Inactive hydrothermal vent microbial communities are important contributors to deep ocean primary productivity.

Area of Science:

• Deep-sea biology
• Geochemistry
• Microbial ecology

Background:

• Active hydrothermal vents support high productivity but eventually cease activity, leaving mineral deposits.
• Microbial activity rates on these inactive deposits are poorly understood.

Purpose of the Study:

• To investigate primary production on inactive hydrothermal deposits.
• To quantify the contribution of these sites to deep-ocean organic carbon production.

Main Methods:

• Measured 14C-bicarbonate incorporation to assess carbon fixation rates.
• Utilized single-cell uptake experiments and nanoscale secondary ion mass spectrometry (nanoSIMS).
• Conducted metagenomic and lipidomic surveys of microbial communities.

Main Results:

• Microbial communities on inactive deposits fix inorganic carbon at rates comparable to active vents.
• Chemoautotrophs represent a substantial portion (>30%) of active cells.
• Alphaproteobacteria and Gammaproteobacteria dominate, utilizing the Calvin-Benson-Bassham pathway.

Conclusions:

• Inactive hydrothermal deposits are significant sites of microbial activity.
• These deposits contribute to new organic carbon production in the deep sea.
• Chemoautotrophic microbial communities play a key role in carbon cycling at these locations.