The Mediterranean Mussel Watch : a Regional Program for Detecting Radionuclides and Trace-Contaminants

Titre du congrès :15th International Bioindicators Conference Ville du congrès :Hong-Kong Date du congrès :07/06/2007

A regional bio-monitoring program has been implemented using mussel as a selected bio-indicator with the pro-active involvement ofsome 20 marine environmental labo-ratories from 15 different Mediterranean countries. In 2002, a dedicated workshop was called to design a permanent Mediterranean Mussel Watch (MMW) aiming to organize the production ofmonitoring data on a common basis and to set up an effec¬tive observation tool on an extended scale. A common agreement was reached on the objectives and the general framework ofthe monitoring network, including strategies, procedures and methods. The main objectives are to develop an international trans-Mediterranean infrastructure of cooperating scientists and laboratories aiming at monitoring levels of selected contaminants in coastal waters andfirst to document reli-able baseline levels of radionuclides in the Mediterranean and Black Sea coastal waters. The selected bio-indicator specie is the Mediterranean mussel Mytilus gallo-provincialis, widespread in the region and for which background knowledge on biol-ogy and physiology is available. In sectors where naturals populations are rare or absent, samples can be obtained from transplanted mussels. More than 50 sites have been sampled sofar, usually before and after the spawning season, although the south and east coasts are still poorly documented. Sampling procedures and treatment of samples is homogenous among the participants. Trace level measurements of radionu¬clides are performed by direct gamma spectrometry as a routine technique. Initial intercalibration ofall participating analytical laboratories was a very important step in the implementation phase. This was achieved with the making ofa specific reference material (AIEA-437), used to carry out a large inter-comparison exercise across the entire network. The MMW network in 2005 produced the first distribution map of 137Cs at the regional level. This artificial radionuclide, which primarily originated from global fallout of former nuclear weapons tests, is now detected at a very low level (usually less than 1 Bq.kg-1 w.w.) in all Mediterranean coastal waters. However, in the Black Sea and North Aegean Sea, 13 7Cs activity in mussels is still above one order of magnitude higher than in the Western basin, showing the remaining impact ofthe Chernobyl accident. In the next step, radionuclides measurements should be extended to 210Po and some plutonium isotopes. The second phase will then concern some selected chemical emerging contaminants.