[B-PT04] Biomineralization and the Geochemistry of Proxies

[BPT04-P02] Biomonitoring in the Cassidaigne Canyon (NW Mediterranean): the resilience and recovery of deep-sea benthic foraminifera at a bauxite industrial waste site

*Pauline Duros¹, Christophe Fontanier^1,2,3, Briony Mamo^4,5, Deborah Mille⁶, Olivier Herlory⁶ (1.FORAM Research Group, F-49140 Villevêque, FRANCE, 2.Bordeaux University, EPOC Laboratory, UMR CNRS 5805 OASU, F-33615 Pessac, FRANCE, 3.Angers University, 4 boulevard Lavoisier, F-49000 Angers, FRANCE., 4.School of Biological Sciences, University of Hong Kong, Pokfulam Road Sai Wan, Hong Kong SAR, CHINA. , 5.Department of Biology, Macquarie University, North Ryde, NSW, 2109, AUSTRALIA., 6.CREOCEAN, Agence PACA Corse, 230 Avenue de Rome, Valparc-Bât B, F-83500 La Seyne sur Mer, FRANCE. )

Keywords:Benthic foraminifera, Bauxite residues, Cassidaigne Canyon, Resilience

During an environmental survey performed in autumn 2016, living (stained) benthic foraminiferal faunas were investigated at 16 stations sampled within the Cassidaigne Canyon (NW Mediterranean Sea) and surrounding area. For many decades, industrial bauxite residues of red mud have drained into the canyon via a submarine pipe, causing physical disturbance and chemical contamination. In January 2016, solid waste disposal ceased and was replaced with the dumping of a low-density liquid effluent. Stations investigated in this paper are located between 265–2500 m water depth from the shelf break to the deeper basin and from a distance between 4–70 km from the pipe outlet. At many sites, surface sediment is characterized by historical deposits of red mud and their geochemical imprints. Our ecological observations at the 725 m-depth station closest to the Cassidaigne Canyon submarine pipe show the highest concentration of the opportunistic and stress-tolerant species Bulimina marginata d’Orbigny, 1826, commonly identified as a recolonizer of disturbed areas. At the other fifteen stations, foraminiferal standing stocks and simple diversity (S) decrease with decreasing food input to the seafloor and increasing water depth. There, foraminiferal composition is characterized by a minor contribution of stress-tolerant species and echoes the overall meso-oligotrophic patterns of a relatively stable ecosystem. Our study clearly shows that in September 2016, 10 months after a historical shift in discharged industrial wastes (from dense red mud to liquid effluent), foraminiferal diversity close to the pipe outlet in the Cassidaigne Canyon remains altered, but appears to be slowly recovering.