Aggregation as a function of P-CO2 and mineral particles

• Published in: Limnology and Oceanography
• Main Authors: Passow, Uta, De La Rocha, Christina L., Fairfield, Caitlin, Schmidt, Katrin
• Other Authors: Marine Science Institute Santa Barbara (MSI), University of California Santa Barbara (UCSB), University of California-University of California, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2014
• Subjects: FECAL PELLETS; RESPIRATION RATES; ACL; TRANSPARENT EXOPOLYMER PARTICLES; ORGANIC-CARBON FLUXES; SINKING VELOCITY; OCEAN ACIDIFICATION; MARINE SNOW; SETTLING VELOCITIES; DIATOM BLOOM; CO2; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Ocean acidification
• Online Access: https://hal.archives-ouvertes.fr/hal-02550589; https://doi.org/10.4319/lo.2014.59.2.0532

International audience A laboratory experiment was designed to investigate the effects of ocean acidification three levels) in the presence or absence of the clay mineral illite (five concentrations) on the coagulation of organic particles. The formation of aggregates. 1 mm from marine detritus and phytoplankton, and their characteristics and sinking velocity, were monitored during the 48 h experiment. Aggregation of particulate organic carbon POC) was independent of both partial pressure of carbon dioxide (P-CO2) and illite addition, implying that the fraction of POC available for export is not affected by either mineral supply or ocean acidification conditions up to ambient + 52.7 Pa P-CO2 (+ 520 ppm). This was true even though the illite appreciably influenced aggregate size, number, and characteristics, including the percentage of transparent exopolymer particles (TEP) incorporated in aggregates. Carbonate chemistry, in the presence of illite, did affect particle formation by clay, carbon, and TEP at the micrometer scale (allocation between dissolved and particulate pools). Our experiment did not resolve processes on this scale well and it remains to be seen if such shifts in the size spectrum of organic carbon and minerals are relevant for the biological pump. High illite content led to small aggregates with a low average sinking velocity. In the absence of biological changes to particle production or loss, coagulation of POC, which is central to the biological pump, is not influenced by ocean acidification or dust input, but sinking velocity and, hence, flux attenuation of POC are likely to be affected by changes in dust input.