AN ALGORITHMIC MODEL FOR INVASIVE SPECIES - APPLICATION TO CAULERPA-TAXIFOLIA (VAHL) C. AGARDH DEVELOPMENT IN THE NORTH-WESTERN MEDITERRANEAN SEA

The purpose of the study is to evaluate the propagation of the green a lga of tropical origin Caulerpa taxifolia (Vahl) C. Agardh in the nort h-western Mediterranean sea-introduced in 1984-by means of an algorith mic computer model. In order to take into account spatial interactions and anthropic dispersion or activities such as eradication and introd uction of specific predators, the model is based on a coupling of a ge ographical information system (GIS) with a stochastic discrete event s imulation. Even if the model has to cope with incomplete data and samp ling difficulties encountered in the hostile environment of the sea, i nteresting calibration and validation procedures have been achieved, i ncluding spectral analysis of spatial simulation results. At this stag e, the model seems capable of achieving a certain level of prediction: local pattern of expansion, increase of C. taxifolia biomass and cove red surfaces, and invasive behaviour towards existing communities. (C) 1998 Elsevier Science B.V. All rights reserved.