Oceans

Ancient oxygen-making microbes may have oxygenated large swaths of Earth’s seafloor hundreds of millions of years before the element filled the atmosphere.

Geochemical analysis of sediments deposited roughly 2.6 billion years ago reveals that pulses of oxygen may have swept through large regions of the ocean, researchers report April 26 in Nature Geoscience. The findings suggest that cyanobacteria, the microorganisms responsible for oxygenating Earth’s atmosphere, were more widespread at the time than previously believed.

This shows that not only had cyanobacteria already evolved, but they were around in vast numbers and had even oxygenated the seafloor, says geochemist Kurt Konhauser of the University of Alberta in Edmonton, Canada, who was not involved in the study. And that, he says, means aerobic organisms might have evolved on the seabed long before oxygen permeated the sky. More

McKenzie Prillaman is a science and health journalist based in Washington, DC. She holds a bachelor’s degree in neuroscience from the University of Virginia and a master’s degree in science communication from the University of California, Santa Cruz. She was the spring 2023 intern at Science News. More

Off the coast of the Solomon Islands lurks a centuries-old being that is so immense, it can be seen from space.

Discovered in October by the National Geographic Society’s Pristine Seas team, it is the world’s largest standalone coral. Coming in at roughly 34 meters wide, 32 meters long and 6 meters tall, the behemoth coral is longer than the average blue whale. It also dwarfs the world’s next largest-known coral, a 22-meter-wide coral in American Samoa known as Big Momma. More

It’s one of the most massive migrations on Earth: a huge biomass of tiny plankton that travel from deep in the sea toward the surface. Yet not all of those organisms have limbs to propel themselves upward. So how some of them manage to undergo such a long journey has been a mystery.

Now, a team of researchers has shown that one species of phytoplankton has an ingenious solution: swelling to six times its original size. The process reduces its density and allows it to float upward like a helium balloon, bioengineer Manu Prakash and his colleagues at Stanford University report October 17 in Current Biology. More

As dust from the Sahara blows thousands of kilometers across the Atlantic Ocean, it becomes progressively more nutritious for marine microbes, a new study suggests.

Chemical reactions in the atmosphere chew on iron minerals in the dust, making them more water soluble and creating a crucial nutrient source for the iron-starved seas, researchers report September 20 in Frontiers in Marine Science.

Dust clouds settling on the Atlantic can spawn phytoplankton blooms that support marine ecosystems, says Timothy Lyons, a biogeochemist at the University of California, Riverside. “Iron is incredibly important for life,” he says. Phytoplankton require it to convert carbon dioxide into sugars during photosynthesis. More

The ocean’s circulatory system may not be doing as poorly as previously thought.

A vital ocean artery known as the Florida Current, a bellwether for the ocean’s ability to regulate Earth’s climate, has seemingly been weakening for decades. But that recent decline might not be quite as severe as suspected. The current has actually remained stable over recent decades, researchers report September 5 in Nature Communications.

A previously reported decline in the flow had prompted speculations that a major system of ocean currents — known for regulating Earth’s climate — may have weakened recently due to human-caused climate change. Some researchers have suggested that the larger system, known as the Atlantic Meridional Overturning Circulation, or AMOC, could collapse sometime this century, dramatically cooling the northern hemisphere and raising the sea level along some Atlantic coastlines by up to 70 centimeters. More

Abby Wallace is the digital engagement producer at Science News. She has an undergraduate degree in biology from George Washington University in Washington, D.C., and a master’s degree in journalism from the University of Maryland — College Park. More

In an unexpected twist, metal-rich nodules found on the seafloor are generating oxygen, new research suggests. This meager but steady supply of the vital gas may help support seafloor ecosystems in areas currently targeted for deep-sea mining, scientists say.

Scientists have long presumed that much of the dissolved oxygen in the deep sea was transported there from surface waters. It can be generated at the surface by plant life via photosynthesis or diffuse from the atmosphere as a result of wave action, says Andrew Sweetman, a deep-sea ecologist at the Scottish Association for Marine Science in Oban. More