Equilibria or not? How will deep-sea mining affect benthic marine communities?

Attempts are underway for large-scale industrial mining for rare earth elements on the ocean floor. Using data from marine meiofauna, we examine whether communities disturbed or destroyed by localized mining will recover and re-establish the original equilibria. Studies of beach meiofauna are more detailed than comparable studies of deep-sea meiofauna, permitting the conclusion that many meiofaunal species do not produce many offspring fast nor disperse widely. Cosmopolitan species are rare. Previous studies have shown an enormous species diversity and the presence of many new taxa. Detailed surveys are necessary of more beach and deep-sea habitats including biological observations. Environmental DNA studies of deep-sea sediments are essential but cannot replace taxonomic studies using morphology and DNA analysis of species. Discovery rates of new species are not a reliable measure for completeness of estimates in largely unexplored biomes. Since we do not even know the taxonomic composition of the benthic fauna, it is impossible to determine whether habitats are in equilibrium or not. However, high endemicity and limited dispersal suggest that equilibrium conditions are uncommon. Therefore, it is illusory to expect that habitats will return to an equilibrium after mining. Industrial exploitation on the ocean floor should be preceded by detailed and long-term taxonomic and biological studies.