This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Antarctic krill are tiny shrimp-like creatures that were previously thought to mostly inhabit the upper layer of the Southern Ocean. Although they had occasionally been observed at deeper levels, they were never seen near deep-sea hydrothermal vents until 2024, when a group of oceanographers observed them there for the first time.
The team's new study, published in Communications Biology, describes the discovery and why the team thinks pregnant krill may actually be spending a lot of time near hydrothermal vents. Antarctic krill serve as a major food source for whales, seals, penguins, seabirds and many other animals in the Southern Ocean. The predators that don't eat krill likely eat animals that do.
Krill also play a role in nutrient recycling and carbon sequestration in the ocean. By eating algae, they convert nutrients into usable forms of nutrition for other species and turn carbon into sinking fecal pellets that pull carbon down from the surface into the deep ocean. The researchers say Antarctic krill likely have the highest cumulative biomass of any wild animal species on Earth, at around half a billion tons.
Around a third of this biomass is located in the area between the northern Antarctic Peninsula and the Scotia Sea, one of the fastest-warming areas on the planet. In addition to the threat of climate change, Antarctic krill fisheries are also putting their populations at risk. The study authors write, "Consequently, Antarctic krill populations are under increasing pressure, and there is mounting recognition at an international level of the need to conserve critical Antarctic krill habitat to ensure their populations continue to thrive into the future.
However, we still lack fundamental knowledge on what constitutes critical habitat for key parts of the Antarctic krill life cycle—particularly for reproductive females." During surveys of active hydrothermal vent fields, Hook Ridge and Quest Caldera, the researchers discovered and collected several Antarctic krill with a remotely operated vehicle. They compared vent-site krill with krill from a non-vent seafloor site and analyzed their gut microbes, stable chemical signatures and trace metals in their tissues. Of the four captured krill from Hook Ridge, all were mature, egg-carrying females that had recently mated.
Video footage at Hook Ridge showed several additional gravid female Antarctic krill swimming near the vent structures, while no male krill were observed during the nearly nine-hour period. At the Quest Caldera site, many pregnant Antarctic krill were also observed on video during an approximately 21-hour period, along with dense swarms at the active venting site. A comparative group was taken at a non-vent site in the Antarctic Sound and consisted of a mix of juveniles, males and females.
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