A couple of years ago, marine biologists bought some giant “seabugs” from fishers in Vietnam. The creatures had been pulled from the mud at the bottom of the South China Sea. They were up to a foot long, weighed a couple of pounds, and had armor plating. The creature had never been cataloged before—it was a new species. Its face resembled the mask of Darth Vader, so the scientists named the seabug after him.

Bathynomus vaderi is one of thousands of marine species discovered in recent years. The list includes fish, corals, crabs, worms, jellies, and others. Unlike the giant seabug, most have been gathered during scientific expeditions.

In early 2024, for example, researchers announced the discovery of more than a hundred new species off the west coast of South America. The scientists had sampled life along an underwater mountain chain, at depths of up to three miles. Each mountain had its own ecosystem, including deep-sea coral reefs and sponge gardens.

Another group found more than five thousand new species across a wide span of the Pacific Ocean, between Hawaii and Mexico. It’s a prime site for possible mining operations, which biologists say could destroy entire species.

Some new species have been found in closets; in 2023, researchers classified some fish that had been captured and preserved 30 years earlier.

An international group hopes to catalog tens of thousands of new species over the coming decade—no matter where they find them.

There’s a big hole in the Indian Ocean. It’s nothing you can actually see. And the ocean itself isn’t especially deep. Instead, it’s a hole in Earth’s gravitational field—the weakest pull across the entire planet.

The “hole” was discovered in 1948. It’s centered about 750 miles off the southwestern coast of India. It covers more than a million square miles—more than a third the area of the Lower 48 states. Gravity there is so weak that surrounding regions of the ocean pull water away from it. As a result, sea level above the hole is about 350 feet lower than the global average.

In 2023, using computer models of the motions of the plates that make up Earth’s crust, scientists suggested the hole may be the remnant of another ocean—the Tethys Ocean. It vanished tens of millions of years ago.

The ocean was wedged between two “super”-continents—slabs that held most of the world’s total land area. But the motions of the plates pulled apart one of the continents. That pushed the plate that held the Tethys Ocean deep into the mantle—the layer below the crust.

The ocean floor reached its deepest point below the surface about 20 million years ago. It pushed away dense blobs of rock, allowing lighter rock to bubble up from below. The lighter rock exerts a weaker pull than the rocks around it.

Scientists still need to confirm that scenario—a possible explanation for a giant “hole” at the bottom of the Indian Ocean.

For an oyster, gender is more than a matter of genetics—it’s also about the environment. Water temperature, salinity, pollution, and other factors determine whether an oyster will be male or female. And a recent study added something new to the list: acidity.

The oceans are becoming more acidic as they absorb carbon dioxide from the air. Over the past couple of centuries, they’ve taken up about a third of all the CO2 added to the atmosphere through the burning of fossil fuels. Today, the concentration of CO2 in the oceans is at its highest in 800,000 years. By the end of the century, it could be at its highest in 20 million years.

The more-acidic waters make it harder for oysters and other creatures to make their shells. And researchers looked at the impact on the sex of oysters. They gathered oysters from the wild and from hatcheries—both in China—and put them in tanks with different levels of acidity. The oysters in the more-acidic water spawned about three times more females than males.

The scientists then placed the new generation in two locations in the wild, with different levels of acidity. Both groups spawned more females than males, but the ratio was higher in the more-acidic waters.

Researchers conducted lab studies to understand how this happens. They found that the higher acidity turned on female-producing genes, and turned off the male-producing genes.

So oysters face one more threat from the world’s changing oceans.