This work is an interpretation of a chronological data set on abundances of estuarine soft substrate invertebrates using an ecological approach. The data were collected in the framework of the European programme COST 647 (Coopération Scientifique et Technique) on coastal benthic ecology which terminated in 1992. Species numbers and selected environmental factors were recorded at two stations in the Baie de Somme (France) from 1981 to 1992. Inter-annual and seasonal variations in benthos numbers were analysed using a plotting procedure based on a non-probabilistic approach, proposed by Andrews in 1972. Ecological groups of species were identified and succession in time described, coinciding with alterations in the landings of cockles Cerastoderma edule. The chronological data set was processed through the application of the cumulated function, giving directly intensity and duration of any changes in relation to the climate and water quality, especially potential eutrophication manifestations.