Are shallow-water shrimps proxies for hydrothermal-vent shrimps to assess the impact of deep-sea mining?

Integrated transcriptomic and metabolomic approaches reveal molecular response and potential biomarkers of the deep-sea mussel Gigantidas platifrons to copper exposure

Metal pollution caused by deep-sea mining activities has potential detrimental effects on deep-sea ecosystems. However, our knowledge of how deep-sea organisms respond to this pollution is limited, given the challenges of remoteness and technology. To address this, we conducted a toxicity experiment by using deep-sea mussel Gigantidas platifrons as model animals and exposing them to different copper (Cu) concentrations (50 and 500 μg/L) for 7 days. Transcriptomics and LC-MS-based metabolomics methods were employed to characterize the profiles of transcription and metabolism in deep-sea mussels exposed to Cu. Transcriptomic results suggested that Cu toxicity significantly affected the immune response, apoptosis, and signaling processes in G. platifrons. Metabolomic results demonstrated that Cu exposure disrupted its carbohydrate metabolism, anaerobic metabolism and amino acid metabolism. By integrating both sets of results, transcriptomic and metabolomic, we find that Cu exposure significantly disrupts the metabolic pathway of protein digestion and absorption in G. platifrons. Furthermore, several key genes (e.g., heat shock protein 70 and baculoviral IAP repeat-containing protein 2/3) and metabolites (e.g., alanine and succinate) were identified as potential molecular biomarkers for deep-sea mussel's responses to Cu toxicity. This study contributes novel insight for assessing the potential effects of deep-sea mining activities on deep-sea organisms.

Toxicology assessment of deep-sea mining impacts on Gigantidas platifrons: A comparative in situ and laboratory metal exposure study

Deep-sea toxicology is essential for deep-sea environmental impact assessment. Yet most toxicology experiments are conducted solely in laboratory settings, overlooking the complexities of the deep-sea environment. Here we carried out metal exposure experiments in both the laboratory and in situ, to compare and evaluate the response patterns of Gigantidas platifrons to metal exposure (copper [Cu] or cadmium [Cd] at 100 μg/L for 48 h). Metal concentrations, traditional biochemical parameters, and fatty acid composition were assessed in deep-sea mussel gills. The results revealed significant metal accumulation in deep-sea mussel gills in both laboratory and in situ experiments. Metal exposure could induce oxidative stress, neurotoxicity, an immune response, altered energy metabolism, and changes to fatty acid composition in mussel gills. Interestingly, the metal accumulating capability, biochemical response patterns, and fatty acid composition each varied under differing experimental systems. In the laboratory setting, Cd-exposed mussels exhibited a higher value for integrated biomarker response (IBR) while in situ the Cu-exposed mussels instead displayed a higher IBR value. This study emphasizes the importance of performing deep-sea toxicology experiments in situ and contributes valuable data to a standardized workflow for deep-sea toxicology assessment.

Stressors of emerging concern in deep-sea environments: microplastics, pharmaceuticals, personal care products and deep-sea mining

Although most deep-sea areas are remote in comparison to coastal zones, a growing body of literature indicates that many sensitive ecosystems could be under increased stress from anthropogenic sources. Among the multiple potential stressors, microplastics (MPs), pharmaceuticals and personal care products (PPCPs/PCPs) and the imminent start of commercial deep-sea mining have received increased attention. Here we review recent literature on these emerging stressors in deep-sea environments and discuss cumulative effects with climate change associated variables. Importantly, MPs and PPCPs have been detected in deep-sea waters, organisms and sediments, in some locations in comparable levels to coastal areas. The Atlantic Ocean and the Mediterranean Sea are the most studied areas and where higher levels of MPs and PPCPs have been detected. The paucity of data for most other deep-sea ecosystems indicates that many more locations are likely to be contaminated by these emerging stressors, but the absence of studies hampers a better assessment of the potential risk. The main knowledge gaps in the field are identified and discussed, and future research priorities are highlighted to improve hazard and risk assessment.

A modelling framework to assess multiple metals impacts on marine food webs: Relevance for assessing the ecological implications of deep-sea mining based on a systematic review

Industrial deep-sea mining will release plumes containing metals that may disperse over long distances; however, there is no general understanding of metal effects on marine ecosystems. Thus, we conducted a systematic review in search of models of metal effects on aquatic biota with the future perspective to support Environmental Risk Assessment (ERA) of deep-sea mining. According to results, the use of models to study metal effects is strongly biased towards freshwater species (83% freshwater versus 14% marine); Cu, Hg, Al, Ni, Pb, Cd and Zn are the best-studied metals, and most studies target few species rather than entire food webs. We argue that these limitations restrain ERA on marine ecosystems. To overcome this gap of knowledge, we suggest future research directions and propose a modelling framework to predict the effects of metals on marine food webs, which in our view is relevant for ERA of deep-sea mining.

Deep seabed mining and communities: A transdisciplinary approach to ecological risk assessment in the South Pacific

Deep-sea mineral extraction is a fledgling industry whose guiding principles, legislation, protocols, and regulations are still evolving. Responsible management of the industry is difficult when it is not clearly understood what biological and environmental diversity or ecosystem services may be at risk. But the industry's infancy provides an opportunity to address this challenge by stakeholder-led development and implementation of a multidisciplinary risk assessment framework. This article aims to present the findings of a workshop held in New Zealand that hosted stakeholders from a broad range of interests and regions in the South Pacific associated with the deep-sea mineral activity. The outputs provide stakeholder-informed ecological risk assessment approaches for deep-sea mining activities, identifying tools and techniques to improve the relevance of risk assessment of deep seabed mining projects to communities in the South Pacific. Discussions highlighted the importance of trust or respect among stakeholders, valuing the "life force" of the ocean, the importance of scientific data, and the complications associated with defining acceptable change. This research highlighted the need for a holistic transdisciplinary approach that connects science, management, industry, and community, an approach most likely to provide a "social license" to operate. There is also a need to revise traditional risk assessment methods to make them more relevant to stakeholders. The development of ecotoxicological tools and approaches is an example of how existing practices could be improved to better support deep-sea mineral management. A case study is provided that highlights the current challenges within the legislative framework of New Zealand. Integr Environ Assess Manag 2022;18:664-673. © 2021 SETAC.

Copper-binding ligands in deep-sea pore waters of the Pacific Ocean and potential impacts of polymetallic nodule mining on the copper cycle

The release of potentially toxic metals, such as copper (Cu), into the water column is of concern during polymetallic nodule mining. The bioavailability and thus toxicity of Cu is strongly influenced by its speciation which is dominated by organic ligand (L) complexation in seawater, with L-complexes being considered less bioavailable than free Cu²⁺. The presence of CuL-complexes in deep-sea sediments has, however, not been systematically studied in the context of deep-sea mining. We thus analyzed the Cu-binding L concentration ([L]) in deep-sea pore waters of two polymetallic nodule provinces in the Pacific Ocean, the Peru Basin and the Clarion-Clipperton-Zone, using competitive ligand equilibration–adsorptive stripping voltammetry. The pore-water dissolved Cu concentration ([dCu]) ranged from 3 to 96 nM, generally exceeding bottom water concentrations (4–44 nM). Based on fitting results from ProMCC and Excel, Cu was predominantly complexed by L (3–313 nM) in bottom waters and undisturbed pore waters. We conclude that processes like deep-sea mining are unlikely to cause a release of toxic Cu²⁺ concentrations ([Cu²⁺]) to the seawater as > 99% Cu was organically complexed in pore waters and the [Cu²⁺] was < 6 pM for 8 of 9 samples. Moreover, the excess of L found especially in shallow pore waters implied that even with a Cu release through mining activities, Cu²⁺ likely remains beneath toxic thresholds.

Comparative Proteomics on Deep-Sea Amphipods after in Situ Copper Exposure

The interest in deep-sea mining increased along with the environmental concerns of these activities to the deep-sea fauna. The discovery of optimal biomarkers of deep-sea mining activities in deep-sea species is a crucial step toward the supply of important ecological information for environmental impact assessment. In this study, an in situ copper exposure experiment was performed on deep-sea scavenging amphipods. Abyssorchomene distinctus individuals were selected among all the exposed amphipods for molecular characterization. Copper concentration within the gut was assessed, followed by a tandem mass tag-based coupled with two-dimensional liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) applied to identify and quantify the protein expression changes after 48 h of exposure. 2937 proteins were identified and annotated, and 1918 proteins among all identified proteins were assigned by at least two nonambiguous peptides. The screening process was performed based on the differences in protein abundance and the specific correlation between the proteins and copper in previous studies. These differentially produced proteins include Na⁺/K⁺ ATPase, cuticle, chitinase, and proteins with unknown function. Their abundances showed correlation with copper and had high sensitivity to indicate the copper level, being here proposed as biomarker candidates for deep-sea mining activities in the future. This is a key step in the development of environmental impact assessment of deep-sea mining activities integrating ecotoxicological data.