Effects of increased pCO2 and temperature on the North Atlantic spring bloom. I. The phytoplankton community and biogeochemical response

• Published in: Marine Ecology Progress Series
• Main Authors: Feng, Y., Hare, C.E., Leblanc, Karine, Rose, J.M., Zhang, Y., Ditullio, G.R., Lee, P.A., Wilhelm, S.W., Rowe, J.M., Sun, J., Nemcek, N., Gueguen, C., Passow, Uta, Benner, I., Brown, C., Hutchins, D. A.
• Other Authors: College of Marine Studies (CMS), University of Delaware Newark, Department of Biological Sciences Los Angeles, University of Southern California (USC), Laboratoire d'océanographie et de biogéochimie (LOB), Université de la Méditerranée - Aix-Marseille 2-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Woods Hole Oceanographic Institution (WHOI), Hollings Marine Laboratory, College of Charleston, Department of microbiology, The University of Tennessee Knoxville, CAS Key Laboratory of Marine Ecology and Environmental Science (KLMEES), CAS Institute of Oceanology (IOCAS), Chinese Academy of Sciences Beijing (CAS)-Chinese Academy of Sciences Beijing (CAS), Department of Earth and Ocean Sciences Vancouver (EOS), University of British Columbia (UBC), Department of Chemistry, Trent University, Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), Earth Science System Interdisciplinary Center College Park (ESSIC), College of Computer, Mathematical, and Natural Sciences College Park, University of Maryland College Park, University of Maryland System-University of Maryland System-University of Maryland College Park, University of Maryland System-University of Maryland System, College of Marine Studies
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2009
• Subjects: [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; North Atlantic
• Online Access: https://hal.archives-ouvertes.fr/hal-00700400; https://hal.archives-ouvertes.fr/hal-00700400/document; https://hal.archives-ouvertes.fr/hal-00700400/file/m388p013.pdf; https://doi.org/10.3354/meps08133

International audience The North Atlantic spring bloom is one of the largest annual biological events in the ocean, and is characterized by dominance transitions from siliceous (diatoms) to calcareous (coccolithophores) algal groups. To study the effects of future global change on these phytoplankton and the biogeochemical cycles they mediate, a shipboard continuous culture experiment (Ecostat) was conducted in June 2005 during this transition period. Four treatments were examined: (1) 12°C and 390 ppm CO2 (ambient control), (2) 12°C and 690 ppm CO2 (high pCO2), (3) 16°C and 390 ppm CO2 (high temperature), and (4) 16°C and 690 ppm CO2 ('greenhouse'). Nutrient availability in all treatments was designed to reproduce the low silicate conditions typical of this late stage of the bloom. Both elevated pCO2 and temperature resulted in changes in phytoplankton community structure. Increased temperature promoted whole community photosynthesis and particulate organic carbon (POC) production rates per unit chlorophyll a. Despite much higher coccolithophore abundance in the greenhouse treatment, particulate inorganic carbon production (calcification) was significantly decreased by the combination of increased pCO2 and temperature. Our experiments suggest that future trends during the bloom could include greatly reduced export of calcium carbonate relative to POC, thus providing a potential negative feedback to atmospheric CO2 concentration. Other trends with potential climate feedback effects include decreased community biogenic silica to POC ratios at higher temperature. These shipboard experiments suggest the need to examine whether future pCO2 and temperature increases on longer decadal timescales will similarly alter the biological and biogeochemical dynamics of the North Atlantic spring bloom.