Changements à long terme dans une communauté benthique d'un golfe méditerranéen (golfe de Fos)
Changes over a period of thirty years in a circalittoral mud community (% silt greater than or equal to 75) in the Gulf of Fos (French, Mediterranean coast) have been followed at three sites spaced along a transect NNW-SSE at depths of 15, 35 and 70 m. The results clearly show how the macrobenthic community at the three sites has been influenced by the construction of the port of Fos, notably as a consequence of sediment suspension during the dredging of the docks and the access channel, but also due to the dumping at sea of dredged material (more than 100 x 10(6) m(3) were dredged, about a quarter of which was dumped at sea, at depths of 30 to 60 m). The grouping of the samples taken before, during and after the development of the port (1963-1964, from 1972 to 1979 and 1984 to 1993), by principal component analysis (PCA) and by parsimonious analysis, a method derived from cladistic phylogeny, together with the variations during this period of certain descriptive factors (species diversity, abundance of biological indicators), show that: 1) in shallow water (15 m) and on the dumping sites (35 m) the community changed considerably; 2) after the completion of the port development, the community at these two sites not only remained very different from the original community, but also failed to achieve a new equilibrium; 3) in deeper water, even when under the influence of the port construction, there was no fundamental change in the nature of the community; and 4) variations in the outflow of the Rhone river during this period cause changes linked to climatic events that act in addition to those resulting from human disturbance.
Auteurs du document :
Salenpicard, C, Bellan, G, Bellansantini, D, Arlhac, D, Marquet, R