[M-ZZ47] Marine Manganese Deposits - Genesis, environment, and development -

[MZZ47-P04] How will Deep Sea Mining Affect Sulfide and Nodule Environments?

*Travis William Washburn¹, Akira Iguchi¹, Kyoko Yamaoka¹, Yosuke Onishi², Nobuyuki Okamoto^3,4, Atsushi Suzuki¹ (1.National Institute of Advanced Industrial Science and Technology, 2.KANSO Co., LTD, 3.Japan Oil, Gas and Metals National Corporation, 4.Kobe University)

Keywords:deep sea mining, seafloor massive sulfides, manganese nodules, benthic communities, heavy metals, environmental impact assessment

Full-scale mining of deep-sea resources may occur within the next few years given the call in 2021 for the International Seabed Authority to finalize mining regulations for manganese nodules. Many questions about the communities associated with habitats where mining will likely occur remain, including their resilience to human activities. Much of what is currently known about possible impacts from mining comes from past disturbance tests on nodule-rich areas. This presentation aims to put the results of sulfide mining in the context of lessons learned from these past studies. This presentation will discuss results from the first-ever mining disturbance test on deep-sea seafloor massive sulfides on benthic infaunal communities, from bacteria to macrofauna. Impacts from mining include habitat removal, sedimentation, and increased heavy-metal concentrations. Many factors likely affect the level of mining impacts to the surrounding environment such as distance, current direction, and local topography. While all sulfide communities examined appeared to exhibit some changes from the disturbance test, both the spatial and temporal extent of impacts varied among different size components of the benthic community as well as different community variables (i.e., abundance, diversity, and community structure). Results of this sulfide disturbance will be compared to previous nodule disturbance tests in the Clarion-Clipperton Zone and elsewhere. Benthic communities often show similar patterns to disturbance regardless of the type of disturbance or habitat, but there are also many reasons to expect differences in how communities respond in sulfides vs. nodules. This work will hopefully provide valuable information on deep-sea benthic resilience to deep-sea mining and guide both the ISA and mining contractors towards best practices to mitigate damages from future exploitation.