The abyss between 3,000 and 6,000 m water depth is the largest ecosystem on our planet. The growing industrial interest in mining of metal-rich polymetallic nodules threatens the abyssal plains. Nodule extraction will have deleterious effects on the ecosystem and the generated sediment plumes will have the spatially largest impact. The plumes will affect deep-sea glass sponges, one of the most important ecosystem engineers in the deep sea, directly and indirectly over hundreds to thousands of square kilometers. This Rubicon project will experimentally address the direct impacts of the sediment plume on glass sponges by 1) assessing differences in smothering risks among different sponge morphologies and 2) analyzing whether the plume affects sponge metabolism and feeding efficiency. The plume may indirectly influence sponges if it causes an impaired heterotrophic production of the food source of glass sponges, the bacterioplankton. Therefore, this Rubicon project will also investigate experimentally 3) how the heterotrophic biomass production and community composition of bacterioplankton changes inside the sediment plume. The outcome of this Rubicon project will help to define thresholds for particle concentrations in deep-sea mining-induced sediment plumes that the International Seabed Authority can directly im-plement into its new Mining Code.