POLLUTION IMPACT STUDY IN GABES GULF (TUNISIA) USING REMOTE-SENSING DATA

A multidisciplinary project was conducted to study the impact of an important phosphogypsum discharge (50 million tons discharged near Gabes city over twenty years). Analysis of remote sensing data (Landsat MSS, SPOT XS and P, NOAA AVHRR) combined with field measurements were used to describe actual and historical states and begin understanding alteration mechanisms. The satellite information concerns bottom changes, sea color, sea surface temperature, and swell. Drastic changes have occurred in the Gabes Gulf to the west of the Gneiss-Djerba sill. The seagrass beds and Caulerpa fields that covered most part of the Gulf are now restricted to some areas upwards of 10m depth. Under hydrodynamic processes, bare sediments can be re-suspended more easily. Light reaching the bottom is reduced, inducing a shift from bottom primary production to a planktonic one. Other contributory factors are discussed.