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| Titel |
Two-dimensional distribution of living benthic foraminifera in anoxic sediment layers of an estuarine mudflat (Loire estuary, France) |
| VerfasserIn |
A. Thibault de Chanvalon, E. Metzger, A. Mouret, F. Cesbron, J. Knoery, E. Rozuel, P. Launeau, M. P. Nardelli, F. J. Jorissen, E. Geslin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 20 ; Nr. 12, no. 20 (2015-10-29), S.6219-6234 |
| Datensatznummer |
250118146
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| Publikation (Nr.) |
 copernicus.org/bg-12-6219-2015.pdf |
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| Zusammenfassung |
| We present a new rapid and accurate
protocol to simultaneously sample benthic living foraminifera in two
dimensions in a centimetre-scale vertical grid and dissolved iron and
phosphorus in two dimensions at high resolution (200 μm). Such an
approach appears crucial for the study of foraminiferal ecology in highly
dynamic and heterogeneous sedimentary systems, where dissolved iron shows a
strong variability at the centimetre scale. On the studied intertidal mudflat
of the Loire estuary, foraminiferal faunas are dominated by Ammonia
tepida, which accounts for 92 % of the living (CellTracker Green(CTG)-labelled) assemblage.
The vertical distribution shows a maximum density in the oxygenated
0–0.4 cm surface layer. A sharp decrease is observed in the next 2 cm, followed by a second, well-defined maximum in the suboxic
sediment layer (3–8 cm depth). The presented method yields new information
concerning the 2-D distribution of living A. tepida in suboxic
layers. First, the identification of recent burrows by visual observation of
the sediment cross section and the burrowing activity as deduced from the
dissolved iron spatial distribution show no direct relation to the
distribution of A. tepida at the centimetre scale. This lack of
relation appears contradictory to previous studies (Aller and Aller, 1986;
Berkeley et al., 2007). Next, the heterogeneity of A. tepida in the
3–8 cm depth layer was quantified by means of Moran's index to identify the
scale of parameters controlling the A. tepida distribution. The
results reveal horizontal patches with a characteristic length of 1–2 cm.
These patches correspond to areas enriched in dissolved iron likely generated
by anaerobic degradation of labile organic matter. These results suggest that
the routine application of our new sampling strategy could yield important
new insights about foraminiferal life strategies, improving our understanding
of the role of these organisms in coastal marine ecosystems. |
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