Impacts of deep‐sea mining on microbial ecosystem services

Abstract

Interest in extracting mineral resources from the seafloor through deep-sea mining has accelerated in the past decade, driven by consumer demand for various metals like zinc, cobalt, and rare earth elements. While there are ongoing studies evaluating potential environmental impacts of deep-sea mining activities, these focus primarily on impacts to animal biodiversity. The microscopic spectrum of seafloor life and the services that this life provides in the deep sea are rarely considered explicitly. In April 2018, scientists met to define the microbial ecosystem services that should be considered when assessing potential impacts of deep-sea mining, and to provide recommendations for how to evaluate and safeguard these services. Here, we indicate that the potential impacts of mining on microbial ecosystem services in the deep sea vary substantially, from minimal expected impact to loss of services that cannot be remedied by protected area offsets. For example, we (1) describe potential major losses of microbial ecosystem services at active hydrothermal vent habitats impacted by mining, (2) speculate that there could be major ecosystem service degradation at inactive massive sulfide deposits without extensive mitigation efforts, (3) suggest minor impacts to carbon sequestration within manganese nodule fields coupled with potentially important impacts to primary production capacity, and (4) surmise that assessment of impacts to microbial ecosystem services at seamounts with ferromanganese crusts is too poorly understood to be definitive. We conclude by recommending that baseline assessments of microbial diversity, biomass, and, importantly, biogeochemical function need to be considered in environmental impact assessments of deep-sea mining.With increasing demand for rare and critical metals-such as cobalt, copper, manganese, tellurium, and zinc-there is increasing interest in mining these resources from the seafloor (Hein et al. 2013; Wedding et al. 2015;Thompson et al. 2018). The primary mineral resources in the deep sea that attract attention fall into four categories (Figs. 1, 2): (1) massive sulfide deposits created at active high-temperature hydrothermal vent systems along mid-ocean ridges, back-arc spreading centers, and volcanic arcs, from the mixing of mineral-rich, advecting hydrothermal fluids with bottom seawater; (2) similar deposits at inactive hydrothermal vent sites, where fluid advection has ceased but mineral deposits remain; (3) polymetallic nodules that form on the seafloor of the open ocean

Midwater ecosystems must be considered when evaluating environmental risks of deep-sea mining

“…The mesopelagic zone is the natural entry point for mercury into oceanic food webs and the human seafood supply (27), raising concerns that discharge of metals and toxins into the mesopelagic zone could contaminate seafood. The structure and function of microbial communities currently regenerating essential nutrients for the pelagic ecosystem may shift as a consequence of enhanced particle surface areas (28).…”

Climate change considerations are fundamental to management of deep‐sea resource extraction

“…Trawling or mining may disrupt dark (non-photosynthetic) carbon fixation associated with deep-sea water, sediments, or nodules (Sweetman et al, 2019), with consequences for local carbon cycling (Orcutt et al, 2020).…”

“…Nevertheless, abyssal disturbance-induced remineralization is unlikely to influence atmospheric CO 2 concentrations in the near future given the low concentration and refractory nature of carbon in sediments (Orcutt et al, 2020) and millennial time scales of carbon cycling at those depths (Atwood et al, 2020).…”

“…we feel it is premature to predict if and how they will include this. Maintaining ecosystem integrity will also critically require understanding microbial responses to climate change in tandem with physical disturbance (Orcutt et al, 2020). Multi-omics offers potential to assess functional diversity (Ansorge et al, 2019) and microbiological control on greenhouse gases (Birrer et al, 2019).…”

Microbial Diversity of Deep-Sea Ferromanganese Crust Field in the Rio Grande Rise, Southwestern Atlantic Ocean

“…Despite the increasing efforts that have been made using high-throughput DNA sequencing of microbes living on Fe-Mn crusts from the Pacific Ocean, similar studies from the Atlantic Ocean are still scarce. Considering the wide distribution of Fe-Mn crusts on seamounts globally and their potential for future mineral resource supplies [10], the study of their microbiome, function and resilience to environmental impacts caused by its exploitation is essential [33].…”