|Structure du peuplement des invertébrés des zones halophiles de la Baie de Somme (Manche Orientale) = Structure of the invertebrate community of the salt marshes of the Bay of Somme (eastern English Channel|
Elkaim, B.; Rybarczyk, H. (2000). Structure du peuplement des invertébrés des zones halophiles de la Baie de Somme (Manche Orientale) = Structure of the invertebrate community of the salt marshes of the Bay of Somme (eastern English Channel. Cah. Biol. Mar. 41(3): 295-311
In: Cahiers de Biologie Marine. Station Biologique de Roscoff: Paris. ISSN 0007-9723, more
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Biocoenotics and comparative studies, between grazed and not grazed salt marshes (schorre), have been carried out in the Bay of Somme. Four sampling technics have been used (vacuum, berlese extraction, core sampling and reaping) and have shown a biodiversity of 96 species. They are mostly composed of continental species (91 species). Arthropods (92 species) show dominant densities for Acarina (41,1 %) and Collembola (29,7 %). The specific richness and densities of 21 taxonomic groups remain weak by comparison with those observed in the same ecosystems in North sea, English Channel or Atlantic. However we found a lot of typical species of salt marshes: Amphipoda Talitridae, Coleoptera Carabidae and Trechidae, Araneida Lycosidae. The distribution of species, studied by a multivariate analysis (AFC) may be explained by the influence of the gradient "Sea - Continent" associated to the hydric statement and the substrate which differentiate several types of habitat. The large numbers of sea walls which have been built successively since the last century and the perturbations they induced in the environment, have contributed to slow down and disturb the installation of the fauna.The grazing of ovine or bovine herds seems to favor globally a greatest specific and numeric richness, as well as the diversity of components of the food web in the occupied areas, probably by the important enrichment in organic matter (faeces). Comparative and statistical analyses of these structural parameters showed significant differences between the populations of the two sites, not grazed and grazed , and confirmed also the stability of the last zone.