SPATIOTEMPORAL STRUCTURE OF TIDALLY MIXED COASTAL WATERS - VARIABILITY AND HETEROGENEITY

In the tidally mixed coastal waters of the eastern English Channel, th e vertical properties of temperature, salinity, in vivo fluorescence, turbidity and light were investigated along an inshore-offshore transe ct, sampled in different tidal conditions. The vertical distribution o f these parameters was then characterized in terms of mean value, vari ability (i.e. standard deviation) and heterogeneity (i.e. fractal dime nsion), regarded as a quantitative characterization of the structure o f the vertical variability of both physical and biological parameters. These different estimates were then subjected to multivariate spatio- temporal analysis and showed a very specific spatio-temporal structure suggesting a differential control of the vertical properties of water masses;associated with both inshore-offshore gradient and tidal advec tion. In particular, the fractal dimension (i.e. heterogeneity) of in vivo fluorescence is higher during ebb for offshore waters, suggesting a density dependence of the phytoplankton biomass structure. In contr ast, the vertical variability of fluorescence is higher during flood f or inshore waters, leading to an inverse relationship between variabil ity and heterogeneity of the vertical distribution of phytoplankton bi omass.