In my last post, I mentioned that I was continuing the project I started last summer at Lizard Island, Australia. That’s true, but in my haste to get a post out about my current trip, I neglected some important updates. First and foremost: thanks to an NSF grant through the Dimensions of Biodiversity program, our project is official, and we have a name! The Global Coral Microbiome Project, or GCMP. The team consists of members of the Vega Thurber Lab at Oregon State University and the Medina Lab at Penn State University. Along with more money and a bigger team, the goals of the project have expanded a bit. We’re still aiming to understand how different corals have evolved to structure their microbial communities, but, as the new name implies, we are now also looking at how these communities differ geographically in corals around the world. We know that corals that are related to each other can inhabit vastly different environments, so describing the microbes they associate with in only a subset of those environments wouldn’t get the whole picture. For example, corals that look like this:

can be found in places as wide ranging as the cold, nutrient-rich, upwelling-fueled waters of the Eastern Pacific, the calm waters of the Society Islands in the South Pacific (where I took this photo), and the crystal clear, positively balmy waters of the Red Sea, from whence I am writing this post. Most taxonomists place individuals from either end of their range into the same species, but at some point that is an arbitrary decision. There are clear physiological differences within coral species that are correlated with geography. If you transplanted a colony of Pocillopora damicornis from Panama to Saudi Arabia, the elevated water temperatures would almost certainly cause it to bleach and die. Why? Dunno. Some researchers, such as the Meyer lab at OSU, are trying to figure that out by looking at genetic differences in the corals. Others suggest that corals can gradually acclimate to such extremes in temperature. We think those hypotheses are part of the story, but that the microbes that live with corals might tell another important part. After all, the interactions with microbes through disease and bleaching are the most common causes of coral death. If we compare the differences in microbes across a host species’ range of environments to the differences explainable by the coral’s evolutionary history, we might be able to explain why some corals are more tolerant of variation in the environment than others.

As I procrastinate on my mountains of queued labwork, I am happily organizing and editing my photos from the field. We have photographed each sampled coral colony, hoping to use the collection as a backup for the metadata that we collected simultaneously. The photo at the top of the page depicts the last coral we sampled on this trip – one that had me pumping my fists underwater in excitement! It’s not a particularly rare species, but Jesse and I had a long wish list, a short span of time, and a limited number of reefs to explore. In order to describe the broad levels of variation in the coral microbiome, we are trying to sample at least two species from each coral family we come across, in each location. After we visit a number of reefs around the world, we hope to have enough replication within each family to describe how they differ from one another. As our tanks of air slowly got lower on gas, we still hadn’t found a symbiont-bearing representative of the Dendrophylliidae, though we knew it was around here somewhere! Just as I had given up on it, I spotted that yellow rock. And to be honest, the excitement I felt at that moment is the real reason that I do what I do.