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.
Highlights
Polymetallic nodules containing high levels of manganese, iron, cobalt, and nickel can form extensive fields on abyssal plains, raising the prospect of future deep-sea mining on a commercial scale (Ghosh and Mukhopadhyay, 2000; Wegorzewski and Kuhn, 2014)
We examined the structure of bacterial communities in watercolumn, sediment and polymetallic-nodule habitats at water depths ≥4,000 m in the eastern Clarion-Clipperton Zone (CCZ; Pacific Ocean) through amplification and sequencing of bacterial
For each sediment layer and for nodule samples, there were significant differences in the Shannon index between the four study areas (Two-way ANOVA, p < 0.001, df = 16, n = 331), with the Area of Particular Environmental Interest (APEI)-6 location having lower diversity overall compared to Ocean Mineral Singapore (OMS) Stratum A, UK-1 Stratum A and UK-1 Stratum B (Tukey’s posthoc test, p < 0.01, df = 3)
Summary
Polymetallic nodules containing high levels of manganese, iron, cobalt, and nickel can form extensive fields on abyssal plains, raising the prospect of future deep-sea mining on a commercial scale (Ghosh and Mukhopadhyay, 2000; Wegorzewski and Kuhn, 2014). In the abyssal Pacific Ocean, work focused on microbial diversity identified specific bacterial operational taxonomic units (OTUs) associated with nodules, including those clustering among Alpha- and Gammaproteobacteria (Tully and Heidelberg, 2013; Wu et al, 2013; Blöthe et al, 2015; Shulse et al, 2016). It has been suggested that particular bacterial populations have notable mechanisms of energy cycling (Tully and Heidelberg, 2016), and are involved in the precipitation of metals potentially drive the formation and maintenance of nodules (Burnett and Nealson, 1981; Myers and Nealson, 1988; Ehrlich, 2001; Wang et al, 2008; Wu et al, 2013; Blöthe et al, 2015). To date, there is still relatively little known about the identity and distributions of bacteria dwelling in deep-sea sediments and associated with polymetallic nodules
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
