Bioluminescence – Nature’s Magical Lights

When I conduct my weekly night-snorkelling trips in the house reef, one of the highlights for my guests and I is always the sheer abundance of bioluminescent plankton organisms. We switch our torches off for a minute and stir the water up with our fins and hands, making crustaceans, polychaetes and jellies produce tiny bright lights. The atmosphere becomes magical when you see all these stars below you in the water as well as the stars up in the sky. But even if you don’t go into the reef at night, you can witness bioluminescence. During many nights of the year, bright-blue spots can be seen on Maldivian beaches, lighting up when the waves hit the sand and fading after a few seconds. Some evenings are so spectacular (as was the case last night) that entire beach sections are aglow with millions of tiny lights that seem to brighten up even more when touched or walked on. Last night was truly a special night that was appreciated by everyone: All resort guests returning from our weekly General Manager’s cocktail party on the sandbank were playing with the glowing beach sand, taking lots of photos and generally being all in wonder of such rarely seen beauty. Luckily the moon was in its full glory too, so that its light helped expose the photos I took and contribute to the overall atmosphere.

The bioluminescence around Soneva Fushi is mainly caused by microscopic benthic crustaceans, Ostracoda. They are about 1 mm in length, flattened from side to side and protected by a bivalve-like calcareous shell. At night, the ostracods rise from the sandy sea floor, where they spend the day, and feed on planktonic algae. When the animals get disturbed, either through predators or the movement of waves, a light-emitting substance is ejected that deters predators. It is this light that makes our beaches glow. I collected Ostracoda samples today and looked at them under my microscope. They were all drawn to the light and seemed sensitive to the slightest changes in light direction. I also wanted to see whether they were possibly all getting ready to mate and therefore occurred in such large numbers last night. However, the animals contained eggs of different developmental stages, even fully developed embryos, so that I had to discard my little hypothesis of a mass mating event... If only I had more time to investigate all these exciting events happening around Soneva Fushi throughout the year, I am sure we could stumble on some interesting explanations of our observations! It is for these kind of experiences that I love being a marine biologist on this island!