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Megafaunal variation in the abyssal landscape of the Clarion Clipperton Zone

Megafaunal variation in the abyssal landscape of the Clarion Clipperton Zone
Megafaunal variation in the abyssal landscape of the Clarion Clipperton Zone

The potential for imminent polymetallic nodule mining in the Clarion Clipperton Fracture Zone (CCZ) has attracted considerable scientific and public attention. This concern stems from both the extremely large seafloor areas that may be impacted by mining, and the very limited knowledge of the fauna and ecology of this region. The environmental factors regulating seafloor ecology are still very poorly understood. In this study, we focus on megafaunal ecology in the proposed conservation zone ‘Area of Particular Environmental Interest 6′ (study area centred 17°16′N, 122°55′W). We employ bathymetric data to objectively define three landscape types in the area (a level bottom Flat, an elevated Ridge, a depressed Trough; water depth 3950–4250 m) that are characteristic of the wider CCZ. We use direct seabed sampling to characterise the sedimentary environment in each landscape, detecting no statistically significant differences in particle size distributions or organic matter content. Additional seafloor characteristics and data on both the metazoan and xenophyophore components of the megafauna were derived by extensive photographic survey from an autonomous underwater vehicle. Image data revealed that there were statistically significant differences in seafloor cover by nodules and in the occurrence of other hard substrata habitat between landscapes. Statistically significant differences in megafauna standing stock, functional structuring, diversity, and faunal composition were detected between landscapes. The Flat and Ridge areas exhibited a significantly higher standing stock and a distinct assemblage composition compared to the Trough. Geomorphological variations, presumably regulating local bottom water flows and the occurrence of nodule and xenophyophore test substrata, between study areas may be the mechanism driving these assemblage differences. We also used these data to assess the influence of sampling unit size on the estimation of ecological parameters. We discuss these results in the contexts of regional benthic ecology and the appropriate management of potential mining activities in the CCZ and elsewhere in the deep ocean.

Abyssal plains, APEI, Biodiversity, CCZ, Deep-sea mining, Geomorphology, NE Pacific, Polymetallic nodules, Sample size
0079-6611
119-133
Simon-Lledó, Erik
80f67b3a-44e7-466e-aed5-06b0ba788ca2
Bett, Brian J.
61342990-13be-45ae-9f5c-9540114335d9
Huvenne, Veerle A.I.
f22be3e2-708c-491b-b985-a438470fa053
Schoening, Timm
76c160ff-472f-41bb-ba72-ba7388fde000
Benoist, Noelie M.A.
9a06e349-0049-49dc-a616-97c43d222a2e
Jeffreys, Rachel M.
00be4640-1d07-4f82-964a-0a61b50322c4
Durden, Jennifer M.
d7101246-b76b-44bc-8956-8ca4ae62ae1f
Jones, Daniel O.B.
44fc07b3-5fb7-4bf5-9cec-78c78022613a
Simon-Lledó, Erik
80f67b3a-44e7-466e-aed5-06b0ba788ca2
Bett, Brian J.
61342990-13be-45ae-9f5c-9540114335d9
Huvenne, Veerle A.I.
f22be3e2-708c-491b-b985-a438470fa053
Schoening, Timm
76c160ff-472f-41bb-ba72-ba7388fde000
Benoist, Noelie M.A.
9a06e349-0049-49dc-a616-97c43d222a2e
Jeffreys, Rachel M.
00be4640-1d07-4f82-964a-0a61b50322c4
Durden, Jennifer M.
d7101246-b76b-44bc-8956-8ca4ae62ae1f
Jones, Daniel O.B.
44fc07b3-5fb7-4bf5-9cec-78c78022613a

Simon-Lledó, Erik, Bett, Brian J., Huvenne, Veerle A.I., Schoening, Timm, Benoist, Noelie M.A., Jeffreys, Rachel M., Durden, Jennifer M. and Jones, Daniel O.B. (2019) Megafaunal variation in the abyssal landscape of the Clarion Clipperton Zone. Progress in Oceanography, 170, 119-133. (doi:10.1016/j.pocean.2018.11.003).

Record type: Article

Abstract

The potential for imminent polymetallic nodule mining in the Clarion Clipperton Fracture Zone (CCZ) has attracted considerable scientific and public attention. This concern stems from both the extremely large seafloor areas that may be impacted by mining, and the very limited knowledge of the fauna and ecology of this region. The environmental factors regulating seafloor ecology are still very poorly understood. In this study, we focus on megafaunal ecology in the proposed conservation zone ‘Area of Particular Environmental Interest 6′ (study area centred 17°16′N, 122°55′W). We employ bathymetric data to objectively define three landscape types in the area (a level bottom Flat, an elevated Ridge, a depressed Trough; water depth 3950–4250 m) that are characteristic of the wider CCZ. We use direct seabed sampling to characterise the sedimentary environment in each landscape, detecting no statistically significant differences in particle size distributions or organic matter content. Additional seafloor characteristics and data on both the metazoan and xenophyophore components of the megafauna were derived by extensive photographic survey from an autonomous underwater vehicle. Image data revealed that there were statistically significant differences in seafloor cover by nodules and in the occurrence of other hard substrata habitat between landscapes. Statistically significant differences in megafauna standing stock, functional structuring, diversity, and faunal composition were detected between landscapes. The Flat and Ridge areas exhibited a significantly higher standing stock and a distinct assemblage composition compared to the Trough. Geomorphological variations, presumably regulating local bottom water flows and the occurrence of nodule and xenophyophore test substrata, between study areas may be the mechanism driving these assemblage differences. We also used these data to assess the influence of sampling unit size on the estimation of ecological parameters. We discuss these results in the contexts of regional benthic ecology and the appropriate management of potential mining activities in the CCZ and elsewhere in the deep ocean.

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Accepted/In Press date: 15 November 2018
e-pub ahead of print date: 16 November 2018
Published date: 1 January 2019
Keywords: Abyssal plains, APEI, Biodiversity, CCZ, Deep-sea mining, Geomorphology, NE Pacific, Polymetallic nodules, Sample size

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Local EPrints ID: 426939
URI: http://eprints.soton.ac.uk/id/eprint/426939
ISSN: 0079-6611
PURE UUID: c9b06f55-7bf0-4b04-b6bd-05a028b2a73b
ORCID for Veerle A.I. Huvenne: ORCID iD orcid.org/0000-0001-7135-6360
ORCID for Noelie M.A. Benoist: ORCID iD orcid.org/0000-0003-1978-3538

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Date deposited: 18 Dec 2018 17:30
Last modified: 07 Oct 2020 02:11

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Contributors

Author: Erik Simon-Lledó
Author: Brian J. Bett
Author: Veerle A.I. Huvenne ORCID iD
Author: Timm Schoening
Author: Noelie M.A. Benoist ORCID iD
Author: Rachel M. Jeffreys
Author: Jennifer M. Durden
Author: Daniel O.B. Jones

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