Crystal Blue & Cotton Candy Pink

by Nichole Price, member of the Benthic Team

This carpet of pink crustose coralline algae at Palmyra bodes well for the health of the reef in the future.

It’s day five on Palmyra, one the most beautiful places on earth, and I couldn’t be happier. Today we are diving at my favorite site here, the northwest fore-reef at about 35 ft depth. The water is crystal blue and gin clear, reef fish of every color and size swarm all around us, and the reef floor is covered in cotton candy pink. The source of the pink color has been the focus of my research program on Palmyra for the past two years and today I get to see the first results from my labors!

Palmyra has an extraordinary abundance of reef building species that includes not just the well-known corals but also an important and often underappreciated group—the crustose coralline algae. These pink, rock-like seaweeds are responsible for the vivid colors I see on the reef floor beneath me. This group is unique among the algae in that they make a hard calcareous skeleton, much like corals, yet they get all of their energy from photosynthesis, like kelp and other algae. Their function in the ecosystem is vital for coral reef resilience in times of natural disturbances. These encrusting algae cement the reef framework, thus strengthening it against storm damage. They also produce a chemical signal that encourages baby corals to settle —a first step in rebuilding a depleted coral population following a disturbance. Seeing so many of them here tells me that not only is this reef healthy today, but it will do better than many when challenged by climate change in the future.

Nichole in the blue world above water.

At reefs suffering from lots of local human disturbances (such as overfishing and sedimentation), their crustose coralline algae grow really slowly, even slower than corals. For my research, I’ve been investigating the growth and survival of these encrusting algae at remote locations (like Palmyra) that are free of local disturbances but still confronted by global-scale human impacts (like global warming and ocean acidification). Today I was able to document their unprecedented high growth rates at my favorite site on this beautiful, remote, and relatively untouched atoll! About a year ago, we had deployed instruments at this same site to simultaneously measure and record the seawater chemistry and temperature. Once I download the logged data, we’ll attempt to correlate patterns in these extraordinary growth rates with seasonal temperatures and changing water conditions. I wonder what we’ll find!