On some moonless nights, enormous patches of the Northwest Indian Ocean and seas around Indonesia begin to glow. This event has been witnessed by hundreds of sailors, but only one research vessel has ever, by pure chance, come across this bioluminescent phenomenon, known as milky seas. Thanks to that vessel, samples showed that the source of the light was a bacteria called V. harveyi, which had colonized a microalgae called Phaocystis. But that was back in 1988, and researchers have yet to be in the right place and the right time to catch one of these events again.

Both the bacteria and algae are common to those waters, so it’s not clear what triggers these rare events. To help understand why milky seas form, researchers have gotten much better at spotting these swaths of bioluminescence from the skies. With the help of satellites, Stephen Miller, a professor of atmospheric science, has been collecting both images and eyewitness accounts of milky seas for nearly 20 years. Thanks to improvements in the imaging capabilities over the past decades, Miller published a compilation last year of probable milky seas in the time frame of 2012 to 2021, including one occurrence south of Java, Indonesia, in summer 2019. //

Although milky seas can be massive—greater than 100,000 square kilometers in the case of the 2019 sighting—the intensity of this bioluminescence is still relatively faint. By comparison, the better-known sea sparkle from marine plankton (dinoflagellates) is 10 times stronger—and even that can be hard to spot. //

“When waking up at 2200 the sea was white. There is no moon, the sea is apparently full of ? plankton ? but the bow wave is black! It gives the impression of sailing on snow!” the Ganesha crew wrote in their logs.

This glow was continuous as far as they could see, and they also compared the effect to glow-in-the-dark stickers. When they collected some of the water in a bucket they found that the light extinguished when stirred, which is the opposite of dinoflagellate behavior.

“I was surprised by their description of the pinpoints of light that vanished upon stirring and the sense that the glow was coming from depth,” writes Miller. “The disappearing glow may be due to bacterial communities being broken up that made their individual glow less apparent than when concentrated on a particle, or a change in the water that shut off that glow… not sure!” //

“I would also like to point out that while we look in collective awe at the incredible photos from James Webb Space Telescope coming from the edges of our universe, there still somehow remain these fascinating mysteries down below, waiting to be discovered, appreciated, and learned about,” adds Miller.

When I was a little boy, my parents and I took the ocean ferry out to Nantucket one blustery summer day. My father had me make a handwritten note with my address. We put it in an empty wine bottle, corked it good and tight, and walked back to the stern where the propellers were churning the saltwater with thunder.

A 1966 study by the U.S. Navy noted that "The passage of large-amplitude internal waves could make submarine depth control difficult, particularly when the submarine is running quietly at low speed." The report, titled Internal Waves: Their Influence Upon Naval Operations, added that such waves "could initiate uncontrollable sinking of a submarine."

In World War II, submariners avoided the Strait of Gibraltar partly because they were aware of its reputation for propagating unusual undersea waves that were considered hazardous, David Farmer, a physical oceanographer at the University of Rhode Island, told USA Today in 2014.

At the height of the Cold War in 1984, a Soviet submarine that was apparently running beneath a tanker to mask its exit from the Strait suddenly smashed into the tanker's hull, causing damage to both vessels and forcing the submarine to surface. The collision is thought to have been caused by an internal wave that unexpectedly thrust the submarine toward the surface.

The waves "are generated over steep topography due to the surface tides," he tells NPR. "In the South China Sea, internal wave amplitudes can be about 100 meters (330 feet)."

Fertilizer runoff is likely fueling an explosion of seaweed in the Atlantic.

There’s a mass of seaweed in the Atlantic Ocean that last year, at its peak, was so large it stretched all the way from the Gulf of Mexico to West Africa. It’s the biggest bloom of seaweed ever recorded, according to a new paper published in Science. And it’s likely another example of how human activity is radically changing the surface of the planet.