Articles | Volume 10, issue 1
Biogeosciences, 10, 315–325, 2013

Special issue: Arctic ocean acidification: pelagic ecosystem and biogeochemical...

Biogeosciences, 10, 315–325, 2013

Research article 23 Jan 2013

Research article | 23 Jan 2013

Effect of increased pCO2 on the planktonic metabolic balance during a mesocosm experiment in an Arctic fjord

T. Tanaka1,2, S. Alliouane1,2, R. G. B. Bellerby3,4,5, J. Czerny6, A. de Kluijver7, U. Riebesell6, K. G. Schulz6, A. Silyakova3,4, and J.-P. Gattuso1,2 T. Tanaka et al.
  • 1INSU-CNRS, Laboratoire d'Océanographie de Villefranche, UMR7093 BP 28, 06234 Villefranche sur Mer cedex, France
  • 2Université Pierre et Marie Curie-Paris 6, Observatoire Océanologie de Villefranche, 06230 Villefranche sur Mer cedex, France
  • 3Uni Bjerknes Centre, Allégaten 55, 5007 Bergen, Norway
  • 4Bjerknes Center for Climate Research, Allégaten 55, 5007 Bergen, Norway
  • 5Geophysical Institute, University of Bergen, Allégaten 70, 5007 Bergen, Norway
  • 6Helmholtz Centre for Ocean Research Kiel (GEOMAR), Düsternbrooker Weg 20, 24105 Kiel, Germany
  • 7Department of Ecosystems Studies, Royal Netherlands Institute of Sea Research (NIOZ), The Netherlands

Abstract. The effect of ocean acidification on the balance between gross community production (GCP) and community respiration (CR) (i.e., net community production, NCP) of plankton communities was investigated in summer 2010 in Kongsfjorden, west of Svalbard. Surface water, which was characterized by low concentrations of dissolved inorganic nutrients and chlorophyll a (a proxy of phytoplankton biomass), was enclosed in nine mesocosms and subjected to eight pCO2 levels (two replicated controls and seven enhanced pCO2 treatments) for one month. Nutrients were added to all mesocosms on day 13 of the experiment, and thereafter increase of chlorophyll a was provoked in all mesocosms. No clear trend in response to increasing pCO2 was found in the daily values of NCP, CR, and GCP. For further analysis, these parameters were cumulated for the following three periods: phase 1 – end of CO2 manipulation until nutrient addition (t4 to t13); phase 2 – nutrient addition until the second chlorophyll a minimum (t14 to t21); phase 3 – the second chlorophyll a minimum until the end of this study (t22 to t28). A significant response was detected as a decrease of NCP with increasing pCO2 during phase 3. CR was relatively stable throughout the experiment in all mesocosms. As a result, the cumulative GCP significantly decreased with increasing pCO2 during phase 3. After the nutrient addition, the ratios of cumulative NCP to cumulative consumption of NO3 and PO4 showed a significant decrease during phase 3 with increasing pCO2. The results suggest that elevated pCO2 influenced cumulative NCP and stoichiometric C and nutrient coupling of the plankton community in a high-latitude fjord only for a limited period. However provided that there were some differences or weak correlations between NCP data based on different methods in the same experiment, this conclusion should be taken with caution.

Final-revised paper