Environmental Heterogeneity Throughout the Clarion-Clipperton Zone and the Potential Representativity of the APEI Network

Travis W Washburn,Craig R Smith,Chih-Lin Wei,Daniel O B Jones

doi:10.3389/fmars.2021.661685

Abstract

Environmental variables such as food supply, nodule abundance, sediment characteristics, and water chemistry may influence abyssal seafloor communities and ecosystem functions at scales from meters to thousands of kilometers. Thus, knowledge of environmental variables is necessary to understand drivers of organismal distributions and community structure, and for selection of proxies for regional variations in community structure, biodiversity, and ecosystem functions. In October 2019, the Deep CCZ Biodiversity Synthesis Workshop was conducted to (i) compile recent seafloor ecosystem data from the Clarion-Clipperton Zone (CCZ), (ii) synthesize patterns of seafloor biodiversity, ecosystem functions, and potential environmental drivers across the CCZ, and (iii) assess the representativity of no-mining areas (Areas of Particular Environmental Interest, APEIs) for subregions and areas in the CCZ targeted for polymetallic nodule mining. Here we provide a compilation and summary of water column and seafloor environmental data throughout the CCZ used in the Synthesis Workshop and in many of the papers in this special volume. Bottom-water variables were relatively homogenous throughout the region while nodule abundance, sediment characteristics, seafloor topography, and particulate organic carbon flux varied across CCZ subregions and between some individual subregions and their corresponding APEIs. This suggests that additional APEIs may be needed to protect the full range of habitats and biodiversity within the CCZ.

Highlights

Environmental Conditions in the Deep SeaContrary to popular perception, the abyssal seafloor exhibits substantial variability in habitat structure and key environmental variables across a broad range of scales, with corresponding heterogeneity in benthic habitat structure and biodiversity (e.g., Lutz et al, 2007; Wei et al, 2010; Danovaro et al, 2014; Zeppilli et al, 2016; Smith et al, 2020)
The Areas of Particular Environmental Interest (APEIs) network was originally designed to protect the full range of deep-sea habitats in the Clipperton Fracture Zones (CCZ), capturing differences in seafloor community structure and function driven by food availability, nodule abundance, and the occurrence of seamounts (ISA, 2008; Wedding et al, 2013)
Reserve areas, and APEIs were obtained from the International Seabed Authority (ISA),1 while the locations of the nine environmental subregions used in recommending APEI locations were obtained from Wedding et al (2013) (Figure 1)

Summary

Introduction

Environmental Conditions in the Deep SeaContrary to popular perception, the abyssal seafloor exhibits substantial variability in habitat structure and key environmental variables across a broad range of scales, with corresponding heterogeneity in benthic habitat structure and biodiversity (e.g., Lutz et al, 2007; Wei et al, 2010; Danovaro et al, 2014; Zeppilli et al, 2016; Smith et al, 2020). To predict and manage the impacts of human activities in the deep sea, detailed understanding of baseline ecosystem conditions is essential. This requires assessment of the natural variability of environmental drivers and biological communities in space and time. Polymetallic nodule areas of greatest economic interest occur in the Pacific Ocean, between the CCZ (Hein et al, 2013). To protect regional biodiversity and ecosystem functions in the face of nodule mining, a system of nine “no-mining” areas, called Areas of Particular Environmental Interest (APEIs) have been established within the CCZ region. The APEI network was originally designed to protect the full range of deep-sea habitats in the CCZ, capturing differences in seafloor community structure and function driven by food availability (e.g., north-south and east-west gradients in seafloor particulate organic carbon flux), nodule abundance, and the occurrence of seamounts (ISA, 2008; Wedding et al, 2013)

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Discussion

Conclusion