Pic o’ the week: Bioluminescent Beach

Will Ho is among those lucky enough to witness a beach aglow in nature’s own neon. While honeymooning in the Maldives, he saw this beach glittering with … yes, ostracod crustaceans.

Photo copyright Will Ho
By the Dusit Thani resort, Mudhdhoo, Baa Atoll, Maldives. Photo copyright Will Ho.

These entrancing photos have spread across the web, with one scientific misunderstanding. This is not bioluminescent phytoplankton, biology professor Jim Morin of Cornell’s Department of Ecology & Evolutionary Biology, has clarified, but instead is an instance of an amazing mortality event of crustaceans in the Indian Ocean:

“These are tiny crustaceans. They produce these mass mortalities commonly in the Maldives. The species in question is almost certainly Cypridina [=Pyrocypris] dentata, a widespread cypridinid ostracod in the Indian Ocean [and perhaps all the way to the Chinese coast, where they are known as “blue tears”]. There are numerous reports from the Indian coast, especially the west side, and up into the Arabian Sea, in addition to the Laccadives and the Maldives. However, because luminescent bays in the Caribbean and crashing blue waves everywhere in the world are well known, and are usually caused by luminescence from dinoflagellates [which ARE a kind of phytoplankton], there is much confusion about the cause of these “starlit beaches.” But they are clearly NOT dinoflagellates; they are ostracod crustaceans that secrete cypridinid luciferin and luciferase from glands on their upper lips so that the luminescence is external [not intracellular as in dinos]. Furthermore the luminescence is discrete as fairly large spots, not diffuse as with light from millions of dinos. Ostracod light can last many seconds, even minutes, which is not what happens with dinos.”

George Percy noted on Flickr that he remembers these from his childhood in India:

“I am from India … and I used to see them all the time at night on the Marina Beach in Chennai. My friends and I used to scoop them up and hold it in our hands for about 10 seconds and they will lose their luminescence.”