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Exploring a Biofluorescent Reef

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Explorers gear up for a night dive on the House Reef at Angel Island, Indonesia. 37.8600° N, 122.4300° W.

A setting sun darkens the surrounding islands of Komodo National Park, Indonesia, and while your typical diver is turning in for the night with a cold Bintang, we gear up. Explorers Club Flag Expedition #216 was not like the others. Fueled by our curiosity for the mysterious biological phenomena where blue light is absorbed by certain marine creatures and transformed into vivid shades of green, yellow, and red, this expedition blended cutting edge cinematography and science to capture some of the first-ever time lapse recordings of fluorescent anemones, corals, and bony fishes.

Put simply, our purpose was to film a fluorescent event on a coral reef. Unlike bioluminescence, a phenomenon whereby organisms produce their own light, when they want to, by way of a chemical reaction, biofluorescence is a passive process that animals can’t turn off and on and biofluorescence is not visible with the naked eye. It requires a blue-light and yellow filter over the eye, and it is best illuminated at night.

That means that with the right gear, we had a good chance of encountering a biofluorescent event. Oh and gear we had: GoPro cameras, retrofitted with an extended battery life and yellow lens, blue lighting systems, weights, tripods, and a homemade buoy made from plastic bag strips and sandals.  The team had their hands full. Descending onto the reef, we place yellow filters over our goggles and turn on the blue lights. Suddenly everything is black, except for a select brain coral head and the occasional anemone which stand out in neon. 

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Retrofitted GoPro Camera and Blue Light in action, documenting a 4-6 hour time-lapse of a fluorescing anemone. PC: Rick Elkus

Of the many species we observed during our 3 night dives, our favorite observation was of a giant anemone. The fleshy stalk that supports the tentacles glowed a deep red, while the tentacles glowed a neon green. The central gut, located under the tentacle, was an even more intense green, while the tips of the tentacles, in contrast, were dramatically dimmer, and like the body, may even be glowing slightly red.

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Anemone and clownfish, captured with fluorescence gear, revealing a fluorescing neon green anemone and a non-fluorescing clownfish. PC: Rick Elkus

While observing this anemone, we also met its resident clownfish. Like many other clownfish-anemone symbiotic relationships, this anemone protects the clownfish from predators, and provides food through the scraps left from the anemone’s meals and the occasional dead anemone tentacles. In return, the clownfish defends the anemone from its predators, and parasites. In the time lapse footage we were able to observe how this clownfish interacted with the host anemone. In white light, the white strips on the body of the clownfish seem clearly intended to blend with the tentacles of the anemone. However, our fluorescence gear revealed that there appears to be no fluorescence on the clownfish. In fact, the complete lack of fluorescence on the clownfish makes it quite a target in contrast to the intensely glowing center of the anemone, essentially creating a shadow as it swims past. To avoid the threat of predation, the clownfish has a habit of diving deep into the tentacles, thus obscuring itself and any shadow it might have otherwise cast. This habit, observed frequently during the day, was reenforced by our fluorescent observation as an essential mechanism for self-preservation for the clownfish.

Little is known about what role the phenomenon of biofluorescence plays in nature. It is hypothesized that many creatures use it for communication, predation and spawning events. During this Explorers Club Flag Expedition #216 we briefly observed fluorescent behaviors and we hope that these observations will add to the collective knowledge on the behavioral aspects of biofluorescence.

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Expedition Team, pictured left to right: Shaggy Voegele, Kathryn Nemmers, Patty Elkus, Rick Elkus, Evva Fenison, Amber Jackson, Kristina Elkus, Ken Brennan, Jessica Elkus, and Lindsey Guendling.