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Diatoms Si uptake capacity drives carbon export in coastal upwelling systems

Publication . Abrantes, Fatima; Cermeno, Pedro; Lopes, C.; Romero, Oscar; Matos, Lelia; Van Iperen, Jolanda; Rufino, Marta; Magalhaes, Vitor

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.

2016Journal article

Open Access

Data report: IODP Expedition 339 Site U1391: an improved splice and preliminary age model on the basis of XRF data

Publication . Abrantes, Fatima; Santos, C.; Ventura, C.; Voelker, Antje; Röhl, U.; Stow, Dorrik A. V.; Hernandez-Molina, F. Javier; Alvarez Zarikian, Carlos A.; Expedition 339 Scientists

With the objective to reconstruct past primary production on the southwest Portuguese margin at orbital and millennial timescales through the Pleistocene, we chose to compare two sites recovered during Expedition 339 at similar latitude but different distances to the coast (Sites U1385 and U1391). Site U1385 has a well-established chronology, but for Site U1391 no isotope data are yet available. In order to develop a correct chronology without isotope data, we performed XRF analysis of cores from Holes U1391A and U1391B between 76.51 and 205.77 mbsf. With these data, in particular using log(Ca/Ti) and log(Ca/Fe), it was possible to enhance the Site U1391 splice and to establish an age model based on the correlation to the well-defined and robust Site U1385 age model.

2017Book part

Open Access