Gaze out across the ocean on a calm, sunny day, and you might be forgiven for believing the sea to be a tranquil place. But as every snorkeler or diver knows, the shallow coastal waters are abuzz with life and drama.
I made this recording in about 5 meters (15 feet) of water, at the end of a concrete pier some 50 meters (150 feet) from shore near Anse Mamin on the west coast of St Lucia in the Caribbean Sea. During a brief lull in boat traffic (sadly, a rare event in popular tropical tourist destinations like the Caribbean) the natural undersea sounds burst forth.
Behind the delicious slurp of gentle currents washing past the hydrophones and concrete pilings of the pier, you can hear the pops, snaps, grunts, whines, and sputterings from a host of small creatures prowling and grazing on the coral reefs nearby. I’m sure a marine biologist could name them all, but for now let’s just listen with eyes closed, and soak up this lively oceanic ambience.
- I couldn’t help but dig a little deeper into the cause of that persistent loud crackling and popping. It turns out that this is the sound of snapping shrimp (genus Alpheus), a ubiquitous inhabitant of shallow tropical seas. This creature, which grows no larger than your little finger, has the remarkable ability to stun its prey with sound, in a way that modern science has only recently begun to understand: it snaps shut its claw so fast that it actually creates a hole — a steam bubble — in the water itself. The bubble immediately collapses, releasing a flash of light and a violent pulse of sound into the surrounding water. Woe to any little coral fish that drifts within range of this deadly sonic blast! (“How Snapping Shrimp Snap: Through Cavitating Bubbles”, by Michel Versluis, Barbara Schmitz, Anna von der Heydt, and Detlef Lohse (Science, 22 September 2000; Vol. 289. no. 5487, pp. 2114-2117).)