For some coral, home isn’t where the heart is—it’s where the sounds are. A recent study showed that one type of coral prefers to settle on reefs that sound healthy—even if they’re not.

Young corals, known as larvae, float or swim through the water for a while. When they find a good spot, they drop to the bottom and grab hold. They use several cues to find the best locations, including the lighting and chemistry. And according to the study, one of those cues might be sounds.

Biologists recorded the sounds of both healthy and un-healthy reefs in the U.S. Virgin Islands. Healthy reefs are noisy. They feature the clicks of snapping shrimp and the grunts and groans of fish. Unhealthy reefs are much quieter.

The scientists placed small groups of larvae in special containers on three reefs. One reef was healthy, with a good amount of coral. The others had less coral and much more algae, which can kill a reef.

Researchers played the sounds of a healthy reef to the larvae on one of the damaged reefs. On the other two reefs, the larvae had only the natural sound of the environment.

On average, the larvae that were played the healthy sounds were 1.7 times more likely to settle on the reef than those at the other reefs—even the healthy one. So playing a nice lullaby into damaged reefs might lure new generations of coral in the years ahead.

Our thanks to T. Aran Mooney of the Woods Hole Oceanographic Institution for the reef sounds.

The oceans are losing their memory. That could make it harder to forecast everything from monsoons to blizzards.

Ocean “memory” is maintained in the top layer, called the mixed layer. Winds push warm surface water downward, where it mixes with water at greater depths. This layer is typically about 150 feet thick. And overall, it maintains a fairly constant temperature. When the temperature changes as the result of some major event, it can take 10 to 20 years for the change to dissipate. In other words, the ocean maintains the “memory” of what happened to it for that long.

As the air warms up, though, ocean memory may be changing. Researchers recently simulated changing ocean conditions with computer models. Their work suggested the memory span may be getting shorter, mainly because water at the surface is getting warmer and less dense, so it doesn’t sink as easily. As a result, the mixed layer gets thinner, so its temperature can change more quickly. The quicker the change, the shorter the memory. As one researcher described it, the ocean develops amnesia.

Ocean memory is an important factor in forecasting conditions in both the oceans and the atmosphere. Scientists use it to predict monsoon seasons, heatwaves, exceptionally wet summers and cold winters, and other major climate events. A shorter ocean memory could cut months from the lead time of these forecasts—making it harder to remember whether to take an umbrella or sunscreen on your next outing.

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.