Marine researchers exploring a trough off the Antarctic Peninsula in late 2024 discovered Antarctic krill at a deep-sea hydrothermal vent 3,600 feet below the surface. The unexpected finding raises questions about why reproductive females inhabit these extreme, mineral-rich environments.
Antarctic krill are shrimp-like crustaceans widely recognized as the foundation of the South Pole's marine ecosystem. These shrimp-like crustaceans serve as a crucial food source for penguins, seals, and whales. Most of them feed on Antarctic krill,
says Kim Bernard, a biological oceanographer at Oregon State University and a National Geographic explorer. And if they don't, they feed on something else that feeds directly on Antarctic krill. So they are absolutely fundamental to the functioning and health of that ecosystem.
Krill also recycle nutrients that allow tiny algae called phytoplankton to grow. In addition, krill are fished in large numbers to produce aquaculture feed and omega-3 fatty acids as dietary supplements.
An Unexpected Discovery 3,600 Feet Below
While operating a remotely operated vehicle in a trough approximately 3,600 feet below the surface in the Bransfield Strait, scientific teams recorded video footage of a hydrothermal vent. The expedition involved the National Geographic and Rolex Perpetual Planet Southern Ocean Expedition in collaboration with the Schmidt Ocean Institute. One of her colleagues, UCLA benthic ecologist Andrew Thurber, was using a remotely operated vehicle in a trough some 3,600 feet below the surface to study and video record a hydrothermal vent.
While monitoring live screens aboard the research vessel during a little tea break upstairs in the galley, biological oceanographer Kim Bernard spotted a krill near the vent. It's like underwater ballet,
Bernard said, describing the crustacean's distinct backflips and movements.
It just looks like pirouetting. I pretty much threw the tea in the air and ran down to the control room, screaming, 'There's krill, there's krill!'
— Kim Bernard, biological oceanographer at Oregon State University and a National Geographic explorer
Sampling the Extreme Environment
Researchers typically expected Antarctic krill to inhabit upper ocean layers, where they can be found forming swarms and layers at the surface. You can photograph them from airplanes,
according to Bernard. Deeper observations near the seafloor had previously remained sparse and anecdotal.
Hydrothermal vents on the ocean floor are similar to hot springs found on land. Both form where magma under Earth’s crust heats subterranean water to extreme temperatures. That water erupts through the crust, sometimes forcefully, other times in gentle seeps.
Picture extremely hot water coming from deep within the Earth's crust,
says Bernard, and it's bringing with it metals and sulfides and all sorts of other chemicals that form almost like a tower.
Investigating the Drivers of Deep-Sea Behavior
The fluid venting out of the seafloor can reach temperatures of 400° Celsius (750° Fahrenheit). Minerals and chemicals provide a source of energy for deep-sea ecosystems that exist nowhere else on the planet.
Scientists recognize several types of hydrothermal vents, including two well-known types: black smokers and Lost City vents. Black smokers are tall, chimney-like structures that vent high-temperature mineral-rich fluids, measuring around 350° Celsius (660° Fahrenheit) as they exit the chimney. Lost City vents are much cooler, releasing water between 50° and 90° Celsius (122° to 194° Fahrenheit).
Climate Pressures and Future Research Focus
The Southern Ocean represents one of the most rapidly warming areas on the planet, according to experts saying this rich habitat at the bottom of the world is shifting rapidly due to climate change. It's one of the most rapidly warming areas on the planet,
says Bernard, and that's cascading through the food web and affecting the Antarctic krill population.
Now, Bernard and her colleagues report in the journal Communications Biology the discovery of a surprising habitat for the krill — hydrothermal vents, which are basically hot springs on the ocean floor. Characterizing the importance of this habitat, especially for reproductive females, may help inform how to safeguard these crucial crustaceans.