Abstract
Polymetallic nodule mining at abyssal depths in the Clarion Clipperton Fracture Zone (Eastern Central Pacific) will impact one of the most remote and least known environments on Earth. Since vast areas are being targeted by concession holders for future mining, large-scale effects of these activities are expected. Hence, insight into the fauna associated with nodules is crucial to support effective environmental management. In this study video surveys were used to compare the epifauna from sites with contrasting nodule coverage in four license areas. Results showed that epifaunal densities are more than two times higher at dense nodule coverage (>25 versus ≤10 individuals per 100 m2), and that taxa such as alcyonacean and antipatharian corals are virtually absent from nodule-free areas. Furthermore, surveys conducted along tracks from trawling or experimental mining simulations up to 37 years old, suggest that the removal of epifauna is almost complete and that its full recovery is slow. By highlighting the importance of nodules for the epifaunal biodiversity of this abyssal area, we urge for cautious consideration of the criteria for determining future preservation zones.
Highlights
Morphological and molecular analyses are currently being conducted on voucher specimens collected during the Remote Operated Vehicle (ROV) dives to validate video observations as well as to determine true species diversity and population connectivity
Alcyonacea, Antipatharia, Actiniaria and Porifera were represented by several morphotypes, many of which were growing on nodules (Fig. 4)
This study provides evidence that high densities of surface nodules in the preservation reference zones (PRZ) is an ultimate requirement for the preservation of abyssal biodiversity within the CCZ
Summary
Sessile metazoan epifauna on nodule transects comprised 8 major groups, representing Hydrozoa, Anthozoa (Actiniaria, Alcyonacea, Antipatharia, Corallimorpharia, Ceriantharia), Echinodermata (Crinoidea) and Porifera (Hexactinellida). In comparison to nodule fields in the central CCZ, all four video transects performed in the area surveyed at the center of APEI no #3, which is nodule-rich, showed low densities of both sessile (2–5 ind./100 m2) and mobile fauna (
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