Antarctic krill filmed feeding at deep-sea hydrothermal vents

BRANSFIELD STRAIT, Antarctica — In the traditional hierarchy of marine biology, the life cycle of Antarctic krill (Euphausia superba) was thought to be entirely dictated by the sun. Forming massive swarms in the upper 300 meters of the Southern Ocean, these tiny, shrimp-like crustaceans graze on sun-lit photosynthetic phytoplankton, acting as the primary biological engine that feeds Earth's largest populations of whales, seals, and penguins.

However, a landmark discovery published in Communications Biology by National Geographic Explorer Dr. Kim Bernard and her research team has completely upended that ecological baseline. Conducted during the National Geographic and Rolex Perpetual Planet Southern Ocean Expedition in collaboration with the Schmidt Ocean Institute, oceanographers captured unprecedented remotely operated vehicle footage of Antarctic krill actively living, feeding, and congregating around toxic, boiling deep-sea hydrothermal vents more than 3,000 feet below the surface. HoneyNewspaper's science desk has been tracking deep-sea ecosystem discoveries that challenge traditional assumptions about marine food webs.

Even more surprising was the demographic makeup of the abyssal swarms: every single krill sampled at the hydrothermal vent sites was a gravid female carrying dense clusters of eggs. The discovery was verified across two separate Antarctic vent sites, Hook Ridge in the Bransfield Strait and the Quest Caldera in the Scotia Arc, proving the behavior is a widespread ecological strategy rather than an isolated anomaly. The findings were published in Communications Biology.

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Hydrothermal vents are mineral-rich, super-heated underwater hot springs that spew toxic heavy metals and sulfur compounds into pitch-black waters. Normally, life around these vents relies strictly on chemosynthesis, bacteria that convert vent chemicals into energy without sunlight. Using ROV suction samplers to collect specimens directly from the vent plumes, Dr. Bernard's team performed isotopic, gut-microbial, and trace-metal analyses on the captured females.

The results confirmed two key motivations driving these deep dives. First, the krill's digestive tracts contained clear chemical signatures of chemosynthetic bacteria, proving they are actively eating vent microbes to sustain their high metabolic energy demands while developing eggs. Second, tissue samples revealed elevated levels of manganese, a crucial trace mineral required for crustacean embryo development that is extraordinarily rare in surface waters of the Southern Ocean. The gravid females are essentially utilizing hydrothermal vents as mineral-supplementation stations before releasing their eggs.

The animals and wildlife beat has reported on how krill form the foundation of the Southern Ocean food web, with whales, seals, and penguins all dependent on their seasonal abundance. This discovery adds a previously unknown dimension to krill ecology that has direct implications for managing the commercial krill fishery.

Conservation Implications for a Threatened Fishery

This discovery comes at a critical juncture for the Southern Ocean. Antarctic krill represent one of the largest single-species biomasses on Earth, yet they face severe pressures from rapid climate warming and an expanding industrial commercial fishery. The regional krill fishery was forced to shut down early for two consecutive years after rapidly reaching its regulatory catch triggers.

Until now, international conservation frameworks and Marine Protected Area proposals focused almost exclusively on protecting the top 300 meters of the ocean water column. Demonstrating that breeding female krill rely on deep seafloor vents means marine managers must expand environmental protections downward, safeguarding deep-sea benthic habitats from potential seabed disruptions to protect the foundation of the Antarctic food web. The environment desk has covered how Southern Ocean marine protected area negotiations are complicated by competing scientific and commercial interests, and this discovery adds a new data point that strengthens the case for deep-sea habitat protection. Follow ongoing coverage of marine biology, deep-sea ecosystems, and polar science on our science desk.