FN Archimer Export Format
PT J
TI Two-dimensional distribution of living benthic foraminifera in anoxic sediment layers of an estuarine mudflat (Loire Estuary, France)
BT 
AF DE CHANVALON, A. Thibault
   METZGER, E.
   MOURET, A.
   CESBRON, F.
   KNOERY, Joel
   ROZUEL, Emmanuelle
   LAUNEAU, P.
   NARDELLI, M. P.
   JORISSEN, F. J.
   GESLIN, E.
AS 1:1,2;2:1;3:1;4:1;5:2;6:2;7:1;8:1;9:1;10:1;
FF 1:;2:;3:;4:;5:PDG-RBE-BE-LBCM;6:PDG-RBE-BE-LBCM;7:;8:;9:;10:;
C1 Univ Nantes, Univ Angers, LPG BIAF, UMR CNRS 6112, F-49045 Angers, France.
   IFREMER, LBCM, F-44300 Nantes, France.
C2 UNIV NANTES, FRANCE
   IFREMER, FRANCE
SI NANTES
SE PDG-RBE-BE-LBCM
IN WOS Ifremer jusqu'en 2018
   copubli-france
   copubli-univ-france
IF 3.7
TC 38
UR https://archimer.ifremer.fr/doc/00277/38786/37335.pdf
LA English
DT Article
AB We present a new rapid and accurate protocol to simultaneously sample benthic living foraminifera in two dimensions in a centimeter scale vertical grid and dissolved iron in high resolution (200 μm). Such an approach appears crucial to study foraminiferal ecology in heterogeneous environments. The foraminiferal faunas of the main intertidal mudflat of the Loire estuary are dominated by Ammonia tepida, which accounts for 92 % of the living assemblage (CTG-labeled). Its vertical distribution shows a first density maximum at the surface, a sharp decrease in the next two centimeter followed by a well defined second maximum between 3 and 8 cm depth. The heterogeneity of A. tepida in this 3–8 cm depth layer was calculated by the Moran's Index and reveals lateral patches with a characteristic length of 1 to 2 cm. We investigate mechanisms potentially responsible for this distribution by observation of burrow structures and two-dimensional high-resolution imaging of dissolved iron. The surface maximum corresponded to the area of maximum oxygen availability. Observable burrows have no clear relation with the distribution of A. tepida but were closely related to dissolved iron distribution. Consequently, no evident relation between A. tepida and dissolved iron was observed. Nevertheless, two one cm-wide structures, enriched in dissolved iron produced by anaerobic degradation of labile organic matter, corresponded to increased A. tepida densities. This observation suggests that within strongly oxygen-depleted sediments, A. tepida could still be favoured by labile organic carbon. The main characteristics of the vertical distribution of A. tepida are interpreted in the present study as a combination of passive downward transport by biomixing into deeper suboxic (without both oxygen and sulfide) sediment layers and a subsequent mobility driven by a sensitivity to geochemical gradients. We hypothesize that the survival of A. tepida in oxygen depleted environments is explained its ability to lower its metabolism between periods of oxygen renewal by bioirrigation.
PY 2015
SO Biogeosciences
SN 1726-4170
PU Copernicus Gesellschaft Mbh
VL 12
IS 20
UT 000364323500009
BP 6219
EP 6234
DI 10.5194/bg-12-6219-2015
ID 38786
ER

EF