A TYPOLOGY BASED ON THE SHAPE OF CHRONOLO GICAL SERIES (TSS)

The typology of shapes of series (TSS) aims to gather together species having similar temporal patterns corresponding to different types of ecological behaviour. Each type of change, referred to as the ecologic al shape, is considered to reflect a particular demographic strategy ( sudden pullulation of opportunistic species, fluctuations with environ mental changes, etc.). This method which consists in the definition of four shape parameters and a classification among the series, taking i nto account these shape parameters, does not replace the usual statist ical analyses, mainly multivariate ones, but precedes them. Such preli minary information is useful for the choice of the subsequent treatmen ts, avoiding the need to analyse simultaneously species presenting dis tinct types of ecological responses. The TSS method was applied to fou r macrobenthic communities of the English Channel and the south of the North Sea, sampled from 1977 to 1992. Clustering among the ecological shapes revealed six different groups. Analysis of species lacking abu ndance (very scarce or absent during at least five years) and of speci es presenting high anomalies (higher than three standard deviatiations ) showed thar ecological responses of this type can be related To envi ronmental factors such as temperature, atmospheric pressure or the ''A moco Cadiz'' oil spill in 1978.