Porites nubbin parts: part 2

Friends, I told you about drilling nubbins for a thermal stress experiment. Well, we actually used nubbins for something else too: a transplant experiment.

The crux of our research is figuring out what matters most - the genes you inherited from your parents, differential expression of those genes, or the environmental conditions you're exposed to. To separate those three factors, we need to run a transplant experiment. The basic idea is to compare corals that have different genes in their home environment and in a foreign environment. We'll keep track of who lives and who dies, what genes they're expressing, and how they respond to the environment around them.

Two of our sites presented an ideal design for a transplant experiment: Ngerur and Mecherchar. Ngerur is a small island on the western side of the Palau. Its shallow coral reef is exposed to the open ocean, so the temperature is relatively stable. Mecherchar, in contrast, is a semi-enclosed bay that rarely gets flushed with fresh water. As a result, the water tends to heat up during the day when the sun beats down on it. Mecherchar is a lot warmer and more variable of an environment. 

The "flute" nubbin rack at Mecherchar. Photo by Cas Grupstra.

The other convenient part about Ngerur and Mecherchar is that both host Porites corals that belong to two different lineages. They're genetically distinct, so we suspect they may have different inherent thermal tolerance. 

We collected corals from each site, drilled nubbins out of them in the lab, and then planted the nubbins back at the two sites. Half stayed at the site where they had been collected from, and the other half went to the opposite site. In 6 months, we'll come back, note mortality of any nubbins, preserve some to look at gene expression, and use the rest in a thermal stress test. 

I was pretty proud of how well our outplant design worked. We called it "the flute" because we made the rack from long PVC pipes with holes drilled through the top. Each hole was just the right size to wedge a nubbin into. Friction, zip ties, and epoxy should hold them in place for a long time - or at least, that's the hope. 

I'm very excited to see what this experiment shows!