What unknowns remain on the response of the oceans to acidification

  • A variety of natural processes ranging from the response of marine organisms to acidification to the role of sediment in ocean acidification remain to be characterized. This section is not exhaustive and only covers some of the unknowns that have to be investigated.

Role of Sediment in Ocean Acidification

  • The sediment may contribute to ocean acidification by producing CO2 as a result of the decomposition of organic matter by microorganisms
  • Some of the respiration reactions, however, generate alkalinity that may mitigate the release of CO2 to the overlying waters

  • Side chemical reactions also generate acidity or alkalinity, but their impact is poorly quantified. For example, reduced metabolites generated by anaerobic respiration reactions (i.e., DNRA, manganese reduction, iron reduction, and sulfate reduction) diffuse to the sediment-water interface where they are oxidized by dissolved oxygen. These oxidation reactions generate acidity that may contribute to ocean acidification.
  • The precipitation of reduced metabolites (i.e., MnCO3, FeCO3, FeS, and FeS2) may in turn generate alkalinity by preventing reduced metabolites to be oxidized by dissolved oxygen
  • Dissolution of authigenic carbonate minerals near the sediment-water interface may also increase alkalinity
  • Our group studies how sediments generate alkalinity and acidity and attempts to identify the main environmental drivers affecting the balance between acidity and alkalinity generation
  • To realize these objectives, we use autonomous benthic landers that measure the products and reactants of the biological and chemical reactions taking place in sediments. The benthic landers also measure the flux of chemicals at the sediment-water interface that can be used to identify the conditions that either promote or mitigate ocean acidification
Free Autonomous Benthic Lander to simultaneously measure the flux of alkalinity and dissolved inorganic carbon (DIC) across the sediment-water interface and the biogeochemical processes generating acidity and alkalinity in deep-sea sediments
Autonomous Benthic Lander to measure the benthic flux of alkalinity and DIC across the sediment-water interface and the biogeochemical processes responsible for the generation of alkalinity and acidity in continental margin sediments