Ecotoxicological risk assessment (accumulation of metals and biomarkers responses) using the hydrothermal vent shrimp Rimicaris exoculata, in situ and after copper exposure

Supervisor: Maria Bebianno (Centre for Marine and Environmental Research (CIMA), Universidade do Algarve, Faro (Portugal)
Massive-sulfide deposits, rich in metals with important commercial value, will be targets to the deep-sea mining industry. However, few data is available on the ecotoxicological risks to the deep-sea fauna, but this is key information to better understand the potential environmental impact of mining in organisms living in the deep sea. Taking into account the environmental conditions prevailing in the deep sea, such as the high pressure and low temperature, there is an urgent need to develop toxicity testing protocols adapted to the deep-sea environment. This study reports on the in situ values for metals content and biomarkers levels in different tissues of Rimicaris exoculata collected from TAG (Trans Atlantic Geotraverse) (26° 8.2’N, 44° 49.5’W) vent field in the Mid-Atlantic Ridge with 3630 m depth (isobaric sampling) during the BICOSE cruise in 2014. In addition, the biomarkers response in the different tissues after on board copper exposure at in situ pressure (30 MPa) using the high-pressure aquarium IPOCAMP (Incubateur Pressurisé pour l’Observation en Culture d’Animaux Marins Profonds), are also reported. Tissue metal accumulation was quantified in gills, hepatopancreas and muscle, and a battery of biomarkers was measured: metal exposure (metallothioneins), oxidative stress (catalase, glutathione-S-transferase) and oxidative damage (lipid peroxidation). Results show that metal accumulation is tissues dependant. The same range of metal present in the hot fluid composition was found in shrimp tissues. Cu is more concentrated in the hepatopancreas and redistributed to the gills after incubations (to both exposed groups). Significant induction of metallothioneins was observed in the gills of shrimps exposed to 4μM of Cu compared to the control group. Moreover, antioxidant enzymes activities were higher in gills, with a slight increasing trend with the increase in Cu concentrations exposure. An opposite trend was observed for lipid peroxidation in gills. Mechanisms of protection established seem to have a beneficial effect on the decreasing of ROS attack on membranes. Moreover, results suggest that the toxicity testing protocol used, including a physiologically critical step of pressurizing and depressurizing the test chamber to enable the seawater exchange during exposure to Cu, did not significantly affect the biomarkers response and may prove to be a ready to use method to assess the toxicity to contaminants in deep-sea species. Nevertheless, further studies are needed, that include the analysis of other physiological and biochemical parameters, other species and chemical contaminants. Keywords :TAG site, Rimicaris exoculata, Copper exposure, Biomarkers.