March 20th – When you go to the beach or bay at night and see tiny sparkles of light coming from the water, it isn’t your imagination. It’s Noctiluca! From the Latin for “night light,” Noctiluca are also known as Sea Sparkle. These tiny dinoflagellates float beneath the surface of the ocean by the millions. When they are disturbed, they glow and produce bright flashes of light. This glow is called “bioluminescence,” and in the ocean it is usually greenish or blue, as these colors travel well through the water. You can encourage Noctiluca to glow by whirling your hands and feet in the water. On a night dive, the fins of a SCUBA diver can leave a trail of fireworks behind them! The wake of a boat can often be seen glowing as well. (It is thought that ancient Polynesian mariners used a signal from deep bioluminescing plankton to locate and navigate around islands.) But why do Noctiluca sparkle? No one knows for sure. It probably has to do with hunting or communication. One idea is that it startles predators. Or perhaps it helps attract larger predators who can turn Noctiluca’s own into prey. Or maybe the lights are used to bewitch Noctiluca’s own quarry. Or maybe it’s just a fun way to say good night. #365DaysOfMicrorscopy

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