Spatio-temporal variability in benthic silica cycling in two macrotidal estuaries: Causes and consequences for local to global studies

Type Article
Date 2013-03
Language English
Author(s) Raimonet Melanie1, Ragueneau Olivier1, Andrieux Loyer Francoise2, Philippon Xavier2, Kerouel Roger2, Le Goff Manon1, Memery Laurent1
Affiliation(s) 1 : Inst Univ Europeen Mer, UMR CNRS UBO IRD Ifremer 6539, Lab Sci Environm Marin LEMAR, Plouzane, France.
2 : IFREMER, DYNECO Pelagos, Plouzane, France.
Source Estuarine Coastal And Shelf Science (0272-7714) (Academic Press Ltd- Elsevier Science Ltd), 2013-03 , Vol. 119 , P. 31-43
DOI 10.1016/j.ecss.2012.12.008
WOS© Times Cited 11
Note MOITEM I, Février 2009 (11/02/2009 au 16/02/2009), Côtes de la Manche MOITEM II, Mai 2009 (3/05/2009 au 8/05/2009), Côtes de la Manche MOITEM III, Juillet 2009 (23/07/2009 au 27/07/2009), Côtes de la Manche MOITEM IV, Octobre 2009 (28/10/2009 au 01/11/2005), Côtes de la Manche
Keyword(s) heterogeneity, season, silicate, sediment, land-sea interface, upscaling
Abstract The high heterogeneity of silica cycling in coastal margins and the lack of silica data (compared to nitrogen and phosphorus) prevent the estimation of global silica retention in estuaries. In this study, the spatial and temporal variability of porewater silicic acid (Si(OH)4) profiles e that integrate benthic transport and reaction processes e was investigated at different spatial (metre, longitudinal and crosssection, intra-estuary) and temporal (tidal, seasonal) scales in two macrotidal estuaries, very close geographically but essentially differing in their shape. Studying the spatial and temporal variability of Si(OH)4 concentrations in porewaters provided evidence for the importance of transport processes, e.g. bio-irrigation, tidal pumping, resuspension and any combination of these processes, in affecting Si(OH)4 concentrations and fluxes and therefore temporary or permanent retention along the landeocean continuum. We confirm that aSiO2 (amorphous silicate) transported by rivers and estuaries clearly needs to be better characterized as it provides an important source of reactive aSiO2 to sediments. This study allows us to: (1) interrogate spatial and temporal scales, although both are most often in complete interaction; (2) design the most appropriate sampling schemes to be representative of any given system and to extrapolate at the scale of the whole estuary; (3) quantify uncertainty associated to the estimations of Si(OH)4 stocks and fluxes in this type of ecosystem, essential for budget calculations. We showed that two adjacent small macrotidal estuaries, may exhibit different behaviours regarding Si retention. Temporary retention has been observed in the meanders of the Aulne Estuary and not along the more linear Elorn Estuary, demonstrating the importance of the morphology and hydrodynamic components of the estuarine filter. Research is needed in other systems and climatic zones, but our study suggests that the typology should not only account for the different types of landeocean continuum (fjord, delta, mangrove.), but also incorporate the physical or biological attributes of the estuarine filter.
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Raimonet Melanie, Ragueneau Olivier, Andrieux Loyer Francoise, Philippon Xavier, Kerouel Roger, Le Goff Manon, Memery Laurent (2013). Spatio-temporal variability in benthic silica cycling in two macrotidal estuaries: Causes and consequences for local to global studies. Estuarine Coastal And Shelf Science, 119, 31-43. Publisher's official version : https://doi.org/10.1016/j.ecss.2012.12.008 , Open Access version : https://archimer.ifremer.fr/doc/00124/23529/