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

• Autores: J.C. Sorbe
• Localización: Scientia Marina, ISSN 0214-8358, Vol. 53, Nº. 2-3, 1989, págs. 335-342
• Idioma: inglés
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• Resumen

  • 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.