Appraisal of sedimentary alkenones for the quantitative 4 reconstruction of phytoplankton biomass
Raja, Maria (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Rosell Melé, Antoni (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)

Data:	2021
Resum:	Marine primary productivity is the driving factor in the global marine carbon cycle. Its 31 reconstruction in past climates relies on biogeochemical proxies that are not considered to 32 provide an unequivocal signal. These are often based on the water column flux of biogenic 33 components to sediments (organic carbon, biogenic opal, biomarkers), although other factors 34 than productivity are posited to control the sedimentary contents of the components, and their flux 35 is related to the fraction of export production buried in sediments. Moreover, most flux proxies 36 have not been globally appraised. Here we assess for the first time a proxy to quantify past 37 phytoplankton biomass by correlating the concentration of C37 alkenones in a global suite of 38 core-top sediments with sea-surface chlorophyll-a (SSchla) estimates over the last 20 years. 39 SSchla is the central metric to calculate phytoplankton biomass and is directly related to primary 40 productivity. We show that the global spatial distribution of sedimentary alkenones is primarily 41 correlated to SSchla rather than diagenetic factors such as the oxygen concentration in bottom 42 waters, which challenges previous assumptions on the role of preservation on driving 43 concentrations of sedimentary organic compounds. Moreover, our results suggest that the rate of 44 global carbon export to sediments is not regionally constrained, and that alkenones producers 45 play a dominant role in the global export of carbon buried in the sea-floor. This study shows the 46 potential of using sedimentary alkenones to estimate past phytoplankton biomass, which in turn 47 can be used to infer past primary productivity (PP) in the global ocean.
Ajuts:	European Commission 834934
Nota:	Unidad de excelencia María de Maeztu CEX2019-000940-M
Drets:	Tots els drets reservats.
Llengua:	Anglès
Document:	Article ; recerca ; Versió acceptada per publicar
Matèria:	Primary productivity ; Proxy ; Remote sensing ; Global export and burial ; Marine sediments
Publicat a:	Proceedings of the National Academy of Sciences of the United States of America, Vol. 118, issue 2 (Jan. 2021) , art. e2014787118, ISSN 1091-6490

DOI: 10.1073/pnas.2014787118
PMID: 33380457

Postprint 19 p, 807.8 KB

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