Diatoms Si uptake capacity drives carbon export in coastal upwelling systems
- 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.