Biogeochemistry

Deep-sea carbon fix

Glob. Biogeochem. Cycles http://doi.org/ks3 (2013)

Deep-sea microbial communities convert inorganic carbon into organic matter, fuelling benthic ecosystems, but the magnitude of this conversion — and the identity of the microbes responsible — remains uncertain. Measurements in marine sediments suggest that primitive, single-celled organisms known as archaea contribute significantly to this carbon fixation at the sea floor.

Antonio Dell'Anno of the Università Politecnica delle Marche, Italy, and colleagues monitored the rates of carbon fixation (the transformation of inorganic carbon into organic matter) in marine sediments collected from the Iberian margin in the Mediterranean Sea and northeastern Atlantic Ocean. On average, inorganic carbon fixation accounted for 19% of the biomass produced by seafloor microbes, with the rest presumably derived from sinking organic matter. The findings suggest that inorganic carbon fixation helps to sustain deep-sea food webs.

An analysis of the microbial community composition in the sediments revealed a positive association between archaeal abundance and rates of inorganic carbon fixation, suggesting that archaea are key contributors to carbon cycling in the deep sea. Indeed, the researchers' selective inhibition of archaeal metabolism resulted in the complete inhibition of inorganic carbon fixation.

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Armstrong, A. Deep-sea carbon fix. Nature Geosci 6, 246 (2013). https://doi.org/10.1038/ngeo1795

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