Toward a reliable assessment of potential ecological impacts of deep‐sea polymetallic nodule mining on abyssal infauna

Lidia Lins,Daniela Zeppilli,Ellen Pape,Miriam Brandt,Stefanie Kaiser,Chisato Murakami,Pedro Martínez Arbizu,Lénaïck Menot,Joan M Alfaro‐Lucas,Paulo Bonifácio,Ann Vanreusel,Lara Macheriotou,Tania Nara Bezerra,Sven Rossel,Loïc N Michel,Nuria Sánchez,Katja Uhlenkott

doi:10.1002/lom3.10448

Abstract

AbstractThe increasing demand for metals is pushing forward the progress of deep‐sea mining industry. The abyss between the Clarion and Clipperton Fracture Zones (CCFZ), a region holding a higher concentration of minerals than land deposits, is the most targeted area for the exploration of polymetallic nodules worldwide, which may likely disturb the seafloor across large areas and over many years. Effects from nodule extraction cause acute biodiversity loss of organisms inhabiting sediments and polymetallic nodules. Attention to deep‐sea ecosystems and their services has to be considered before mining starts but the lack of basic scientific knowledge on the methodologies for the ecological surveys of fauna in the context of deep‐sea mining impacts is still scarce. We review the methodology to sample, process and investigate metazoan infauna both inhabiting sediments and nodules dwelling on these polymetallic‐nodule areas. We suggest effective procedures for sampling designs, devices and methods involving gear types, sediment processing, morphological and genetic identification including metabarcoding and proteomic fingerprinting, the assessment of biomass, functional traits, fatty acids, and stable isotope studies within the CCFZ based on both first‐hand experiences and literature. We recommend multi‐ and boxcorers for the quantitative assessments of meio‐ and macrofauna, respectively. The assessment of biodiversity at species level should be focused and/or the combination of morphological with metabarcoding or proteomic fingerprinting techniques. We highlight that biomass, functional traits, and trophic markers may provide critical insights for biodiversity assessments and how statistical modeling facilitates predicting patterns spatially across point‐source data and is essential for conservation management.

Highlights

We review and suggest efficient procedures for sampling design, devices and methods including gears, sediment slicing and sieving, morphological and genetic identification, isotope and biomass studies, assessment of functional traits, as well as biodiversity assessment using metabarcoding and proteomic fingerprinting
The Clarion– Clipperton Fracture Zone (CCFZ) is a large area with 6 million km2 laying between 4000 and 5500 m depth within the central Pacific Ocean with polymetallic nodule fields occurring as patches (Wedding et al 2015; Kuhn et al 2017; Glover et al 2018)
Jumars (1981) summarized the impacts on the benthic fauna derived from mining activities as follows: (1) direct mechanical impacts along the track of the nodule collector where the sediment and associated fauna are crushed or dispersed in a plume; the nodules are removed and the sediment is compacted by the nodule collector, (2) burial of benthic fauna by the sediment plume, and (3) alteration of food resources and changes in biochemical conditions caused by the removal of the top sediment layers

Summary

Introduction

We review and suggest efficient procedures for sampling design, devices and methods including gears, sediment slicing and sieving, morphological and genetic identification, isotope and biomass studies, assessment of functional traits, as well as biodiversity assessment using metabarcoding and proteomic fingerprinting. In order to be inclusive of the potential size range of meiofaunal taxa, we recommend here to not use an upper sieve when processing meiofauna samples.

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