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. Seawater physical-chemical parameters were measured daily in each aquarium. Temperature and pH were measured manually in each aquaria every day using a Mettler-Toledo Seven2Go pH /Ion meter S8, salinity was measured with a S30 SevenEasyTM conductivity meter and oxygen concentration was measured with a Fibox4 (PreSens) with a Oxygen Dipping Probe DP-PSt3.

Species: Dentomuricea aff. meteor1. Experimental treatmentsControl: no particle additionPMS10: Polymetallic sulphides at a concentration of 10 mg/lPMS50: Polymetallic sulphides at a concentration of 50 mg/lNFS10: Nodule field sediments at a concentration of 10 mg/lNFS50: Nodule field sediments at a concentration of 50 mg/lParticles delivered daily in 12 hours cycles