Lights in the Bay
Henry S. Parker
In the darkness of December, tidewater Maryland begins to glow. All along the Bay—in Severna Park and Solomon’s, Havre de Grace and Hoopersville, Chestertown and Chesapeake City—the shoreline shimmers with holiday lights. In Annapolis two public, light-spangled spectacles draw thousands of sightseers every year.
The first, Lights on the Bay (Nov. 19 to Jan. 2), presents more than 60 illuminated exhibits along a scenic drive at Sandy Point State Park. The other, Eastport Yacht Club’s annual Parade of Lights on Dec. 11, features a slowly-circling procession of local boats bedecked in kaleidoscopes of imaginative, nautical-themed and sometimes hilarious displays.
These are impressive shows, sure to kindle the holiday spirit of even the most Scrooge-like among us. But few are aware that, year-round, beneath the Bay’s waters, there lurks an even more impressive display of lights: bioluminescence.
Bioluminescence is natural light produced by living organisms. We’re all familiar with a terrestrial version: fireflies. But the phenomenon is rare on land, largely limited to lightning bugs, glow worms and a few species of fungi. In contrast, it is common in the ocean.
Have you have spent time on the Bay at night? If so, you have likely seen the sparkle of a boat’s wake or the pinpoint pricks of light in the swirl of a dipped oar. The physical disturbance has stirred up living creatures. Some respond by undergoing a chemical reaction catalyzed by an enzyme. The enzyme, luciferase, combines with a pigment molecule, luciferin, releasing light energy (but not heat) in the process.
The shallow waters of Chesapeake Bay harbor many bioluminescent life forms including various microbes, plankton and jellyfish. The tiniest are some species of bacteria, notably the human pathogen, Vibrio cholerae, which, regrettably can be abundant in local waters. Other common light-producers are Ceratium and Noctiluca (translation: “night light”), types of microscopic one-celled motile algae known as dinoflagellates. Larger light-emitting Bay denizens include soup bowl-sized moon jellies which produce a bluish light when agitated. The smaller, translucent and gelatinous sea walnut, a type of comb jelly (not a true jellyfish), is also bioluminescent. Sea walnuts often cluster together. When disturbed, the mass emits a luminous green glow. No, it’s not brighter near Calvert Cliffs.
The submarine light show in Chesapeake Bay can be impressive, especially in late summer. But it pales in comparison with what goes on in the deep sea.
Even in the clearest ocean waters, the sun’s rays penetrate only a few hundred feet below the surface. This means that 90 percent of the oceans’ volume is perpetually dark—dark, that is, except for biological light. And there is plenty of biological light: Scientists estimate that four-fifths of deep sea creatures—notably shrimps, fish, jellyfish, marine worms and squid—may be luminescent. Their light is concentrated in special organs, called photophores, which are arrayed in species-specific patterns. In the vast expanse of the dark deep sea, this may help individuals to locate and recognize potential mates and avoid incompatible—or dangerous—liaisons.
Photophores may also function in predator-prey interactions. The bizarre-looking deep sea angler fish sports an elongated dorsal fin, complete with light organs, just above its gaping jaws. When illuminated, the fin acts as a lure for unwary victims. Alternatively, bioluminescence may be a defense mechanism. The bright flash given off by disturbed sea creatures may startle or confuse predators.
Bottom line: bioluminescence has adaptive value in the eternal whirl of the survival of the fittest. But when you go down to the sea at night and watch a light show beneath the waves, you need not think of nature red in tooth and claw. Instead focus on the beauty of a timeless natural spectacle. It rivals the holiday lights any time.
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