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

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.