High pCO2-induced exopolysaccharide-rich ballasted aggregates of planktonic cyanobacteria could explain Paleoproterozoic carbon burial

Nina A. Kamennaya, Marcin Zemla, Laura Mahoney, Liang Chen, Elizabeth Holman, Hoi Ying Holman, Manfred Auer, Caroline M. Ajo-Franklin, Christer Jansson

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

The contribution of planktonic cyanobacteria to burial of organic carbon in deep-sea sediments before the emergence of eukaryotic predators ~1.5 Ga has been considered negligible owing to the slow sinking speed of their small cells. However, global, highly positive excursion in carbon isotope values of inorganic carbonates ~2.22–2.06 Ga implies massive organic matter burial that had to be linked to oceanic cyanobacteria. Here to elucidate that link, we experiment with unicellular planktonic cyanobacteria acclimated to high partial CO2 pressure (pCO2) representative of the early Paleoproterozoic. We find that high pCO2 boosts generation of acidic extracellular polysaccharides (EPS) that adsorb Ca and Mg cations, support mineralization, and aggregate cells to form ballasted particles. The down flux of such self-assembled cyanobacterial aggregates would decouple the oxygenic photosynthesis from oxidative respiration at the ocean scale, drive export of organic matter from surface to deep ocean and sustain oxygenation of the planetary surface.

Original languageEnglish
Article number2116
JournalNature Communications
Volume9
Issue number1
DOIs
StatePublished - 1 Dec 2018
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry (all)
  • Biochemistry, Genetics and Molecular Biology (all)
  • Physics and Astronomy (all)

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