The intra-annual variability of soft-bottom macrobenthos abundance patterns in the North Channel of the Seine estuary

Type Article
Date 2007-09
Language English
Author(s) Desroy Nicolas1, 2, Janson Anne-Laure2, 3, Denis Lionel2, Charrier Gregory4, Lesourd Sandric5, Dauvin Jean-Claude2
Affiliation(s) 1 : IFREMER, Lab Environm & Ressources, F-35400 St Malo, France.
2 : ELICO 28163, FRE, CNRS, Stn Marine Wimereux, F-62930 Wimereux, France.
3 : Univ Rouen, Lab Morphodynam Continentale & Cotiere, UMR 6143, F-76821 Mont St Aignan, France.
4 : Inst Univ Europeen Mer, Lab Ressources Halieut, F-29280 Plouzane, France.
5 : Univ Littoral Cote dOpale, CNRS, UMR 8013, ELICO, F-62930 Wimereux, France.
Source Hydrobiologia (0018-8158) (Springer), 2007-09 , Vol. 588 , N. 1 , P. 173-188
DOI 10.1007/s10750-007-0661-2
WOS© Times Cited 11
Keyword(s) Port 2000, anthropogenic impacts, Abra alba community, sediment, bentho pelagic coupling, Temporal variability
Abstract Temporal and spatial variability of the Abra alba–Pectinaria koreni and Macoma balthica communities was examined in the northern part of the Seine estuary (North Channel) over different space and time scales in order to assess the role that the hydrologic regime and/or anthropogenic influences play in defining benthic communities over time.
Sediment in the North Channel displayed strong spatial and temporal variability, sustained by intense sediment transport episodes. Total macrobenthic abundances ranged widely on the course of the year and there was no evidence of a seasonal signal for the density fluctuations, whatever the spatial scale considered. The bio-sedimentary dynamics can be divided into two periods: the first corresponds to the high flow rate period (January-May) during which fauna is influenced by fine silt/clay deposition, and the second to the low flow rate period (June-December) during which sandy deposits prevail. Despite the absence of significant correlations between sediment composition and abundance, episodes of sediment transport seem to be an important structuring mechanism in the Seine estuary. As a consequence, the faunal composition varied throughout the year. The winter and spring fauna, characterised by species living on muddy fine-sands or muds, were enriched during the summer and autumn by species living in clean fine sand, such as Donax vittatus, Nephtys cirrosa or Spio decoratus, mainly represented by adult individuals. Secondary settlement of drifters may explain the rapid structuration of assemblages a few days after the sandy deposits. Our results suggest the importance of the bentho-pelagic coupling, primarily induced by the sedimentary instability, on the macrobenthic fauna dynamics. The intra-annual variability of assemblages at the mouth of the Seine river and the silted situation of the North Channel might simply be the result of the silting up and alteration of the inner estuary, generated by several decades of man-made modifications and natural processes.
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