Benthic Communities on the Mohn’s Treasure Mound: Implications for Management of Seabed Mining in the Arctic Mid-Ocean Ridge

Eva Ramirez-Llodra,Torkild Bakken,Ana Hilario,Emil Paulsen,Geir Johnsen,Hans Tore Rapp,Carolina Ventura Costa

doi:10.3389/fmars.2020.00490

Abstract

The Mohn’s Treasure, described as an inactive sulphide mound, was discovered at 2600 m depth on the Arctic Mid-Ocean Ridge in 2002. In 2015, we conducted the first biological survey of Mohn’s Treasure using ROV photo transects and sampling. This site is covered by a thick layer of fine sediments, where hard substratum is only visible as rocky outcrops on ridges. The observed benthic community was typical of Arctic bathyal systems. A total of 46 species (identified as morphospecies) were recorded, with densities varying from 12.2 to 31.6 ind.m-2. The two most abundant phyla were Porifera and Echinodermata. The sediment is dominated by fields of the stalked crinoid Bathycrinus carpenterii, while areas of hard substratum were characterised by high abundances of several sponge species and associated fauna. Interest in commercial exploration and exploitation of minerals from massive sulphide deposits is rising globally, and the Arctic Mid-Ocean Ridge is being targeted for mineral exploration within Norwegian waters. Gathering baseline ecological data from these poorly known sites is thus urgent and essential if robust resource management measures are to be developed and implemented. The results of this ecological survey are discussed in relation to the designation of deep-sea Vulnerable Marine Ecosystems and their implication in management and conservation of areas targeted by the emerging deep-sea mining industry.

Highlights

Since hydrothermal vents were discovered in 1977, scientific research has been the primary source of anthropogenic disturbance in these ecosystems
The aim of this study was to provide the first biological data of the region by assessing the faunal composition, community structure, and biodiversity of the megabenthic community to provide initial baseline information that can inform management measures related to seabed mining in the Arctic Mid-Ocean Ridge (AMOR) region
Mohn’s Treasure has been described as a massive sulfide deposit, the only evidence of mineralization found during the entire MarMine survey over the area (13 remotely operated vehicle (ROV) dives) was a few meters of oxidized basalt outcrops comprising minor pyrites and features possibly formed by diffuse discharges (Ludvigsen et al, 2016)

Summary

Introduction

Since hydrothermal vents were discovered in 1977, scientific research has been the primary source of anthropogenic disturbance in these ecosystems. SMS are large deposits of polymetallicbearing sulfides on and below the seabed, formed through precipitation of metals contained in the hydrothermal fluids emanating from active vents. SMS deposits can be found associated to active vents, as well as at inactive ones, where fluid flow has stopped, and the chemosynthetic-based faunal communities have disappeared (Van Dover, 2019). Large biomass of highly adapted organisms is sustained by the primary production of chemoautotrophic microorganisms, both free-living and in symbiosis with the fauna (Van Dover, 2010). Mining SMS deposits represents a whole new level of impact on these unique and rare vent ecosystems (Van Dover et al, 2018), and a better understanding of the community composition, ecosystem function, and population connectivity is essential for the development of sound environmental management, conservation measures, and decision making

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Methods

Conclusion