Structural evolution of two suprabenthic soft-bottom communities of the South Gascogne continental shelf
Jean-Claude Sorbe

A survey of two sites (situated on a E-W bathymetric transect off Arcachon Bay) was carried out from January 1981 to March 1982. Analysis of the motile fauna sampled monthly by means of a quantitative sledge shows the existence of two distinct suprabenthic communities in relation to the depth gradient. The structural evolution of the coastal community (31 m depth; unstable sediments) reflects the severe and fluctuating environmental conditions of this area: dominance of a reduced number of species, low species richness and diversity indices, strong fluctuations of density and biomass values, alternation of log-linear with log-normal demographic profiles. some frequency rank curves with typical features of juvenile assemblages. At a deeper site (91 m depth; muddy sand sediments), the more stable environmental conditions lead to a community structure organized in a different way from that of the coastal one (either in its daytime or night-time aspect): higher values of species richness and diversity indices, most demographic profiles in close conformity to the log-normal model of abundance distribution, convex shape of all the rank frequency curves. Comments are made about the indirect role of hydrodynamic action on the structure of these suprabenthic communities.

Keywords: suprabenthos, soft bottoms, structure, benthos communities, Arcachon.
Contents of this volume Sci. Mar. 53(2-3) : 335-342 Back PDF
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