Beyond deep-sea mining sublethal effects: Delayed mortality from acute Cu exposure of the cold-water octocoral Viminella flagellum.

Abstract

The potential release of metals, especially copper (Cu) during mining of seafloor massive sulphides (SMS), represents a potential toxicological threat to cold-water coral (CWC) habitats. Herein, we evaluated for the first time the response of the whip coral Viminella flagellum to short-term acute Cu exposure. Nubbins of V. flagellum were exposed to Cu concentrations of 0 (control); 60; 150; 250; 450 and 600μg/L for 96h. After exposure, V. flagellum nubbins were transferred to a continuous flow-through aquarium and feed once a day for 3weeks. No immediate mortality was detected during the short-term Cu exposure. However, a delayed mortality, which was concentration dependent was observed. The first signs of tissue loss occurred after 1week of recovery in non-contaminated conditions in V. flagellum nubbins previously exposed to Cu concentrations of 60 and 150μg/L followed by nubbins exposed to Cu concentrations of 250, 450μg/L after 2weeks and 600μg/L after 3weeks. A delayed mortality impact should be considered in future Cu tolerance experiments and scenarios of deep-sea mining exploitation.