Suspended sediment concentrations during an ex-situ experiment on the effects of simulated deep-sea mining sediment plumes on the cold-water octocoral Dentomuricea aff. meteor in the Azores

We report the results of an aquaria-based experiment testing the effects of simulated sediment plumes generated during mining activities for the extraction of ferromanganese nodules in the Clarion-Clipperton Fracture Zone (CCFZ), northeastern equatorial Pacific Ocean, and seafloor massive sulfides from a hydrothermal vent field in the Azores, northeast Atlantic, on the physiology of the cold-water octocoral Dentomuricea aff. meteor. Coral fragments were exposed to five experimental treatments for a period of four weeks at the DeepSeaLab aquaria facilities (Okeanos-University of the Azores): (1) suspended plumes of abyssal sediments from nodule fields at a concentration of 10 mg/l; (2) suspended plumes of abyssal sediments from nodule fields at a concentration of 50 mg/l; (3) hydrothermal polymetallic sulphide particles at a concentration of 10 mg/l; (4) hydrothermal polymetallic sulphide particles at a concentration of 50 mg/l; and (5) a control treatment with no sediment addition. Sediments were added in 12 h daily cycles. The concentration of suspended sediments in each aquaria were monitored twice a week by filtering seawater and weighing sediments.