Deep-sea benthic foraminifera in an area around the Cassidaigne Canyon (NW Mediterranean) affected by bauxite discharges

Abstract

During an environmental survey, living (stained) benthic foraminiferal faunas were investigated at 14 stations within the Cassidaigne Canyon (NW Mediterranean Sea) and the surrounding area. For many decades, industrial bauxite residues (namely red mud) have drained into this canyon via a submarine pipe. Stations investigated in this paper are located between water depths of 288 and 2,432 m from the shelf break to the deeper basin and at a distance ranging between~5 and 70 km from the pipe outlet. At almost every site, surface sediment is characterized by red mud deposits and their geochemical imprints. Our ecological observations show that foraminiferal standing stocks and simple diversity (S) decrease across the margin in response to the decreasing food input to the seafloor with increasing water depth. The foraminiferal composition echoes the overall mesooligotrophic patterns of our study area. The contribution of opportunistic and stress-tolerant species, commonly identified as recolonizers of freshly disturbed areas, is minor at the 14 stations. This clearly shows that red mud dispersal in the Cassidaigne Canyon and the surrounding area has no major ecological impact on foraminiferal diversity.

Cold-water coral ecosystems in Cassidaigne Canyon: An assessment of their environmental living conditions

“…Red bauxite has been discharged into the canyon at 320 m depth ( Fig. 1) by the Gardanne aluminum factory since 1967 (Dauvin, 2010;Fontanier et al, 2012) and red mud extends into the abyssal plain more than 50 km away from the pipe (Fontanier et al, 2014). For 21 years (from 1967 to 1988), the canyon was subjected to the massive discharge of bauxite residues of two different factories.…”

Novel benthic foraminifera are abundant and diverse in an area of the abyssal equatorial Pacific licensed for polymetallic nodule exploration

“…These more familiar taxa have been used to monitor the impact of anthropogenic activities on the marine environment since the late 1950’s6465. Over recent decades, the number of such studies has substantially increased from shallow66 to deep-sea67 environments. This led to the FOBIMO (Foraminiferal Biomonitoring) initiative, developed by a group of micropaleontologists to standardise methods by making a series of recommendations.…”

Evaluating the ecological status of cold-water coral habitats using non-invasive methods: An example from Cassidaigne canyon, northwestern Mediterranean Sea

“…These mean sizes are smaller than those measured at Cassis-200. We hypothesize that the small size of the population is a consequence of anthropogenic impacts occurring during the last 50 years (Dauvin, 2010;Fontanier et al, 2012;Fontanier et al, 2015;Fabri et al, 2017). The high sedimentation rate of bauxite residues may have prevented M. oculata's growth by suffocation, by starvation or by preventing settlement of new colonies.…”

“…After 1988 the discharge of bauxite residues was reduced as one factory stopped production. This disposal is known to have impacts on the local fauna of the canyon (Dauvin, 2010;Fontanier et al, 2012;Fabri et al, 2014;Fontanier et al, 2015;Fabri et al, 2017). Nevertheless, in an attempt to apply the protocols of the Barcelona Convention (1976), the French government decided to stop the disposal of red mud in January 2016, by granting a six-year license for the disposal of a fluid with no suspended matter and only chemicals, instead.…”

“…These potential suitable areas were inspected in 2017 with a Remotely Operated Vehicle (ROV) to validate the predicted habitat distribution and evaluate the status of populations of different species of benthic megafauna in relation to anthropogenic impacts. For 48 years (1967 to 2015), Cassidaigne canyon was subjected to massive discharges from the aluminum industry, which is known to have had impacts on the local fauna of the canyon (Dauvin, 2010;Fontanier et al, 2012;Fabri et al, 2014;Fontanier et al, 2015;Fabri et al, 2017).…”