Biogeography and community structure of abyssal scavenging Amphipoda (Crustacea) in the Pacific Ocean

Tasnim Patel,Koen Martens,Henri Robert,Ilse De Mesel,Steven Degraer,Isa Schön,Cedric D'Udekem D'Acoz

doi:10.5194/bg-17-2731-2020

Abstract

Abstract. In 2015, we collected more than 60 000 scavenging amphipod specimens during two expeditions to the Clarion–Clipperton fracture zone (CCZ) in the Northeast (NE) Pacific and to the DISturbance and re-COLonisation (DisCOL) experimental area (DEA), a simulated mining impact disturbance proxy in the Peru Basin in the Southeast (SE) Pacific. Here, we compare biodiversity patterns of the larger specimens (>15 mm) within and between these two oceanic basins. Eight scavenging amphipod species are shared between these two areas, thus indicating connectivity. Overall diversity was lower in the DEA (Simpson index, D = 0.62), when compared to the CCZ (D=0.73), and particularly low at the disturbance site in the DEA and the site geographically closest to it. Local differences within each basin were observed too. The community compositions of the two basins differ, as evidenced by a non-metric dimensional scaling (NMDS) analysis of beta biodiversity. Finally, a single species, Abyssorchomene gerulicorbis (Schulenberger and Barnard, 1976), dominates the DEA with 60 % of all individuals.

Highlights

The abyssal deep sea (3000–6000 m) represents the largest ecosystem on the planet, with the abyssal seafloor covering approximately 54 % of the Earth’s solid surface (Gage and Tyler, 1991; Rex et al, 1993)
We investigated the amphipod communities of two oceanic basins (Fig. 1): (i) the Clarion–Clipperton fracture zone (CCZ, 6 × 102 km2, 7000 km wide), an economically important manganese nodule field in the NE Pacific, comprising several different contractor licence areas, and nine designated Areas of Particular Ecological Interest (APEIs) as designated by the International Seabed Authority (ISA) (Lodge et al, 2014), and (ii) the DISturbance and re-COLonisation (DisCOL) experimental area (DEA, 11 km2, 4 km wide), a mining disturbance proxy in the Peru Basin in the SE Pacific
The 2984 individuals from the DEA represent 15 morphotypes. Six of these have been identified to the species level: Abyssorchomene distinctus (Birstein and Vinogradov, 1960), Abyssorchomene gerulicorbis (Schulenberger and Barnard, 1976), Eurythenes sigmiferus (d’Udekem d’Acoz and Havermans, 2015), Paralicella caperesca (Schulenberger and Barnard, 1976), Parandaniexis mirabilis Schellenberg, 1929, and Tectovalopsis regelatus Barnard and Ingram, 1990

Summary

Introduction

The abyssal deep sea (3000–6000 m) represents the largest ecosystem on the planet, with the abyssal seafloor covering approximately 54 % of the Earth’s solid surface (Gage and Tyler, 1991; Rex et al, 1993) Since it is one of the least investigated ecosystems, there are still extensive gaps in our knowledge of deep-sea fauna (German et al, 2011). Marine research has far focused on coastal areas, hydrothermal vents or chemosynthetic habitats, whereas openocean abyssal plains have been less extensively investigated (Ramirez-Llodra et al, 2010) This is unsurprising given the challenges of sampling this remote environment, which is impeded by several confounding factors. Owing to the low availability of data about deepsea biodiversity, combined with the inherent risk of undersampling, it is difficult to estimate species richness in the deep sea

Methods

Results

Discussion

Conclusion