The O.G.

“Ok, Kirstin, I’ve got it,” Kharis declared. “The O.G., Islands, and Chaos. Those are our names.”

I nodded at my graduate student. I had asked her to come up with code names that would be easy to remember for three corals we wanted to sample. Underwater, we were likely to confuse or forget the scientific names, so the codes made it easier to communicate.

The O.G. (Favites pentagona). The distance between the black
tapes on my scale bar is 20 cm. Photo by Kharis Schrage.

“O.G. for Orange Green?” I asked. She nodded in confirmation.

“How about Fat Fingers? Do you want to sample that one?”

Kharis shrugged. “Sure, why not. We have enough jars.”

In my head, I visualized each of the coral species one by one and assigned their new identifiers. Four species was a pretty ambitious goal, but if Kharis was up for it, so was I.

It took us about 4 days to collect all the samples, but we did end up getting enough replicates of each species. We worked out an extremely efficient system underwater. I would lay the scale bar next to a coral I wanted to sample and break off a piece with my fingers. Then Kharis would come behind me, put the nub in a labeled bag, photograph the colony, and give me back the sample bar. At one site, we collected 60 samples in a dive that lasted 62 minutes – just over a minute per sample.

The real work comes after we get home. I’ll use the four species we sampled in a genomic analysis to study patterns of connectivity among different populations. Some of you might remember that one coral, Porites lobata, has genetically distinct populations in Palau’s Rock Islands. One of the populations is tolerant of higher temperatures and therefore resilient to bleaching. It also occurs more frequently in semi-enclosed lagoons. Well, I wanted to see whether other species have similar patterns. Do they have distinct populations inside and outside of lagoons? Do the connectivity patterns match what we would expect based on oceanographic modelling of larval dispersal (they don’t for Porites lobata)? Are there different connectivity patterns for species with larvae that disperse in the water column for different amounts of time? Hopefully, my analysis will answer these questions.

Fat Fingers (Porites cylindrica). Photo by Kharis Schrage.

Sampling 15 replicates from 4 different species at each site sounds like a lot, but our samples are actually really small. Each bit of tissue is just a few square centimeters. We know the corals can recover from this small-scale damage because they sustain it all the time – our samples are about the same size as a parrotfish bite. We saw some parrotfish scars on the reefs we were sampling, and the similarity to our sample scars was clear.

I’m pretty proud of us for meeting such an ambitious goal in a short amount of time. The analysis at home will be fun!