At The Interface of Ocean Sciences and Society: Ecological Aspects of Deep-Sea Mining

The deep-sea realm, commonly defined as the area deeper than 200m, covers >60% of the surface of Earth and is its largest biome. Globally relevant functions of the deep sea in the carbon cycle are the long-term storage of large quantities of carbon in the form of sedimentary organic matter and carbonates, and short-term biological remineralization of matter sinking from the surface, returning nutrients for ocean productivity. Furthermore, the deep-sea biome is fantastically rich in habitats, species and thereby genetic resources. The Census of Marine Life program estimated a diversity of a million animal and a billion microbial taxa, many of which remain to be discovered in the abyss. A third category of riches are reservoirs of ores, including polymetallic sulphides, manganese nodules, cobalt-rich ferromanganese crusts, and metals of the rare earths. This presentation will focus on the ecological framework of mining of such ore resources, which could be in conflict with the preservation of the biological resources and hence needs environmental management.

In this regard, the deep-sea remains a fascinating research area for discovery, as less than a per-mill of its total area has been seen and studied, and little is known as to its natural dynamics. As deep-sea research infrastructure is expensive and of limited availability, progress in environmental monitoring and management is slow, compared the speed of anthropogenic change as by the recent climate warming, or by ocean pollution. Main current direct impacts are from deep-sea fisheries, deep-sea oil extraction, deposit of debris and pollutants, deep-sea cabling, and resource exploration. These so far concern only a small proportion of the total space, especially in the high seas, outside of the national economic zones. This could rapidly change, if economic pressures call for the deep-sea exploitation of metals such as copper or nickel, which may limit further economic growth, much before oil and fish.

This presentation will discuss the needs for contributions from ocean sciences to provide knowledge to help regulating potential impacts from future deep-sea mining. Especially with regard to ore mining, for it to be commercially viable, it will affect large areas of the deep-sea environment by disturbing the seafloor and the overlying water column, by removing seafloor substrate, and by the dispersion of sediment plumes and mining debris. The presentation will provide first results of the revisit to the DISCOL “disturbance and re­colonization”- experiment by SONNE expedition SO242 in 2015, 26 years after the initial disturbance by ploughing a manganese nodule area of > 1 km² at 4150 m water depth in the Southeast Pacific. In the framework of the European programs JPI Oceans and MIDAS, this area was studied intensively with deep-sea robots, camera tows and landers, to assess changes in ecosystem functions compared to undisturbed area. This presentation will also touch upon how ocean scientists can engage in policy making for marine ecosystem management, and what needs there are in education, science communication and research funding at the interface of ocean sciences and society. Among the key tasks of ocean sciences are to inform about the ecological principles and technologies of baseline and impact monitoring, as well as to the knowledge on spatial and temporal scales of disturbances, resilience and recovery potentials of deep-sea ecosystems, such as abyssal plains, seamounts and ridge environments.