Insights into the abundance and diversity of abyssal megafauna in a polymetallic-nodule region in the eastern Clarion-Clipperton Zone.

Diva J Amon,Aurélie Goineau,Helena Wiklund,Craig R Smith,Amanda F Ziegler,Thomas G Dahlgren,Adrian G Glover,Andrew J Gooday

doi:10.1038/srep30492

Abstract

There is growing interest in mining polymetallic nodules in the abyssal Clarion-Clipperton Zone (CCZ) in the Pacific. Nonetheless, benthic communities in this region remain poorly known. The ABYSSLINE Project is conducting benthic biological baseline surveys for the UK Seabed Resources Ltd. exploration contract area (UK-1) in the CCZ. Using a Remotely Operated Vehicle, we surveyed megafauna at four sites within a 900 km2 stratum in the UK-1 contract area, and at a site ~250 km east of the UK-1 area, allowing us to make the first estimates of abundance and diversity. We distinguished 170 morphotypes within the UK-1 contract area but species-richness estimators suggest this could be as high as 229. Megafaunal abundance averaged 1.48 ind. m−2. Seven of 12 collected metazoan species were new to science, and four belonged to new genera. Approximately half of the morphotypes occurred only on polymetallic nodules. There were weak, but statistically significant, positive correlations between megafaunal and nodule abundance. Eastern-CCZ megafaunal diversity is high relative to two abyssal datasets from other regions, however comparisons with CCZ and DISCOL datasets are problematic given the lack of standardised methods and taxonomy. We postulate that CCZ megafaunal diversity is driven in part by habitat heterogeneity.

Highlights

Microbes, (2) establishing how community structure, biodiversity and benthic carbon cycling vary across the UK-1 contract area and with environmental parameters such as nodule cover, and (3) assessing faunal population connectivity within the UK-1 contract area and across the CCZ
We present the first baseline data for megafauna in the UK-1 exploration contract area based on Remotely Operated Vehicle (ROV) surveys and samples collected during the first cruise of the ABYSSLINE Project in 2013
We provide the first insights into megafaunal abundance and diversity from the UK-1 exploration contract area and the eastern CCZ

Summary

Results

A total of 180 megafaunal morphotypes (metazoan and protistan) was identified in ROV video surveys during the AB01 cruise (both UK-1 Stratum A and the EPIRB sites) (Figs 2,3 and Supplementary Table S2) (Amon et al, in prep.) This is likely an underestimate due to poor image resolution, difficulty identifying fauna from images, and the presence of cryptic species. Forty-eight morphotypes were only observed within the UK-1 contract area, whereas ten were noted only at the EPIRB site (see Supplementary Table S2) This difference in morphotype richness is likely due to a higher sampling effort in UK-1 rather than from distinct species ranges. The five most abundant morphotypes across all quantitative transects were the ophiuroid, Ophiomusium cf glabrum, three plate-like xenophyophore morphotypes, and the primnoid Abyssoprimnoa gemina (Table 2 and Fig. 2). There were no marked differences between the proportions of obligate soft-sediment dwellers (2.5% vs. 3.1%), facultative (66.3% vs. 59.1%) and obligate hard-substrate dwellers (31.3% vs. 37.8%) in areas of low versus medium nodule cover

Discussion

Study Site and Methods

Author Contributions

Additional Information