The authorization to discharge into the sea, in the Cassidaigne canyon, from the Alteo GARDANNE alumina plant ended on 12/31/2015. However, the plant requested two new authorizations: one for occupation of the public maritime domain with its pipeline and another for a derogation for a new discharge. Although representing a reduced flow of contaminants discharged compared to the existing one, this new discharge did not allow all the standards of the decree of February 2, 1998 to which the plant is subject. Therefore, the Ministry of Ecology, Sustainable Development and Energy had entrusted ANSES and Ifremer with an additional study on the chemical contamination of marine organisms in the area affected by the industrial discharge, namely in the Cassidaigne canyon. In fact, the existing data did not allow a conclusion to be drawn on the existence or not of a risk linked to the consumption of fishery products in the area.

Ifremer was mandated to participate with ANSES in drafting the sampling protocol, to implement it and provide ANSES with samples for chemical analyzes and to assist ANSES in processing and statistical analysis of the results. The prescribed sampling protocol contained two parts: the first based on the establishment of artificial mussel stations in the area and the second relating to the sampling of about twenty species exploited in the affected area but also from a reference area (located in the bay of Hyères). The Alteo 2015 campaign, carried out with the Oceanographic vessel Tethys II on June 10 and 11, 2015, made it possible to position 18 artificial mussel stations on the impact zone of the Alteo plant discharge and thus respond to the referral from the Ministry in charge of the environment. The figure underneath present the position of the stations. The recovery of these stations was carried out in August 2015, 2.5 months after the immersion, with the GGIX vessel of the company XSurvey.

Position of artificial mussels stations during the Altéo campaign.
The green reference stations are data acquired during RINBIO 2015 campaign.

At each station, the concentration of metallic trace elements in the mussels, in particular aluminum, vanadium and titanium, markers of discharge, were analyzed by the ANSES laboratory.