Experiment, interrupted

The first few days in Palau are always chaotic. You're unpacking, organizing supplies, and setting up the equipment you need. You're reintroducing yourself to some staff members at the research station and picking up right where you left off with others. You're driving like a madwoman around town from this office to that office and begging government officials to sign your permits. It's a lot. 

There was one more thing I wanted to do as soon as possible: check on an experiment. You see, last spring, we started an experiment on delayed metamorphosis - the first of its kind in corals, as far as I know. Corals reproduce via larvae that drift around in the water column. But how long those larvae drift could be important. There are lots of experiments on other invertebrates (tube worms, sea squirts, bryozoans) that show that drifting longer isn't necessarily a good thing. Sure, you can end up farther from home and help your species spread to a new area, but things could go wrong in the meantime. You might use up all your energy and then have a hard time going through metamorphosis. If you use up energy reserves, you might be smaller and therefore more susceptible to predators. On the other hand, if you're growing the whole time, you might get too big to stay afloat. You could be forced to settle in a place that you didn't really want to. Even after you settle, you might find yourself in a strange place where it's hard to make a living. Delayed metamorphosis has myriad effects on juvenile invertebrates. 

For the corals we study, delayed metamorphosis could be a big deal. We've found that corals who live in semi-enclosed lagoons are really good at surviving in high temperatures. We want to find out if those corals' babies (larvae) could drift out of the lagoons, settle on outer reefs, survive, and help the outer reefs become better at surviving heatwaves too. But making it out of a lagoon can take a long time - only a little bit of the water flushes out and gets replaced each day. You might have to drift for weeks on end if you want to escape the lagoon. So how does that long period in the water column affect your ability to survive and grow after you settle? 

One of my experimental tiles, covered in algae.

Last spring, I tried to find out. I took some larvae and let them settle on tiles right away. Then I took other larvae and forced them to delay metamorphosis. I was planning for the delay to be at least a week, but after two days, the larvae started rebelling. Some of them settled on the sides of my plastic containers, and I got scared that I would lose my chance. I was only able to make them delay metamorphosis for two days. We let the larvae settle, put the tiles out on a rack next to PICRC, and then took photos of the tiles two days and a week later so we could track who survived and how much they grew. 

We left the tiles out at the end of our spring trip. I got data after two days and a week, but I wanted to look at impacts over a longer timespan too. I wanted growth and mortality data six months after settlement, and then I wanted to see if delayed metamorphosis had any impact on thermal tolerance by using the surviving corals in a heat stress experiment. 

Unfortunately, I will not get that chance. We checked on the tiles yesterday, and all of them are covered in algae. There is not a single surviving coral anywhere on my experiment. Fail. 

I was pretty disappointed but actually not surprised. We had observed some algae growing on the tiles even before we left Palau last May, and I am far from the first researcher to have a coral project surrender to the relentless pressure of tropical algae. Even though I won't get my six-month timepoint for the experiment, I still have data from the two-day and one-week timepoints. I can see if those data show anything interesting. Frankly, the fact that I was only able to make larvae delay metamorphosis for two days is already an interesting result - maybe they don't actually make it out of the lagoons!

If you're not failing sometimes, you're not pushing the boundaries of science. This is just how it goes. On the plus side, I have one less experiment to worry about this trip! Hopefully our others will succeed.