Rapid transport and high accumulation of amorphous silica in the Congo deep-sea fan: A preliminary budget

Type Article
Date 2015-01
Language English
Author(s) Raimonet Melanie1, Ragueneau Olivier1, Jacques Vincent1, Corvaisier Rudolph1, Moriceau Brivaela1, Khripounoff AlexisORCID2, Pozzato Lara3, 4, Rabouille Christophe3, 4
Affiliation(s) 1 : Inst Univ European Mer, UMR CNRS UBO IRD IFREMER 6539, Lab Sci Environm Marin, F-29280 Plouzane, France.
2 : IFREMER, Lab Environm Profond, F-29280 Plouzane, France.
3 : UMR CEA CNRS UVSQ, Lab Sci Climat & Environm, F-91190 Gif Sur Yvette, France.
4 : IPSL, F-91190 Gif Sur Yvette, France.
Source Journal Of Marine Systems (0924-7963) (Elsevier Science Bv), 2015-01 , Vol. 141 , P. 71-79
DOI 10.1016/j.jmarsys.2014.07.010
WOS© Times Cited 9
Keyword(s) Continental margin, Land-sea export, Silica cycle, Congo canyon, Deep-sea fan
Abstract Mechanisms controlling the transfer and retention of silicon (Si) along continental margins are poorly understood, but play a major role in the functioning of coastal ecosystems and the oceanic biological pump of carbon. Deep-sea fans are well recognized as carbon sink spots, but we lack knowledge about the importance of the fans in the global Si cycle. Here, we provide a first estimate of the role played by the Congo deep-sea fan, one of the biggest in the world, in the Si cycle. Sediment cores sampled in the deep-sea fan were analyzed to build a Si mass balance. An exceptionally high accumulation rate of amorphous silica aSiO(2) (2.29 +/- 0.58 mol Si m(-2) y(-1)) was found, due to a high sedimentation rate and the presence of aluminum in the sediments. Although favored by bioirrigation, recycling fluxes remained low (0.3 mol Si m(-2) y(-1)) and reconstructed input fluxes could only be explained by lateral inputs coming from the canyon. Preliminary calculations show that the rapid transport of aSiO(2) through the canyon and the excellent preservation efficiency in the sediments imply that 50% of aSiO(2) river inputs from the Congo River accumulate annually in the deep-sea fan. Si:C ratios in deep-sea fan sediments were very low (0.2) and only three times as high as those measured in the river itself, which suggests that material from the river and the continental shelf was delivered directly through the canyon, with very little time for Si and C cycle decoupling to take place.
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Raimonet Melanie, Ragueneau Olivier, Jacques Vincent, Corvaisier Rudolph, Moriceau Brivaela, Khripounoff Alexis, Pozzato Lara, Rabouille Christophe (2015). Rapid transport and high accumulation of amorphous silica in the Congo deep-sea fan: A preliminary budget. Journal Of Marine Systems, 141, 71-79. Publisher's official version : https://doi.org/10.1016/j.jmarsys.2014.07.010 , Open Access version : https://archimer.ifremer.fr/doc/00251/36242/