Otto the octopus didn’t appreciate the spotlight shining on his laboratory tank at night. So he turned it off. In fact, he turned off the lights in the whole lab.

Octopuses are smart and curious. They use tools and learn from watching other octopuses. They can solve mazes, open the lids of glass jars, and build dens.

In the lab, they learn to tell people apart. They’ve been known to take a disliking to some of the lab workers, squirting jets of water at them when they walk by. And they can show a clear preference for the people who feed them.

Octopuses also play. In one study, scientists put some small, sealed plastic bottles in octopus tanks. Some of the critters fired jets of water at the bottles, bouncing them off the walls. Others fired a bottle toward the tank’s inlet valve, so the bottle came back to them—like octopus ping-pong.

And that brings us back to Otto. Scientists in Germany were studying the behavior of Otto and several others. Otto was the most active. He damaged the glass walls of his tank by throwing rocks at them, and he sometimes rearranged the stuff in the tank.

A 2,000-watt spotlight shined on the tank at night. But several times, the light shorted out—and so did the rest of the lab. Scientists then spent the night in the lab to figure out what was happening. Otto was climbing to the rim of the tank and squirting water at the light. That turned out the lights—perhaps allowing Otto to get a good night’s sleep.

A rare species of sponge found in the Red Sea and Indian Ocean has a rare distinction: It has levels of a metal that are thousands of times higher than ever seen in any other organism. And most of that metal is stored away by a type of bacteria that lives inside the sponge.

Sponges are filter feeders—they draw in water, filter out food and other solid bits, then shoot the water and solid particles back into the sea. Some contaminants can lodge inside them. Some studies have found high levels of arsenic, barium, and other toxic substances.

A more recent study looked at the species called Theonella conica. It’s found down the eastern coast of Africa. Up to 40 percent of its body weight consists of bacteria and other microscopic organisms, many of which have a symbiotic relationship with the sponge.

Over two decades, researchers collected specimens from Zanzibar, off the southeastern African coast, and the Gulf of Aqaba, at the northern tip of the Red Sea.

When they analyzed the sponges, the scientists found extremely high levels of molybdenum. The metal is important for the metabolism of people and other animals, but only at low levels. At high levels it’s toxic. So the metal may help protect the sponges from predators.

The element was concentrated in one of the species of bacteria inside the sponge. It changes the material into a harmless mineral, which is flushed back into the water—keeping the sponge safe from both predators and the toxic element.

The journey around Cape Horn, at the southern tip of South America, is one of the most treacherous in the world. The cape has claimed hundreds of ships and thousands of sailors. Not many commercial vessels make the journey today. But for sail-powered yachts, rounding the cape is a big attraction—like climbing Mount Everest.

Cape Horn is named for the home town of the Dutch navigator who described it, in 1616. It’s a small island that features a cliff a quarter of a mile high.

The cape is where the Atlantic and Pacific oceans meet. The confluence generates strong currents. Those currents are magnified by the contours of the ocean floor, which features many sunken islands.

The region is in the “Furious Fifties”—latitudes of more than 50 degrees south. Strong winds blow from west to east. Those are funneled by the mountains of South America and Antarctica. That creates a wind tunnel effect, so winds almost always blow at gale force. And they frequently top hurricane force, battering any ships that challenge the passage.

In addition, icebergs are common features, and storms bring heavy rain, hail, sleet, and snow. That all combines to make a journey around Cape Horn especially challenging.

The opening of the Panama Canal, in 1914, provided a safe shortcut between the east and west coasts of the Americas. But big tankers, naval vessels, cruise ships, and private yachts still round the cape—one of the most dangerous ocean voyages in the world.

The coconut crab is the 800-pound gorilla of many tropical beaches. Not only is it the biggest and strongest crab on land, it’ll eat just about anything—animal, vegetable, or even mineral.

Coconut crabs are found in tropical environments in the Indian and southwestern Pacific oceans. They hatch in the sea, where they float around for a few weeks. They then move ashore, where they live in the discarded shells of other creatures. The crabs lose the shells when they become adults. They stay close to the beach, but they don’t go back in the water; they have lungs instead of gills, so they drown if they stay underwater for long.

An adult coconut crab has a leg span of about three feet, and can weigh up to nine pounds. It has powerful claws that can crack open a coconut and scoop out the meat. It can even climb a tree to knock a coconut to the ground.

The crabs also have been seen to climb trees to attack seabirds. Most of their diet consists of fruits, seeds, and dead animals. They eat abandoned shells for their calcium. But they sometimes grab birds, rats, or even other crabs. And they steal many human artifacts, from pots and pans to firearms, so they’re also known as robber crabs.

Coconut crabs have been wiped out in some regions. They’re hunted for their meat, crowded out by human development, and damaged by higher sea level and warmer oceans. Some areas offer legal protection—a helping hand—or claw—for these giants of the beach.

It looks like something a six-year-old dreamed up in art class—the body of a fish, the “wings” of a bird, the legs of a crab, and even the taste buds of a human tongue. Throw in some loud croaks and grunts, and you’ve got one of the ocean’s many oddities: the sea robin.

The fish is found in warm waters around the globe—usually in shallow water with a sandy or rocky bottom. A typical adult is a foot or more long, although some species can reach twice that size. The fish have tapered bodies, and heavy skulls that help them poke around the bottom for food—shrimp, clams, crabs, and small fish.

When a sea robin swims, the fins on the sides of its body fan out like the wings of a bird—hence the name. As the fish matures, the “rays” at the front of these fins change. They form small “legs” that the fish uses to walk along the bottom.

But the legs are for more than just getting around. The fish uses them to feel out prey. And at least one species may use them to “taste” prey before they ever see it.

In a recent lab study, biologists buried some of the sea robin’s favorite foods below the sand and watched them feel it out. They then buried some of the chemicals produced by the prey. And they found that one species quickly dug up those goodies as well. The legs of those fish were coated with tiny sensory organs that are a bit like the taste buds on your tongue. They allow the sea robin to “taste” its food well before it even swallows it.

A steep change in the slope of a riverbed can create rapids—regions where the water is especially fast and choppy—and dangerous. The same thing applies to rivers in the sky. Steep changes in altitude, temperature, or pressure can concentrate the water, creating rapids. They can cause downpours that are especially fast and heavy—and dangerous. That appears to be the case for recent springtime flooding in the Middle East.

Atmospheric rivers form when water evaporates from the ocean. As it rises, it’s caught in a jet stream, forming a tight, high-speed river. The average one delivers as much water per minute as the mouth of the Mississippi River.

When an atmospheric river crosses land, it can produce rain and snow. That can be helpful. But it also can be deadly, producing flooding, mudslides, and other dangers.

A recent study blamed deadly flooding in the Middle East in April 2023 on such a river, but one with rapids—waves with much higher concentrations of water. They dumped as much rain as some regions see in an entire year. Similar flooding in 2024 also might have been caused by rapids. The rapids were powered by evaporation from the Atlantic Ocean and the Arabian and Mediterranean seas.

Our warming climate is increasing the rate of evaporation. It’s also changing circulation patterns over the Atlantic. So the deserts of the Middle East could see more flooding in the years ahead—perhaps powered by rivers and rapids high in the sky.

The great white shark has the most fearsome reputation of all sharks. But it might not be the biggest of the predator sharks. That honor might go to the Pacific sleeper shark. The biggest one ever seen appeared to be about 23 feet long—longer than the biggest great white.

The Pacific sleeper is found mainly in cold waters around the rim of the northern Pacific Ocean. But some have been seen in warmer waters close to the equator.

The shark got its name because it was thought to spend most of its time near the bottom, waiting for prey to swim by—a “sleepy” sort of behavior. But at least one study found otherwise. The sharks were found to move up and down through the water column, from the bottom to near the surface. And some covered as much as three or four miles a day.

Pacific sleepers will eat just about anything. They prefer fish that dwell on the bottom, along with giant octopus. But their stomach contents also show other types of fish, snails, sea lions, and other prey. They might have hunted down some of them, and gobbled the already dead remains of others.

The shark hasn’t been studied that much. The largest one ever caught was about 14 feet long and weighed half a ton. But video cameras caught one that was estimated at 23 feet.

Pacific sleepers probably grow slowly and have a low reproduction rate. So they could be threatened by overfishing, mostly as bycatch—draining the population of what might be the largest of all predator sharks.

Currents at the bottom of the ocean can be just as fickle as wind currents at the surface. They can turn, speed up or slow down, and even reverse course. And they can change in just days or even hours.

That’s the conclusion of the most detailed study of sea-floor currents to date. Researchers anchored 34 instrument packages across a thousand-square-mile region off the coast of Mozambique, at the southeastern corner of Africa. The instruments monitored the currents for four years.

The study took place on the continental slope, at depths of up to a mile and a half. The slope is steep, and sharp canyons notch into it. Sediments tumble down the slope and through the canyons.

At the bottom of the slope, the currents generally flow from south to north. And in the canyons, they generally flow downhill. Speeds range from about a half to one-and-a-half miles per hour.

But researchers found a lot of variation. The speed changes, and so does the direction. Currents can even reverse direction—even in the canyons, where they sometimes flow uphill. Some of the changes are related to the tides or to passing storms or eddies. And others are related to the seasons, so they play out over days or weeks.

The researchers say a better understanding of sea-floor currents can tell them more about where ocean sediments come from. That can help them better understand changes in climate, the sources of pollution, and more—swirling along at the bottom of the sea.

In the spring of 1956, a doctor in the Japanese village of Minamata reported an outbreak of a troubling new disease. It was seen mainly among children, and it affected the central nervous system. The disease quickly spread, with hundreds of cases reported, then thousands. It took years for scientists to work out the cause: poisoning from industrial pollution in Minamata Bay—the first known case of a disease caused by polluted seawater.

A chemical factory was pumping huge amounts of wastewater into the bay. The water was laced with mercury. Some of it was methylmercury—an especially nasty form.

Microscopic organisms gobbled the stuff up, then were eaten by larger organisms. The amount of mercury built up to higher and higher levels with each link in the food chain. So the fish and shellfish eaten by people were filled with it. That triggered Minamata disease. Symptoms included numbness, problems with vision and hearing, trouble walking, and tremors. The disease killed hundreds, and may have afflicted millions. And its effects are still being felt.

The company dredged the bay to remove contaminated sediments. And the nations of the world crafted a treaty to reduce the amount of methylmercury in the environment. It calls for less mercury in products and manufacturing, fewer emissions of it from coal-fired power plants, and better storage and disposal.

Even so, mercury and other chemicals still cause problems as they work their way up the marine food chain.

The parrotfish is like a house cleaner who does a great job of keeping things tidy, but sometimes breaks a glass. You want to keep them around, but you just wish they’d be a little less destructive.

For the parrotfish, the “houses” are coral reefs. They clean tiny organisms off the coral, keeping the coral healthy. But they also chip off pieces of the coral. If they chip away too much, they can damage the coral.

Parrotfish have strong teeth. They grind up the coral they chip off, then poop it out as grains that can wash up on the beach as white sand.

The scraping can scar the hard coral—the “skeleton” created by the living organisms inside, known as polyps. In many cases, the coral heals as new polyps move in. But in others, the coral can collapse. And if too many corals are destroyed, an entire reef can suffer.

Researchers spent a decade studying the coral-parrotfish relationship in four regions of the Caribbean Sea. They looked at individual corals, complete reefs, and wider areas that encompass many reefs. They also studied the parrotfish populations.

They found that more parrotfish generally meant more damage to the corals—but not always. Parrotfish prefer some species of corals over others. So in regions where those species weren’t as common—or where there was less variety of coral species—the damage was less severe.

The results may help managers control the parrotfish catch—perhaps improving the health of coral reefs across the Caribbean.