Elevated pCO2 enhances bacterioplankton removal of organic carbon

PLoS One. 2017 Mar 3;12(3):e0173145. doi: 10.1371/journal.pone.0173145. eCollection 2017.

Abstract

Factors that affect the removal of organic carbon by heterotrophic bacterioplankton can impact the rate and magnitude of organic carbon loss in the ocean through the conversion of a portion of consumed organic carbon to CO2. Through enhanced rates of consumption, surface bacterioplankton communities can also reduce the amount of dissolved organic carbon (DOC) available for export from the surface ocean. The present study investigated the direct effects of elevated pCO2 on bacterioplankton removal of several forms of DOC ranging from glucose to complex phytoplankton exudate and lysate, and naturally occurring DOC. Elevated pCO2 (1000-1500 ppm) enhanced both the rate and magnitude of organic carbon removal by bacterioplankton communities compared to low (pre-industrial and ambient) pCO2 (250 -~400 ppm). The increased removal was largely due to enhanced respiration, rather than enhanced production of bacterioplankton biomass. The results suggest that elevated pCO2 can increase DOC consumption and decrease bacterioplankton growth efficiency, ultimately decreasing the amount of DOC available for vertical export and increasing the production of CO2 in the surface ocean.

MeSH terms

  • Carbon / metabolism*
  • Carbon Dioxide / metabolism*
  • Cyanobacteria / metabolism
  • Ecosystem*
  • Environmental Monitoring
  • Humans
  • Oceans and Seas
  • Phytoplankton / metabolism*
  • Seawater / microbiology
  • Water Microbiology

Substances

  • Carbon Dioxide
  • Carbon

Grants and funding

NSF OCE 1041038 - awarded to Uta Passow, Craig A Carlson, and Mark A Brzezinski NSF OCE 12-36905 - awarded to the Moorea Coral Reef LTER Simons Foundation International - awarded to Craig A Carlson NSF OCE 1156626 - awarded to Rachel A Parsons and Jennifer N Trapani NSF OCE 1232779 - awarded to the Santa Barbara Channel LTER. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.