Geomorphological evidence of large vertebrates interacting with the seafloor at abyssal depths in a region designated for deep-sea mining.

Leigh Marsh,Daniel O B Jones,Veerle A I Huvenne

doi:10.1098/rsos.180286

Leigh Marsh, Daniel O B Jones + Show 1 more

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https://doi.org/10.1098/rsos.180286

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Abstract

Exploration licences for seafloor mineral deposits have been granted across large areas of the world's oceans, with the abyssal Pacific Ocean being the primary target for polymetallic nodules—a potentially valuable source of minerals. These nodule-bearing areas support a large diversity of deep-sea life and although studies have begun to characterize the benthic fauna within the region, the ecological interactions between large bathypelagic vertebrates of the open ocean and the abyssal seafloor remain largely unknown. Here we report seafloor geomorphological alterations observed by an autonomous underwater vehicle that suggest large vertebrates could have interacted with the seafloor to a maximum depth of 4258 m in the recent geological past. Patterns of disturbance on the seafloor are broadly comparable to those recorded in other regions of the world's oceans attributed to beaked whales. These observations have important implications for baseline ecological assessments and the environmental management of potential future mining activities within this region of the Pacific.

Highlights

The abyssal seafloor represents approximately 85% of the global seafloor [1], yet many of the ecosystems and species that it sustains are largely unknown because of the difficulties in studying such a vast and remote environment
We demonstrate that sequential depressions represented by acoustic shadows from autonomous underwater vehicle (AUV) geophysical surveys observed in the Clarion–Clipperton Zone (CCZ) are spatially comparable and, from limited seafloor imagery, represent a morphology akin to those inferred from beaked whales in the Atlantic [10] and Mediterranean [11,12]
Depressions consisted of irregular furrows on the seafloor approximately 0.13 m deep

Summary

Introduction

The abyssal seafloor represents approximately 85% of the global seafloor [1], yet many of the ecosystems and species that it sustains are largely unknown because of the difficulties in studying such a vast and remote environment. We demonstrate that sequential depressions represented by acoustic shadows from autonomous underwater vehicle (AUV) geophysical surveys observed in the CCZ are spatially comparable and, from limited seafloor imagery, represent a morphology akin to those inferred from beaked whales in the Atlantic [10] and Mediterranean [11,12].

Results

Conclusion