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Friday, July 25, 2014         

OCEAN WATCH


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Myriad species light the sea by employing bioluminescence

By Susan Scott

POSTED:



Sailing alone is exhilarating. On the boat my companions are dolphins and seabirds, my entertainment is real-life sea adventure and my destination is a whim. I draw my plans in the sand.

The flip side is that sometimes it's lonely. One evening last week, while anchored in a remote harbor in the northern Sea of Cortez, with no moon, no other boats and a pack of coyotes howling on the beach, I felt distressingly alone. Below deck, as I cooked my dinner for one, I began calculating how long it would take to sail back to the marina, put up the boat and fly home. A splashing commotion was going on outside at the time. Fish jumping, I thought.

Then the sound registered. If those were fish, they were whoppers.

On deck I discovered it was raining pelicans. That's a common event around here when a flock of pelicans gets into a feeding frenzy. But not in the dark. The birds have to see the fish to catch them.

On this inky black night, though, dozens of the albatross-size birds were plunge-diving in their typical cannonball style, each hit causing a burst of fireworks. I looked over the rail. The fish were ablaze! The light-making organisms in this enclosed bay were so dense they illuminated everything that moved.

I felt sorry for the sardine-size fish (talk about shooting fish in a barrel) but applauded the pelicans. This is the species we saw often during the Gulf of Mexico oil spill, the birds bedraggled and helpless with their feathers soaked in oil. Now here were dozens of brown pelicans (their common name as well as their color) in all their glory -- night fishing.

It was too dark to see the birds' takeoffs and dives, but I could hear them: flap-splash-flap-splash. As they work their wings, pelicans also run on the water with their wide webbed feet, getting up speed for takeoff. Two seconds later, crash! The birds were barely airborne before they hit the water in an explosion of sparks, scooping up another glowing meal.

That night anything moving in the water, even the tiniest stir, created a light show. Not only were the thousands of fish schooling around the boat aflame and creating the marine equivalent of contrails, but the boat was aglow, too. The hull, anchor chain, boarding ladder and lines tying the dinghy to the boat all glowed with greenish light accompanied by blue and white flashes. Even my little dinghy bouncing in the slight breeze caused its rubber tubes to sparkle.

In this nutrient-rich coastal bay, the light-makers could have been bacteria, dinoflagellates, jellylike creatures, tiny crustaceans, a combination of those or something else entirely. I can't guess which animals were making the light, because so many species do it.

This is one (of many) of the thought-provoking aspects of bioluminescence. Because the chemicals that create the light are different in different organisms, and the widely varied species use them differently, the ability to make light evolved independently time and again. Whether the flashing helps the creatures avoid predators, find a mate or do something we haven't learned yet, it's obviously worth the energy it takes to turn on the lights.

I don't know what the illuminations did for the creatures making them that night, but they cured my loneliness. After an hour of watching and listening to my fellow mariners fish and flash, I loved being in that remote bay alone. Not only did I get myself there to experience it, I enjoyed having the solitude to truly appreciate it. Once again, sailing alone is exhilarating.

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Susan Scott can be reached at www.susanscott.net.






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