The polymetallic (sometimes called ‘manganese’) nodules on the soft sediments in the Clarion-Clipperton Zone in the Pacific Ocean, play a very important role. They provide hard-substrate habitat for immobile animals, such as corals and sponges, which in turn provide habitat for other animals. A famous example for such highly specialized associations is the deep sea ghost octopus (nicknamed ‘Casper’): it wasn’t until recently, that scientists discovered that these nodules function as breeding grounds for deep-sea ghost octopuses which lay their eggs on sponges that only grow on these nodules and then guard them, likely for years before hatching. Without these polymetallic nodules, the sponges would not be able to grow in the soft sediments – and without sponges ‘Casper’ the ghost octopus would not find a place to lay eggs and reproduce.
Nodule collection will remove the habitat of deep-sea fauna, and because the nodules take millions of years to form, the removal of habitat may effectively be permanent. It is unlikely that the deep-sea ecosystems would ever fully recover after Deep Sea Mining activity.