Le mercure, le cadmium et le plomb dans les eaux littorales libanaises: apports et suivi au moyen de bioindicateurs quantitatifs (éponges, bivalves et gastéropodes)

In 1975, the meeting for the protection of the Mediterranean Sea in Barcelona fixed several important objectives. One of them was the creation of National Observation Programs in order to evaluate the levels and tendencies of pollutants. Furthermore the MED-POL program has re-evaluated and developed these objectives. Lebanon has signed the Barcelona Convention and has been engaged in providing data about its coastal water quality. Unfortunately the Lebanese war, which also began in 1975, paralyzed the country for 15 years. Since 1990, successive governments in the country have fixed as an objective the reconstruction of the tourism sector. As a consequence, they became interested in the environmental problems. The studies carried out before or during the war are not sufficient to provide all the necessary data for the evaluation of contaminant levels in the Lebanese marine ecosystem especially after the demographic explosion and the absence of regulation during the war. The creation of a National Observation Net has become a vital need and a project with socioeconomic interest. The aim of this work is to establish a National Observation Net adapted to the Lebanese coast. It is constituted by an evaluation of the contamination levels of cadmium, lead and mercury along 50 km of the Lebanese coastal area by direct analysis of sea and river waters, effluents and sediments, and also by the development of quantitative biological indicators. The results allow us to evaluate and identify pollution point sources and to assess the contribution of each contamination source in the enrichment of the coastal waters by these three metals. Three bioindicators (Brachidontes variabilis, Patella sp. and Hippospongia communis) have been validated by comparison of their metal concentrations with metal levels found in water and by using a new technique of pure chemical concentration known as Diffusive Gradients in Thin Films (DGT). For a future network, we propose the use of the bivalve and the gastropod as passive bioindicators, and sponge transplants as active biomonitoring complementary tools.