Experimental Re-establishment of a Soft Bottom Community: Utilization of Multivariate Analyses to Characterize Different Benthic Recruitments

In situ community development was studied in the southern North Sea, using containers of defaunated sediments placed at the entrance of Dunkerque west harbour in order to simulate a possible faunal recovery. After a lag phase during which the pollution load (essentially heavy metals) was partially abated, development was characterized by a progressive increase in number of taxa, density and biomass. Diversity increased with the increasing colonization periods for samples collected during the same season. The dominant taxon was Polychaeta. In the experimental environment, larval recruitment accounted for the greatest proportion of all colonizing individuals (approximately 70%). With the help of multivariate analyses different recolonization scenarios were observed, all of which can be described in terms of successive recruitments. We distinguished four principal recruitments recorded as α, β, γ, δ and several secondary ones, characteristic of the season of immersion. Almost all the species concerned belong to the Abra alba community which predominates in the natural surrounding area