Widespread coral bleaching across the Pacific: can we hear it?

The anomalously warm waters of the Pacific Ocean this fall have led to coral bleaching across the basin. Bleaching - when corals expel their algal symbionts and thereby lose their vivid colors - can result in mortality. One of the reasons the bleaching is so extensive this year is because of the very strong El Nino event that is forecast to occur, which keeps the water temperature high. Bleaching has been widely reported in the mainstream press and is a source of  major concern for the health of coral reefs worldwide.

At the same time, this extent of bleaching allows us to test whether we can detect any changes in the acoustic records that we are currently collecting on reefs. Given that many fish species rely on live coral, and given the high likelihood of mortality at many reefs, we anticipate changes in fish assemblages which could affect what sounds we record.

To test this I am on Maui right now collecting visual survey data from my study reefs. These are critical data points because they will allow me to link any changes that we might see in the acoustic record to changes in the reef species assemblages. I am working with Eden Zang and Marc Lammers of the Oceanwide Science Institute and vessel support is being supplied by Lee James of Ultimate Whale Watch

Yesterday I dived at Molokini Shoal thanks to Hawaii DLNR. Molokini is one of the nicest reefs of my study but bleached coral is everywhere. Mostly it seems to be affecting the Pocillopora and Montipora corals


but it really is widespread. Tomorrow and Monday I will survey the remaining reefs to get a sense of how it is affecting them.

Max Kaplan