Identifying Toxic Impacts of Metals Potentially Released during Deep-Sea Mining—A Synthesis of the Challenges to Quantifying Risk

Abstract

In January 2017, the International Seabed Authority released a discussion paper on the development of Environmental Regulations for deep-sea mining (DSM) within the Area Beyond National Jurisdiction (the "Area"). With the release of this paper, the prospect for commercial mining in the Area within the next decade has become very real. Moreover, within nations' Exclusive Economic Zones, the exploitation of deep-sea mineral ore resources could take place on very much shorter time scales and, indeed, may have already started. However, potentially toxic metal mixtures may be released at sea during different stages of the mining process and in different physical phases (dissolved or particulate). As toxicants, metals can disrupt organism physiology and performance, and therefore may impact whole populations, leading to ecosystem scale effects. A challenge to the prediction of toxicity is that deep-sea ore deposits include complex mixtures of minerals, including potentially toxic metals such as copper, cadmium, zinc, and lead, as well as rare earth elements. Whereas the individual toxicity of some of these dissolved metals has been established in laboratory studies, the complex and variable mineral composition of seabed resources makes the a priori prediction of the toxic risk of DSM extremely challenging. Furthermore, although extensive data quantify the toxicity of metals in solution in shallow-water organisms, these may not be representative of the toxicity in deep-sea organisms, which may differ biochemically and physiologically and which will experience those toxicants under conditions of low temperature, high hydrostatic pressure, and potentially altered pH. In this synthesis, we present a summation of recent advances in our understanding of the potential toxic impacts of metal exposure to deep-sea meio-to megafauna at low temperature and high pressure, and consider the limitation of deriving lethal limits based on the paradigm Hauton et al.Identifying Toxic Impacts of Deep-Sea Mining of exposure to single metals in solution. We consider the potential for long-term and farfield impacts to key benthic invertebrates, including the very real prospect of sub-lethal impacts and behavioral perturbation of exposed species. In conclusion, we advocate the adoption of an existing practical framework for characterizing bulk resource toxicity in advance of exploitation.

Lifecycle Ecology of Deep-Sea Chemosymbiotic Mussels: A Review

“…Beyond the visible impacts that human activities can have on adult bathymodiolins and other fauna living within established benthic communities, the consequences for the remainder of their lifecycle are far more difficult to evaluate. Although the physico-chemical stimuli that trigger larval settlement in Bathymodiolinae remain speculative, early developmental phases may be acutely sensitive to additional anthropogenic sources of physiological stress, including the release of toxic compounds, increasing turbidity, or potentially misleading physical and chemical cues (Hauton et al, 2017).…”

“…In both oil and mineral extraction, habitat destruction and the resuspension of both sediment and potentially toxic chemical compounds during operations that require drilling or cutting (e.g., copper and other metals or lubricating organics, see Hauton et al, 2017) may prove highly deleterious for local and regional benthic communities. Resuspended sediment loading may smother many sessile organisms including Bathymodolinae, in the immediate vicinity of mining activity.…”

Ethics to Intersect Civic Participation and Formal Guidance

“…Compared to many terrestrial environments, the marine environments are technologically challenging; winds and waves, or corrosion, come to mind. Although the conditions at the seabed (pressure, temperature) are harsh, the primary technological challenge is to combine remotely controlled mobile operations at the seabed with operation in the water column and at the sea surface [56][57][58][59][60]. Beyond causing heavy corrosion of the equipment, the chemical properties of water facilitate solution and suspension of liquids of different nature.…”

Responses of an abyssal meiobenthic community to short-term burial with crushed nodule particles in the south-east Pacific

“…Mevenkamp et al: Crushed nodule particle experiment in the south-east Pacific velopments have led to a new surge in deep-sea minerals in the past decade, and legal frameworks are being developed to manage their exploitation in international waters (Lodge et al, 2014). Polymetallic nodules are decimetre-sized concretions of ore lying on the surface of abyssal sediments in 4000-6500 m water depth and cover large areas of the Pacific and Indian Ocean (Hein and Koschinsky, 2014). Besides the high content in valuable metals such as copper, nickel and cobalt, polymetallic nodules exhibit a high porosity, low bulk density and fine grain size, with very slow formation and growth rates of 5 to 250 mm Myr −1 (million years) (Von Stackelberg, 2000;Hein et al, 2013).…”

“…Another possible risk of polymetallic nodule mining is the release of potentially toxic amounts of heavy metals during sediment resuspension and nodule abrasion, with largely unknown effects on deep-sea biota (Hauton et al, 2017). Bioavailability and toxicity of metals inside marine sediments strongly depend on the structure and chemical properties of the sediment, and these complex processes are not yet fully understood (Eggleton and Thomas, 2004).…”