In 1983, mercury was with the prize list of pollution by heavy metals. It is present at the natural state in certain ores and the volcanic emanations; with the rains and scrubbing, it is found in the oceans a tan average rate of 0.5 mg/1 with 3 mg/1.

        To these two principal natural sources come to be added many other sources coming from the human activity. I thus will present some of these sources to you which pollute the seas and the marine biotope:

	- during the extraction and of the netting of cinnabar ore, a mercury sulphide accounting for 2 to 3 % of treated metal is rejected in the form of vapor or of particles
	- mercury derivatives like chloride mercuric or the acetate of phenyh mercure, used like fungicide and bactericide in the packing of the seeds because same of their toxicity
	- the chemical industry uses mercury for obtaining chlorine and soda per electrolysis
	- mercury is largely employed in the manufacture of electric measuring equipment   .   Little recycled, it finished its days in nature or the oceans
	- worn piles

        The mercury discharge in water is 3.6 kg.

       The mineral mercury which arrives in the marine ecosystem is transformed into various compounds mercuriels, according to the physicochemical conditions of the medium. Most dangerous being methyl mercury because of its great stability and these cumulative effects, there can remain indosable in sea water, but he is collected and filtered by micro-organisms such as the phytoplankton; he is concentrated there after by the successive consumers.