Airai and Ngerur

I could tell as soon as I splashed. Something just didn't look right. The seafloor was white - it wasn't supposed to be white. It was supposed to be red, orange, beige, blue, and green, covered in coral. Instead, I was staring at white calcium carbonate and some stringy turf algae. All. The. Corals. Were. Dead. 

Dead coral and algal turf at Airai. Photo by Kharis Schrage.

This has happened to me before. In 2018, Hanny and I discovered one of our study sites, Mecherchar, was all dead. I'm pretty sure the cause of the mass mortality is heat that causes coral bleaching, but I'm really unsure why it happens all at one site. How hot does it have to get for every single coral in a bay to die? 

This year, the dead site is Airai, our northernmost outer reef site. I need a northern outer reef site for our Porites experiment next year, so I couldn't just skip it. I had to find an alternative. 

Back at the lab, I laid out the map and set about my search. I needed a site that fit very specific criteria. It had to be in the northern part of Palau's Rock Island archipelago. It had to be 6 m deep or less. It had to be exposed to the open ocean, not enclosed in a lagoon. It had to have Porites lobata, and I'd prefer if it had a couple other species too. 

We scoped out a couple alternatives with snorkel surveys, but none of them were great. Then I ran into one of the local researchers from the Palau International Coral Reef Center, Victor. He goes in the field all the time and conducts regular monitoring surveys at sites throughout Palau. If anyone could suggest a site that fit my criteria, it was Victor. 

The healthy reef (and a blue fish!) at Ngerur. Photo by 
Kharis Schrage.

He suggested a site near an island on the western side of Palau, called Ngerur. The next day, I gave the coordinates to our boat operator, and we went to investigate. I found a protected cove on the lee side of the island that was everything I wanted. We had our new study site!

For the record, I don't think Airai is permanently dead. We visited our Mecherchar study site this year, and it's coming back. Three years after the mass mortality, there were plenty of new recruits and even some large mounding and plate corals on the reef. Hanny had also told me before about a large coral near Jarvis Island that she called the "Lazarus coral" because it was completely dead one year and live and thriving a couple years later. It's pretty obvious that we don't understand everything about how corals survive or grow - there is a lot of research yet to be done! I look forward to seeing what corals recruit and re-colonize Airai in a couple years!