Structure, fonctionnement, évolution des communautés benthiques ...

tel-00009359, version 1 - 1 Jun 2005
Chapitre 3 - Fonctionnement du réseau trophique benthique de la Grande Vasière
test, α = 0.05) between surface and bottom POM, but a number of benthic organisms (bivalves,
polychaetes, crustaceans) were significantly enriched in 13 C compared to some pelagic organisms
(C. echinulatus or L. typicus) or benthic suspension feeders (Ascidia or C. subterranea). There was
also a continuum of δ 13 C values in each taxonomic group.
Hierarchical cluster analysis (Ward’s minimum variance method) performed on data for stable
isotopic nitrogen and carbon ratios (Appendix A) identified three main groups of species on the
dendrogram (scission values of 91.4 and 27.1 respectively), two of which were divided into two
subgroups (scission values of 14.2 and 11.4 ; Figure 2).
Figure 2: Hierarchical clustering (Ward’s minimum variance method) of stable carbon and nitrogen
isotopes analysis from the ‘Grande Vasière’ benthic and demersal community.
When δ 15 N and δ 13 C are plotted together in a two dimension plane (Figure 3) three groups of
points are clearly identified 1: primary producers (surface POM and bottom POM), 2: consumers of
the primary production (zooplancton, suprabenthos, ascidians, Hyalinoecia fauveli and Callianassa
subterranea) and 3: others consumers. This last group can be decomposed into four sub-groups
according the hierarchical classification results.
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