From the Surface to the Deep-Sea: Bacterial Distributions across Polymetallic Nodule Fields in the Clarion-Clipperton Zone of the Pacific Ocean

Abstract

Marine bacteria regulate fluxes of matter and energy essential for pelagic and benthic organisms and may also be involved in the formation and maintenance of commercially valuable abyssal polymetallic nodules. Future mining of these nodule fields is predicted to have substantial effects on biodiversity and physicochemical conditions in mined areas. Yet, the identity and distributions of bacterial populations in deep-sea sediments and associated polymetallic nodules has received relatively little attention. We examined bacterial communities using high-throughput sequencing of bacterial 16S rRNA gene fragments from samples collected in the water column, sediment, and polymetallic nodules in the Pacific Ocean (bottom depth ≥4,000 m) in the eastern Clarion-Clipperton Zone. Operational taxonomic units (OTUs; defined at 99% 16S rRNA gene identity) affiliated with JTB255 (Gammaproteobacteria) and Rhodospirillaceae (Alphaproteobacteria) had higher relative abundances in the nodule and sediment habitats compared to the water column. Rhodobiaceae family and Vibrio OTUs had higher relative abundance in nodule samples, but were less abundant in sediment and water column samples. Bacterial communities in sediments and associated with nodules were generally similar; however, 5,861 and 6,827 OTUs found in the water column were retrieved from sediment and nodule habitats, respectively. Cyanobacterial OTUs clustering among Prochlorococcus and Synechococcus were detected in both sediments and nodules, with greater representation among nodule samples. Such results suggest that vertical export of typically abundant photic-zone microbes may be an important process in delivery of water column microorganisms to abyssal habitats, potentially influencing the structure and function of communities in polymetallic nodule fields.

Habitat filtering of bacterioplankton communities above polymetallic nodule fields and sediments in the Clarion‐Clipperton zone of the Pacific Ocean

“…The taxonomic composition varied across the different realms of the water column, where, for example, Cyanobacteria had higher average relative abundance in the epipelagic compared with lower depths and Gammaproteobacteria had higher average relative abundance at lower depths compared with the epipelagic (Supporting Information Fig. S2; see also Lindh et al ., ). In the epipelagic and mesopelagic regions variation in environmental factors independent of spatial factors exerted significant control on total bacterioplankton composition (Table ; Fig.…”

“…Raw sequence data generated from Illumina Miseq were processed as described in Lindh et al . () using the UPARSE pipeline (Edgar, ). Sequence reads were merged and quality filtered and subsequently clustered into OTUs at 99% 16S rRNA gene sequence similarity.…”

“…In the present article we used taxonomic information on bacterioplankton assemblages from the entire water column in the eastern CCZ of the Pacific Ocean determined from 16S rRNA amplicon data obtained from Lindh et al (2017) to include new theoretical ecology analyses for the present study. In that study, seawater samples were collected during the AB02 research cruise in the CCZ.…”

“…In that study, seawater samples were collected during the AB02 research cruise in the CCZ. Planktonic biomass was harvested from seawater samples as described in Lindh et al (2017). In brief, seawater was sampled from eight discrete depths within the water column (5,125,300,500,1000,2000 and 3000 m) and at 5 m altitude above the seafloor (bottom depths ranging from 4025 to 4218 m) using 10 L Niskin sampling bottles affixed to a conductivity, temperature, depth (CTD) rosette.…”

“…Hence, nutrients, attachment surfaces and potential energy sources introduced in the sediment plume could be available for, and/or influence, the pelagic food web (Oebius et al, 2001). It is therefore important to predict how mining activities might change community composition of particular bacterioplankton taxa responding to the sediment plume (see also Lindh et al, 2017;Shulse et al, 2017).…”