Science and the Sea podcast

For a tiny marine worm found in the Bay of Naples and elsewhere, life ends in a frenzy. The worms lose a lot of their internal organs, their eyes get bigger, and they rise to the surface. There, as they paddle furiously, they release sperm and eggs, creating the next generation. And it’s all triggered by moonlight.

The worms are one of more than 10,000 species of marine bristle worm. They’re only about an inch long. Each body segment has a pair of paddle-like structures tipped with bristles. The worms live at the bottom of warm, shallow waters around the world. And they’re considered “living fossils”—they haven’t changed much in tens of millions of years.

The bristle worms are especially sensitive to changing light levels. They build tubes on the ocean floor. When a shadow passes across them, they pull back into the tubes to elude possible predators. And their end-of-life ballet is triggered by moonlight.

The body changes begin around the time of “new” Moon, when there’s little or no moonlight. The worms then rise to the surface not long after the full Moon.

Scientists recently studied how that happens. They found that some proteins react differently with different light levels. Under bright sunlight, they stay apart, in separate units. But under dimmer conditions, the units stick together. That allows the worms to not only distinguish between day and night, but between different phases of the Moon—a light-activated “trigger” for a big change.

Conditions in the Arctic Ocean may be about to switch gears. That could mean that Arctic waters would become more like those in the North Atlantic—a process known as “atlantification.” As a result, sea ice would disappear a lot faster than it has in recent years.

The rate of sea-ice loss peaked in 2007. The total amount of ice is still going down, but much more slowly than it was before. In December of 2023, in fact, the sea ice increased at a higher rate than in all but two other months in the past 45 years.

A recent study said the slowdown in ice loss may be a result of the Arctic dipole—a pattern in the way air circulates over the far north. Today, there’s high pressure over the Canadian arctic, and low pressure over Siberia.

That pattern reduces the flow of warmer water from the North Atlantic Ocean into the Arctic Ocean. There’s a thicker layer of colder, fresher water at the top of the Arctic. That keeps the ice from vanishing as fast as expected based on the higher air temperatures produced by our warming climate.

Scientists looked at decades of observations made from ships, airplanes, and satellites. They found that the dipole might be about to flip over—from “positive” to “negative.” If that happens, the changing circulation in the atmosphere would allow more water to flow in from the Atlantic. That would warm the upper layers of the Arctic, causing sea ice to disappear much faster—boosting the “atlantification” of the Arctic.

Some tiny sea snails may look like angels, but they act more like little devils. They rip their favorite prey from their shells. And the prey just happens to be a relative.

Sea angels are found around the world, from the arctic to the tropical waters near the equator. Most range from the surface to depths of a couple of thousand feet, although some have been seen more than a mile down.

Sea angels are born with shells, but they lose them as they become adults. They’re no more than a couple of inches long, and they have streamlined bodies. They’re mostly transparent, which helps them hide from predators. The Antarctic sea angel has extra protection: it produces a nasty chemical that keeps most predators away.

What gives sea angels their “angelic” appearance is a pair of wings. They’re adapted from the muscular foot of their land-based cousins. The creatures move through the water by flapping those wings. They can move twice as fast as their prey.

Their favorite treat is another sea snail—the sea butterfly. Some angels lie in wait, while others are more active hunters. They grab their prey with small tentacles that extend from the head. Hooks allow them to pull the butterfly from its shell in as little as two minutes.

Sea angels and their prey are jeopardized by climate change, which makes the oceans more acidic—a hazard for any creature that produces a shell. That’s an extra challenge for these angelic little devils flapping through the world’s oceans.

Now playing in the southwestern Pacific Ocean: Sharkcano—an underwater volcano filled with sharks.

Officially, the volcano is Kavachi. It’s named for a fire god of a nearby culture. Its base is about three-quarters of a mile deep.

Kavachi is one of the most active volcanoes on the planet—there’s almost always a little something going on. Its first recorded eruption came in 1939. Since then, it’s erupted at least eight more times, including a long-lasting one from late 2022 into ’23.

The eruptions produce big underwater plumes of gas, rock, and ash. Currents carry the plumes miles away, staining the ocean surface. Some eruptions send debris into the sky. They can even build islands up to about half a mile long. The islands don’t last long, though—wind and waves quickly wear them down.

An expedition in 2015 arrived during one of Kavachi’s rare quiet times. That allowed scientists to float above the volcano’s summit, where they could sample the water and rocks, map the crater’s contours, and look for life. And they found a lot of it. Big patches of microscopic organisms that feed on sulfur and carbon dioxide coated the volcano’s flanks. And snapper and other fish swam through the crater.

That included silky sharks and scalloped hammerhead sharks—inspiring Kavachi’s nickname. The sharks probably swim in and out over the crater’s rim. But they seemed to be doing well in the Kavachi’s hot, murky, acidic waters—living inside the Sharkcano.

The “beards” of marine mussels aren’t just a fashion statement. They anchor the mussels to the sea floor, attach to each other to form large “beds,” and hold out potential invaders. They’re also playing a role in materials research—scientists study the beards to learn how to make water-proof glue for many applications.

The beards consist of a bundle of about 20 to 60 threads known as a byssus. The threads radiate outward from the mussel’s “foot.” Each thread is tipped with a biological superglue—a combination of proteins from the mussel and metals from the water.

Mussels use the byssus to anchor themselves to the bottom, where they wait for tiny prey organisms to float through their shells. The threads are strong but flexible, so they allow the mussels to sway with the tides. The glue never dissolves in the water. The mussels can use the threads to move along the bottom; they anchor one thread, then “reel” it in to shift position.

When the mussels are threatened, though, they let go in a hurry. Tiny hairlike structures on the bottom of the foot beat rapidly, detaching the byssus from the mussel’s body. The mussel grows a new one in just a few hours.

Scientists are studying the byssus to help develop ways to attach sensors or implants to the human body. They’re also looking for ways to overcome the glue to prevent mussels—especially freshwater species—from fouling underwater outlets or other structures—getting free of some “sticky” threads.