like that that has a bunch of--it’s coated with organic matter that they basically eat this organic matter, but at the same time because the gut is acidic, so they have the potential to dissolve calcium carbonate. And so we were wondering, because the population was so dense, and we were wondering if they could have some sort of effect on the calcium carbonate budget there. Finally, we were very surprised to see that their effect is much greater than anybody expected or knew about it. Once we budgeted for an entire day, we calculated that they have a potential to attribute up to about 50% of the calcium carbonate dissolution at night, which as you can imagine, it’s a big part of the reef’s calcium carbonate budget.

Q: So did you come to One Tree Island planning to do this experiment? How did you do this work?

A: No. This work is actually, it’s some scientific experience from previous work, but it’s also a lot of luck because there was another group who was from Maria Byrne’s Lab that was--they’re expert in sea cucumbers. They actually did the collection for us, and we did the geochemical incubation and calculated the fluxes of calcium carbonate. They also did for us the ecological survey to understand how many--to quantify the number of sea cucumbers in the area there. That’s actually a very nice interdisciplinary approach with people who come together and figuring out the common question. I think it’s a beautiful approach. I actually like the paper. [laughs] It’s not something that’s planned. That’s something that only can happen on an island. And when you actually find and introduce yourself to interesting people who actually listen and talk and get an idea, and basically the incubation was so simple, we didn’t need to organize anything. We had everything on site.

Q: So it’s bringing together some biology and geochemistry to understand processes that might be important for global change.

A: Yeah.

Q: So one big concern about this reef is that carbon dioxide emissions is leading to ocean acidification, and that might cause the reef to start dissolving, perhaps even within a few decades. So one question is whether the amount of dissolution caused by the sea cucumbers is going to increase as ocean acidification increases. Do you think there’s anything that could be done to investigate that?

A: We did it this time. We did a follow-up to actually answer this question. But my basic belief would say that the sea cucumber gut is a biologically controlled system. Probably ocean acidification won’t affect, won’t change their ability to dissolve or not dissolve calcium carbonate, but you might think of a reef itself growing less and they still doing the same amount of calcium carbonate dissolution than the reefs might be consumed a bit more than today.

Q: So you think that these sea cucumbers control the chemistry inside of their digestive systems, but that as the reef grows more slowly the relative importance of this digestion would get bigger.

A: Yeah. I think that’s true. But preliminary result today that we have from this one does see that they are probably calcifying less, but that’s still to analys--to do a full analysis of the data.

Q: We’ll look forward to that analysis, and I’m sure it will appear in another paper. So we’ll look forward to that also.

A: Yeah, thank you very much.

Q: Thank you.

Schneider, K., J. Silverman, E. Woolsey, H. Eriksson, M. Byrne, and K. Caldeira (2011), Potential influence of sea cucumbers on coral reef CaCO3 budget: A case study at One Tree Reef, J. Geophys. Res., 116, G04032, doi:10.1029/2011JG001755.

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