Deep Sea hydrothermal vent habitats support gravid Antarctic krill

Summary

Using a remotely operated vehicle in the Bransfield Strait and the Scotia Arc, researchers found egg-carrying (gravid) female Antarctic krill at deep-sea hydrothermal vents, more than 1,000 metres down at Hook Ridge. Krill collected at the vent had gut bacteria, stable isotope signatures and trace-metal levels that point to feeding on chemosynthetic microbes at the vent, unlike krill sampled at a shallower comparison site in Antarctic Sound. At Quest Caldera, video from a grid survey suggested close to 2,000 gravid females around the vent field, showing that vent use is not a one-off. The authors suggest vents may give spawning females warmth, year-round food and trace metals such as manganese and zinc, which challenges the established view that krill spawn only in the upper water column. They recommend that vent areas in the Bransfield Strait are considered in planning for the proposed Domain 1 marine protected area. The findings rest on a small sample from the vent site (four krill), and how widely krill use vent habitats is still unknown.

Key Findings

Gravid female krill carrying spermatophores were filmed and collected at hydrothermal vents more than 1,000 m deep at Hook Ridge in the Bransfield Strait

Three of the four vent krill had guts where chemosynthetic Campylobacteria made up more than 40% of the bacteria, a clear contrast to krill from Antarctic Sound

Vent krill had a distinct carbon isotope signature (δ13C −24.2‰ vs −21.9‰) and 2 to 540 times higher levels of lead, zinc, cadmium and barium

A video survey at Quest Caldera in the Scotia Arc estimated 1,991 gravid females along a 2.57 km track, so vent use is not limited to one site

The authors suggest vent areas in the Bransfield Strait should be considered in planning for the proposed Domain 1 marine protected area

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.

Published in

Communications Biology, 2026, Vol. 9, Article 1129

2026

Authors

Kim S. Bernard

Angelo F. Bernardino

Kristen N. Buck

Salvatore Caprara

R. Ben Freiberger

Elizabeth Hogan

Rachel L. Kaplan

Aaron Micallef

Laura E. Moore

Sarah Seabrook

Andrew R. Thurber

Institutions

College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA

Departamento de Oceanografia, Universidade Federal do Espirito Santo, Vitoria, Brazil

National Geographic Society, Washington, DC, USA

Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA

Department of Marine Science, University of Otago, Dunedin, Aotearoa, New Zealand

Department of Ecology, Evolution and Marine Biology & Marine Science Institute, University of California, Santa Barbara, CA, USA

Methods

Field

Biological sampling

Genomic sequencing

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