I. Introduction
Half our planet is covered by deep ocean more than 3000m deep and most of it remains unexplored. For example, the South Pacific basin represents Earth's largest deep ocean basin and the largest contiguous ecosystem for life on our planet, with a broad spectrum of habitats (Fig. 1), yet we know very little of what lives in its trenches, across its abyssal plains, around seamounts and along its mid-ocean ridges [1]. Where we have begun to explore and document, around the Ocean Margins, what has been established are that the South Pacific hosts biodiversity and evolutionary hotspots to both West and East (Fig. 2) yet vast expanses of the open ocean lack sufficient data to allow characterization, in between these hotspots [1]. From a different perspective, more than 30 years after the discovery of venting, more than 80% of the world's ridge crests remain completely unexplored for hydrothermal activity [2]. Following an international InterRidge workshop held in June 2010, UK, it was recommended that coordinated investigation of the South Atlantic become an immediate priority (Fig. 3), not least because a similar investigation of the South Pacific would requires a much greater burden of shiptime, following established exploration methodologies, and in at least some latitudes require a new technological approach [3]. Bathymetric projection of the South Pacific Ocean (reproduced from German et al., 2011) with numbered field locations: 1, Tonga-Kermadec arc; 2, deep-ocean trenches; (3) mid-plate seamounts of the Louisville Ridge; 4 & 6, Pacific-Antarctic Ridge; 5 & 8, abyssal plains; 7, Southern EPR; 9, Chile margin; 10, Bransfield Strait back-arc basin. HFI* map (<uri>www.coml.org</uri>) showing how biodiversity hot-spots to West and East in the South Pacific are separated by areas devoid of data. *HFI: Hurlbert's First Index is a sample-size independent proxy for species richness. Here, colours (red = high) show predicted numbers of distinct species in a random sample of 50 observations; white: areas still awaiting collection of 50+ observations.