Porites

Most people who come to Palau are traveling for one reason: coral. The reefs in this small island nation are comparatively healthy and great for diving. In my case, the specific coral that brings me to Palau is called Porites lobata. If you’re not interested in the Latin name, you can call it “lobe coral” or “yellow mounding coral.”

Porites lobata. Photo by Kharis Schrage.

Porites is pretty cool. It’s extremely common on reefs in the Pacific, and it’s considered a pretty important ecosystem engineer. Porites provides the foundation for other corals to recruit and form a reef. It’s also less likely to bleach than some other species. Generally speaking, branching corals (acroporids) are highly susceptible to heat, while mounding corals like Porites tend to be more resilient.

In Palau, Porites is even more heat-tolerant than elsewhere. There are semi-enclosed lagoons in the southern part of the Palauan archipelago that get warmer than anywhere else. There’s not a lot of water flowing in and out of the lagoons, so they tend to heat up. Porites that live in the lagoons are exposed to warmer and more variable temperatures on a daily basis, so when an El Niño comes along and heats up the equatorial Pacific, they’re relatively unperturbed.

Scientists wondered for a long time how the corals in the lagoons could survive so well. A few years ago, a PhD student at WHOI named Hanny Rivera dug into this question and found that the heat-tolerant corals were genetically different from corals that were more susceptible to bleaching. Corals in the lagoons are actually adapting to the heat.

Some of you might remember Hanny. She and I worked together closely on a sampling trip to Palau in 2018. Together, we came up with the idea to take the research one step farther. What if heat-tolerant corals from the lagoons could send their larvae to the outer reefs? What if those heat-tolerant larvae could settle and grow on the outer reefs? What if they could make the outer reefs more resilient to bleaching?

One of the corals we sampled and tagged.
Photo by Kharis Schrage.

Those questions are the focus of my current research in Palau. There’s some really cool basic biology buried in the what-ifs – questions about life-histories and selection and adaptation to changing environmental conditions. My collaborators and I are definitely pursuing the fundamental biological questions, but I also appreciate that there’s an applied angle to this work. Depending on what we find, our work may have implications for the future management of coral reefs in Palau.

My grad student and I have been tagging and sampling Porites corals at different sites, both inside and outside of lagoons. Our goal this trip is to get as much background information on the tagged adults as we can – what genetic lineage they belong to and whether they’re male or female. That way, when my team comes back next year, we can collect exactly the corals that we want to spawn for our experiment. This is the reconnaissance mission; next year is the big operation. 

Long live Porites lobata!