Abstract
The long-term resilience of the Southern Ocean ecosystem relies on healthy populations of Antarctic krill, but climate change and increasing fishing pressure are placing this species at risk. Protecting Antarctic krill requires identification of key habitats for critical life history stages. Here, we present multiple lines of evidence that reproductively active female Antarctic krill utilize deep-sea hydrothermal vent habitats. Gravid females collected at Hook Ridge (Bransfield Strait) bore paired spermatophores and exhibited stable isotope signatures, microbial gut communities, and trace-metal profiles consistent with direct consumption of chemosynthetic microbes and prior visitation to vent sites. Complementary ROV footage from Quest Caldera (Scotia Arc) confirms that such vent use is not isolated. Collectively, our findings reveal a previously unrecognized role of vent habitats in the ecology of one of the Southern Ocean's most ecologically critical taxa and highlight the importance of incorporating vent-associated regions into marine protected area planning.