Articles | Volume 13, issue 14
Biogeosciences, 13, 4099–4109, 2016
Biogeosciences, 13, 4099–4109, 2016

Research article 18 Jul 2016

Research article | 18 Jul 2016

Diatoms Si uptake capacity drives carbon export in coastal upwelling systems

Fatima Abrantes1,2, Pedro Cermeno3, Cristina Lopes1,2, Oscar Romero4, Lélia Matos1,4, Jolanda Van Iperen5, Marta Rufino1,2, and Vitor Magalhães1 Fatima Abrantes et al.
  • 1Portuguese Institute for the Ocean and Atmosphere, Rua Alferedo Magalhães Ramalho 6, 1495-006 Lisbon, Portugal
  • 2Centre of Marine Sciences (CCMAR–LA), Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
  • 3Institute of Marine Sciences (ICM-CSIC), Passeio Marítim de la Barceloneta, 37–49, 08003 Barcelona, Spain
  • 4Center for Marine Environmental Sciences University of Bremen (MARUM), Leobener Str., 28359 Bremen, Germany
  • 5Royal Netherlands Institute for Sea Research (NIOZ), Landsdiep 41797 SZ 't Horntje (Texel), the Netherlands

Abstract. Coastal upwelling systems account for approximately half of global ocean primary production and contribute disproportionately to biologically driven carbon sequestration. Diatoms, silica-precipitating microalgae, constitute the dominant phytoplankton in these productive regions, and their abundance and assemblage composition in the sedimentary record is considered one of the best proxies for primary production. The study of the sedimentary diatom abundance (SDA) and total organic carbon content (TOC) in the five most important coastal upwelling systems of the modern ocean (Iberia–Canary, Benguela, Peru–Humboldt, California, and Somalia–Oman) reveals a global-scale positive relationship between diatom production and organic carbon burial. The analysis of SDA in conjunction with environmental variables of coastal upwelling systems such as upwelling strength, satellite-derived net primary production, and surface water nutrient concentrations shows different relations between SDA and primary production on the regional scale. On the global scale, SDA appears modulated by the capacity of diatoms to take up silicic acid, which ultimately sets an upper limit to global export production in these ocean regions.

Short summary
Diatoms are the dominant primary producers of the most productive and best fishing areas of the modern ocean, the coastal upwelling systems. This turns them into important contributors to the biological pump and climate change. To help untangle their response to warming climate, we compare the worldwide diatom sedimentary abundance (SDA) to environmental variables and find that the capacity of diatoms to take up silicic acid sets an upper limit on global export production in these ocean regions.
Final-revised paper