Copy of the body of the article
The sky was cloudy and moonless, leaving no stars to pass through. Alone at the helm in the middle of the Arabian Sea, somewhere between Oman and India, I couldn’t see anything in the black night like ink, except for the dimly lit compass of our ship rolling on the stand. of the gimbal as we got up and swayed by three-meter seas. . But half an hour after my turn, the candles above me began to glow, as if the moon had risen. But there was no moon, no stars, no other ships. The light, it seemed, came from below and grew in intensity. Soon the whole ocean looked bright green but dull, as if the light shone through a sea of milk.
It was August 2010, and I had been sailing for more than two months, volunteering with the NGO Biosphere Foundation to deliver the Mir, a 35-meter ketch they had recently purchased in Malta, at its port of call. origin in Singapore. . During the trip, I had become accustomed to the usual “shining of the sea” caused by dinoflagellates that ignite when the water stirs, causing the light ribbons to turn red from the bow of the Mir. But that was not it. That was the whole ocean, as far as I could see, bright from a uniform, opaque green. Although the compass was still spinning on its mount, the light in the water created an optical illusion, making the sea look perfectly calm, as if we were gliding through phosphorescent skies instead of rough seas.
I woke up the rest of the crew and for more than four hours we were enveloped in this sea of green light, amazed, with no idea what we were witnessing. Finally, a sharp line appeared in front of us where the bright sea ended and the darkness began. Crossing it, we left behind that numinous ghost world and re-entered a familiar one, though we could still see the green glow of chiffon in our stern for another hour before it disappeared. It wasn’t until we arrived at the port 10 days later that we knew the name of the creepy phenomenon that had surrounded us: a milky sea.
In August 2010, author Sam Keck Scott and his crewmates were sailing in the Arabian Sea when they became some of the few people who witnessed a milky sea. Photo courtesy of Biosphere Foundation
For centuries, sailors have been describing milky seas, rare cases where huge expanses of the ocean are evenly lit at night, sometimes stretching tens of thousands of square miles or more. WE Kingman, captain of the shooting star Clipper, said this when he witnessed one in 1854: “The scene was horribly big; The sea turned to phosphorus, and the sky hung in the dark and the stars faded, seemed to indicate that all nature was preparing for the last great conflagration that we have been taught to believe is to annihilate this material world. .
A milky sea even appeared in Moby-Dick, where Melville describes a sailor navigating a “ghost surrounded by bleached waters” that were “as horrible to him as a real ghost.”
Neither our little crew nor Melville or Kingman knew what made the seas glow. In 2010, our crew had the advantage of living in a much better world of science than in the 1800s, which may explain why Kingman and Melville’s sailor responded with a God-fearing we were amazed, knowing we weren’t. No matter how different this phenomenon may seem, it was clearly from this world.
Bioluminescence, the emission of light by a living organism, is common on our planet, and nowhere more than in the oceans. Bioluminescent fish, tunicates, dinoflagellates, crustaceans, mollusks, jellyfish, and bacteria glow and shine through our seas at night. But lactic seas, despite being so vast, are anything but common, and are believed to be caused by one of the smallest organisms in the ocean.
Every observation of a milky sea throughout history has been a chance encounter, like mine, and only once did it encounter a ship with scientific research capability, when the USS Wilkes sailed a milky sea. for three consecutive nights off the island of Socotra, Yemen, in 1985. On board the Wilkes was the late marine biologist David Lapota, who at the time was working for the Navy studying bioluminescence. Lapota and his team of researchers sampled the water and discovered a profusion of the bioluminescent bacterium Vibrio harveyi, a common and well-dispersed species known for luminescence, attached to pieces of algae, which led them to consider the hypothesis that legions of this bacterium and potentially other bioluminescent. also the bacterial species, are the cause of the lactic seas. This research, conducted almost 40 years ago, is still the only time a milky sea has been studied in the countryside.
There are no existing photos of a milky sea in nature, but this sample of bioluminescent bacteria demonstrates the uniform brightness of the phenomenon on a small scale. Photo courtesy of Steve Miller
Assuming that scientists are right that milky seas are caused by bacteria, one question remains: why? Unlike many organisms that evolved bioluminescence as a means of escaping predation, bioluminescent bacteria want to eat: the inside of a fish’s gut provides a more reliable home than floating freely in the ocean. open. But a lone bacterium is probably too small to attract the attention of a fish on its own, so for its microscopic bioluminescence to be expressed at the macroscale, they need strength in numbers. To work together, each bacterium emits a chemical signal to detect if there are other bacteria nearby, and only once they have recognized a sufficient number do scientists hypothesize that a population of 10 to 100 million bacteria is needed to milliliter of water. they begin to illuminate. This is a process called quorum detection, and may explain why lactic seas are formed.
In emerging areas, such as the northwestern Indian Ocean, where a large amount of decaying organic matter rich in nutrients, such as pieces of decayed crabs or even long-dead whale spots, s ‘pushing to the surface from the depths, bacteria will find much to colonize. When these rich waters become isolated due to currents, or when different bodies of water with different salinities or temperatures meet and form physical fronts, they can avoid mixing, which in turn can lead to a kind of concentrated stew. which scientists have dubbed the “natural flask hypothesis.” In this scenario, by detecting quorum, these bacteria trigger a chemical glow that can become the largest sample of bioluminescence on the planet.
This idea of a natural flask may help to explain why, when our ship first sailed in a milky sea, the light was dim and almost imperceptible, but when we left hours later, we crossed a clear border. On one side of that particular event, bright and non-bright water was mixing, while on the other side, due to some sort of ocean front, a wall-like barrier was maintained between the conditions. specialized – and little understood – that allow milky seas to form and those conditions that do not. This is just one of the many things scientists hope to understand better by studying more of the lactic seas in the field, which, thanks to a new generation of satellite technology, will soon be possible.
Steve Miller, director of the Cooperative Institute for Atmospheric Research, has been part of a small group of scientists leading the effort to demystify the lactic seas for nearly 20 years, looking for them from the most unlikely: Fort Collins, Colorado. He is the first person to discover a milky sea from his office chair.
Miller contacted me shortly after writing a blog post about our experience sailing a milky sea, informing me excitedly that our ship’s crew is among the few people we know today. day they witnessed one. Our brief correspondence made me feel like a minor celebrity.
Miller first became interested in milky seas in 2004 while attending a conference of the American Meteorological Society. There, Miller and his colleagues wondered if it would be possible to observe any kind of marine bioluminescence from space. Any small-scale bioluminescence, such as the brightness of the sea, was supposed to produce a light signal that was too faint to be seen from so far away. But Miller, intrigued by the idea of studying the sea from space, did some research when he returned home and was surprised to discover dozens of surprisingly consistent tales of the so-called lactic seas given by sailors over the centuries. Miller, an atmospheric scientist by training, wondered if he could use historical satellite data to locate one of these events. It didn’t take him long to find what he was looking for: a detailed account of a milky sea seen by the SS Lima crew off the coast of Somalia on January 25, 1995. The story listed the exact coordinates and time. in which it occurred the ship had entered the luminous event. Using the course and speed of the ship’s log, Miller was able to extrapolate Lima’s position at a time when the crew claimed to have come out of the bright waters six hours later. He drew the dots, date, and time on the image and zoomed in on the black and white photo. “It was all black,” he tells me.
Undaunted, Miller decided to shrink the image a little further, searching through the noise of a photograph taken more than half a mile away. Suddenly, a small structure appeared in the center of the computer screen that at first confused it with a fingerprint stain, but when it moved the image, the stain moved with it. He zoomed in and a comma appeared in the waters of the Horn of Africa. When he overlapped the ship’s coordinates again, they aligned with the boundaries of the comma. “That’s when we realized we had something,” he says. The form, larger than the state of Connecticut, had more than 15,000 square miles of bright bacteria.
“I was hooked …