CHARACTERIZATION OF SPACE-TIME VARIABILITY IN STRATIFIED AND MIXED COASTAL WATERS (BAIE DES CHALEURS, QUEBEC, CANADA) - APPLICATION OF FRACTAL THEORY

The variability of in vivo fluorescence, temperature and salinity in t he vertically stratified and well-mixed waters of the Bale des Chaleur s (Quebec, Canada) was investigated as a continuous function of scale by applying the concept of fractal dimension to variogram analysis. Wi dely applied to the description of spatial heterogeneity, fractal dime nsion appears here to be a helpful descriptive tool in discriminating between homogeneity and heterogeneity in time series of both physical and biological parameters. In stratified waters, the structuration of in vivo fluorescence, temperature and salinity remains the same over t ime, in spite of mixing induced by the rise of a strong wind, and is s hown to be associated with the global structure of the water column. I n mixed waters, the situation is more complex, giving rise to specific behaviour of in vivo fluorescence and salinity. In both cases, the di fferences observed between the fractal dimensions can be explained in terms of different ranges of scales perceived in pattern variability a nd thus, in the complexity of the pattern structure. We also suggest t hat the departure from strict selfsimilarity which seems to be associa ted with the vertical structure of the residual circulation is an indi cator of the transitional zone between different levels of system orga nisation.