Preliminary Observations of the Abyssal Megafauna of Kiribati

Erik Simon-Lledó,Daniel O B Jones,Samuel Thompson,Adrian Flynn,John Parianos,Christina Pomee,Andrew Yool

doi:10.3389/fmars.2019.00605

Abstract

We report on preliminary observations of the abyssal megafauna communities in the exclusive economic zone of Kiribati, a huge abyssal area with few previous studies. These observations also provide useful context for marine minerals exploration within the EEZ and for the neighbouring Clarion Clipperton Zone (CCZ), where deep-sea mining operations are planned. Seafloor images collected during seabed mining exploration were used to characterise megafaunal communities (fauna > 1 cm) in three abyssal plain areas in the eastern Kiribati EEZ (study area extending from 1-5°N and 173-156°W). Additionally, hydrographic features in each of the survey locations were inferred by reference to near-seabed current flows modelled using open-sourced oceanographic data. The images showed a dominance of foraminiferal organisms. Metazoan communities were high in morphospecies richness but had low density. These general patterns were comparable to abyssal megabenthic communities in the CCZ. There was evidence of spatial variation between the assemblages in Kiribati, but there was a relatively large pool of shared morphospecies across the entire study area. Low metazoan density constrained detailed assessment of spatial variation and diversity at local scales. This finding is instructive of the levels of sampling effort required to determine spatial patterns in low density abyssal communities. The results of this study are preliminary observations that will be useful to guide future biological survey design and marine spatial planning strategies.

Highlights

The Republic of Kiribati is a Pacific Micronesian small island state comprised of three island groups: the more populous Gilbert Islands in the West, the largely uninhabited Phoenix Islands in the middle and Line Islands to the East
The Line Islands form the westernmost boundary of the Clarion Clipperton Zone (CCZ, at 2–20◦N; 115–155◦W), which is of significant interest for polymetallic nodules
A total of 15,196 foraminifera specimens and 1948 metazoans, all >1 cm, were recorded across all the study areas surveyed within the Kiribati exclusive economic zone (EEZ)

Summary

Introduction

The Republic of Kiribati is a Pacific Micronesian small island state comprised of three island groups: the more populous Gilbert Islands in the West, the largely uninhabited Phoenix Islands in the middle and Line Islands to the East. The three groups of islands each occur on major Cretaceous volcanic chains (Epp, 1984) that form approximately NW-SE oriented ridge systems rising from the abyssal seafloor in the central Pacific. The total land area of Kiribati is only 811 km (Rotjan et al, 2014), the exclusive economic zone (EEZ) covers around 3.5 million km and >89% of this is abyssal (>4000 m water depth) ocean (Weatherall et al, 2015). Marine mineral exploration in Kiribati has been intermittent since the early 1980s (e.g., Gauss, 1980) and has revealed extensive deposits of polymetallic nodules and metalliferous sediments on the abyssal seafloor and ferromanganese crust resources on the seamount areas (Okamoto, 2005). The Line Islands form the westernmost boundary of the Clarion Clipperton Zone (CCZ, at 2–20◦N; 115–155◦W), which is of significant interest for polymetallic nodules. Baseline knowledge of the environment is important in developing plans for exploitation of mineral resources and management of mining activities in areas of high uncertainty like the deep-sea

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