Impacts of Deep-Sea Mining on Microbial Ecosystem Services

Abstract

32Interest in extracting mineral resources from the seafloor through deep-sea mining has 33 accelerated substantially in the past decade, driven by increasing consumer demand for various 34 metals like copper, zinc, manganese, cobalt and rare earth elements. While there are many on-35going discussions and studies evaluating potential environmental impacts of deep-sea mining 36activities, these focus primarily on impacts to animal biodiversity. The microscopic spectrum of 37 life on the seafloor and the services that this microbial realm provides in the deep sea are rarely 38 considered explicitly. In April 2018, a community of scientists met to define the microbial 39 ecosystem services that should be considered when assessing potential impacts of deep-sea 40 mining, and to provide recommendations for how to evaluate these services. Here we show that 41 the potential impacts of mining on microbial ecosystem services in the deep sea vary 42 substantially, from minimal expected impact to complete loss of services that cannot be remedied 43 by protected area offsets. We conclude by recommending that certain types of ecosystems should 44 be "off limits" until initial characterizations can be performed, and that baseline assessments of 45 microbial diversity, biomass, and biogeochemical function need to be considered in 46environmental impact assessments of all potential instances of deep-sea mining. 47 48 49KEYWORDS (5-8): deep-sea mining, ecosystem services, hydrothermal vents, inactive 50 sulfides, ferromanganese nodules, cobalt crusts, seamounts, marine microbiology 51 52

Inactive Sulfide Ecosystems in the Deep Sea: A Review

“…Potential impacts of mining on seafloor massive sulfides have been reviewed in multiple published articles, including (Van Dover, 2011Boschen et al, 2013;Levin et al, 2016;Van Dover et al, 2017;Jones et al, 2018;Niner et al, 2018;Orcutt et al, 2018;Weaver et al, 2018); only a précis is provided here. Open-pit mining of inactive sulfide deposits as proposed by contractors (e.g., Gwyther, 2008) will result in modification of seabed topography (from mound to pit) and thus of circulation patterns at small spatial scales of 10's meters or more horizontally and 10's of meters vertically.…”

“…Stimulation of heavy-metal metabolizing microbes by mining activities may affect element cycling in the deep sea, including increased concentrations of bioavailable metals and biologically mediated precipitation (Orcutt et al, 2018). Because inactive sulfides are not associated with high temperature and acidic fluids that mediate metal dissolution in active hydrothermal systems, they have been deemed likely to be more 'ecofriendly' in this regard than active sulfides as a target for mining (Fallon et al, 2017).…”

“…Sulfuric acid generation by abiotic sulfide oxidation during mining operations (acid mine drainage) seems unlikely to exceed the buffering capacity of seawater (Bilenker et al, 2016), though a contrary view suggests that in an open-pit mining scenario, there is potential for ponding and the possibility of local acidification and anoxia (Orcutt et al, 2018). Natural 'capping' of sulfide minerals by insoluble metals such as iron-oxyhydroxides through abiotic and biotic processes may be sufficiently rapid to serve as a passive mitigation action against acid mine drainage (Edwards, 2004).…”

“…Active mitigation of a hypothetical oxygendepleted and acidic 'pond' or pit seems plausible through selective contouring during mining operations to ventilate the depression. This or other potential mitigating actions [e.g., capping with introduced materials (Orcutt et al, 2018)] must not do more harm to the environment than good. The operational scale, mineral complexity, and biological activity of inactive sulfide systems all indicate that assessment of the environmental risk and monitoring of dissolved metals and of metal burdens outside the direct impact zone will be important components of environmental management plans, if and when mining of inactive sulfides on the seafloor is permitted (Hauton et al, 2017).…”

Rimicaris exoculata: biology and ecology of a shrimp from deep-sea hydrothermal vents associated with ectosymbiotic bacteria

“…the ability to cope with the modifications and to rebuild after disturbances) is still too incomplete to assess the risks associated with this activity, or to predict the impacts of a possible exploitation. There are still too many crucial gaps regarding biodiversity or functioning of hydrothermal ecosystems (Boschen et al 2013, Orcutt et al 2020.…”