June 10, 2015

Chagos' Candy Colored Coral

On a recent snorkel here in Salomon Atoll we were treated to a long and leisurely swim with a turtle as well as the puppy-like attention of a very young and curious black tipped reef shark. As Maia swam and dove with the turtle, which circled back again and again rather than speeding off, we were also mesmerized by all the colour around us: fluorescent lime green, pink, purple and blue corals sprouted like wildflowers across the seafloor, each one a more extraordinary shade than the last.  

We've seen the aftermath of coral bleaching many times in our travels—it appears as stark white coral that has crumbled or has algae and seaweed covering it. But this short-lived first step of bleaching, which occurs after the coral animals expel the algal cells (zooxanthellae) which usually live in their tissues—is less well known. To understand what was happening I contacted a researcher through the BIOT. Jon Slayer from the Living Ocean Foundation explained that in healthy coral the algae are pigmented from the chlorophyll they use for photosynthesis, giving most coral a dark green, brown, beige or yellow colour. But when the algae are expelled, the coral's white limestone skeleton becomes visible. And for a brief time a coral with fluorescent pigments may appear lime green, purple, pink, red or blue.

Researchers were in the BIOT in March and April of this year. During their first voyage in April, the reports were extremely positive—there was no sign of the bleaching event that is sweeping through the Pacific and water temperatures were a healthy 25-29° C. By late April, sea temperatures had risen to 30-31° C (which is enough to stress the coral) and a warming (and bleaching) event was in full swing.

It's a helpless feeling to swim in one of the most pristine places in the world and know it's in peril. While we can't change the current situation, we have found a small way to help the researchers: Our group of boats has volunteered to help catalogue the progression of bleaching for the researchers—to be their eyes, when they can't be here. It's a small thing but it's a great excuse to get in the water each day and play with turtles and sharks and revel in all the beauty and mystery of our planet.

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