Palau paper number one

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This morning, I received a text from my collaborator and former postdoc, Hanny: "IT IS OUT!!!!"

The "it" in her exclamation needed no explanation. Neither did the ambiguous adjective "out." She was referring to the paper she had worked immensely hard on over the last several years. This paper is the first to report on our team's research in Palau, and I am immensely glad to see it in print. 

The story of this paper is a story of scientific women. It actually starts with Anne Cohen, another scientist at WHOI, whose lab had been going to Palau for years. They noticed that corals in the semi-enclosed Rock Island lagoons in southern Palau had fewer stress bands than other corals. They bleached less often. This was completely counter-intuitive, because the lagoons are actually warmer than the surrounding reefs. What could be the explanation? 

Hanny had an idea - she thought the genetics of those corals could possibly explain the differences in their bleaching history. When Anne's lab went into the field, Hanny swam behind the people who were collecting coral cores to look for stress bands and took a tissue sample from the exact individuals they had cored. That way, she could match a coral's DNA with its bleaching history. 

To learn all the DNA techniques she needed to use, Hanny turned to Janelle Thompson and Iliana Baums (also co-authors on the paper). With their help, she found that there were four different lineages of corals. A lineage is a group of corals that are genetically similar to one another. Two of the lineages bleached less than the others and were found primarily in the Rock Island lagoons. The results were astounding - it seems the corals had adapted to high temperatures. 

Porites lobata, the species we studied in our paper, forms the
basis for coral reefs in Palau. Photo by Kharis Schrage.
It was when Hanny gave a seminar on her research to WHOI's Biology Department that I entered the scene. The patterns Hanny had found in her coral populations did not match what I would have expected based on the oceanographic circulation patterns around Palau. Together, we realized that the next step was to look at the larvae. How far from home do coral larvae disperse? Where do they settle? Do some of them die shortly after settlement if the reef where they settled is too hot? Do they get used to being in the hot water over time? What drives the divergence between the populations?

To answer those questions, Hanny and I returned to Palau in 2018 to sample the youngest, smallest corals we could find. We collected little tissue samples just like she had before, except that this time, Hanny taught me the genetic techniques. Our results showed essentially the same as what she had found before - four lineages, two of which are more common in the lagoons. Furthermore, the juveniles that we had sampled were genetically similar and belonged to the same lineages as adults at the same site.

As often happens in science, the two datasets - adults and juveniles - got combined into a single paper. The timing was perfect, actually. Hanny had just decided to revise her paper about the adult patterns when we got results back from our juveniles. Combining them was a logical step. 

I am very proud of this paper, not just because it landed in a good journal, but because it shows some really important things. Thermal tolerance of corals is genetically influenced; the Rock Island lagoons in Palau harbor a genetic bank of heat-adapted corals; and at least in some cases, those corals can survive on outer reefs. I'm most excited because this paper lays the foundation for everything that my team is doing in Palau right now - studying the larvae and juveniles to understand the mechanisms that drive patterns in thermal tolerance across populations. We are also drilling down into the question of whether and how thermally-tolerant corals (juveniles and adults) survive on outer reefs. This research could ultimately inform coral restoration efforts in Palau and across the Pacific. 

It is so satisfying to see Hanny's work finally in print. You can find it in the journal Communications Biology: https://www.nature.com/articles/s42003-022-04315-7

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