Sedimentation of ballasted cells-free EPS in meromictic Fayetteville Green Lake

Nina A. Kamennaya, Ping Hu, Christer Jansson

Research output: Contribution to journalArticlepeer-review

Abstract

Fayetteville Green Lake (FGL) is a recognized, extensively studied present-day model of the stratified Proterozoic ocean. Nonetheless, biomass sedimentation in FGL remains hard to explain: while virtually all sediment pigments belong to photosynthetic sulfur bacteria from a chemocline, the isotopic carbon signature of the bulk organic matter suggests its epilimnetic phytoplankton origin. To explain the epilimnetic origin of sedimented carbon, we studied the dominant Synechococci, isolated from FGL. Here, we present experimental evidence that FGL Synechococci produce copious extracellular polysaccharides (EPS) especially when availability of inorganic carbon (Ci) is high relative to availability of other macronutrients, for example phosphorus. The accumulating EPS become impregnated with calcium, magnesium, and sodium cations and are released to the environment as ballasted cell coverings. Sedimentation of these cell-free EPS can constitute the bulk of pigment-free organic material in FGL sediment. Because increased availability of Ci specifically stimulates production of EPS and the accumulated EPS adsorb cations and become ballasted, we propose the universal role of cyanobacterial EPS in biomass sedimentation in the high-Ci Paleoproterozoic ocean as well as in modern aquatic systems like FGL.

Original languageEnglish
Pages (from-to)80-92
Number of pages13
JournalGeobiology
Volume18
Issue number1
DOIs
StatePublished - 1 Jan 2020
Externally publishedYes

Keywords

  • Paleoproterozoic ocean
  • cyanobacteria
  • extracellular polysaccharides
  • meromictic lake
  • organic carbon

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Environmental Science (all)
  • Earth and Planetary Sciences (all)

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