Hydrochemical properties and chemocline of the Sansha Yongle Blue Hole in the South China Sea

Xie, Lian; Wang, Baodong; Pu, Xinming; Xin, Ming; He, Pinjing; Li, Chengxuan; Zhang, Xuelei; Li, Tiegang

doi:10.1016/j.scitotenv.2018.08.333

Cited by 35 publications

(70 citation statements)

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“…The greatest Nitrospina abundance was at 90 m in the blue hole (7.2%), at 300 m at C3 (8.6%), and at 300 m at C4 (4.2%), suggesting that this genus occupied a wide range of niches. were detected 20 . The microbial composition in this water layer was distinct, with the most abundant 16S rRNA amplicon sequences affiliated with the γ-Proteobacteria (11.9-42.2%), δ-Proteobacteria (12.0-18.7%), Candidatus OP3 (6.3-13.1%), Planctomycetes (2.0-9.3%), and Candidatus Parcubacteria (3.0-7.8%) ( Fig.…”

Section: Resultsmentioning

confidence: 98%

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Microbial Diversity and Metabolic Potential in the Stratified Sansha Yongle Blue Hole in the South China Sea

Xie

Zhang

et al. 2020

Sci Rep

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The Sansha Yongle Blue Hole is the world's deepest (301 m) underwater cave and has a sharp redox gradient, with oligotrophic, anoxic, and sulfidic bottom seawater. In order to discover the microbial communities and their special biogeochemical pathways in the blue hole, we analyzed the 16S ribosomal RNA amplicons and metagenomes of microbials from seawater depths with prominent physical, chemical, and biological features. Redundancy analysis showed that dissolved oxygen was the most important factor affecting the microbial assemblages of the blue hole and surrounding open sea waters, and significantly explained 44.7% of the total variation, followed by silicate, temperature, sulfide, ammonium, methane, nitrous oxide, nitrate, dissolved organic carbon, salinity, particulate organic carbon, and chlorophyll a. We identified a bloom of Alteromonas (34.9%) at the primary nitrite maximum occurring in close proximity to the chlorophyll a peak in the blue hole. Genomic potential for nitrate reduction of Alteromonas might contribute to this maximum under oxygen decrease. Genes that would allow for aerobic ammonium oxidation, complete denitrification, and sulfuroxidization were enriched at nitrate/nitrite-sulfide transition zone (90 and 100 m) of the blue hole, but not anammox pathways. Moreover, γ-Proteobacterial clade SUP05, ε-Proteobacterial genera Sulfurimonas and Arcobacter, and Chlorobi harbored genes for sulfur-driven denitrification process that mediated nitrogen loss and sulfide removal. In the anoxic bottom seawater (100-300 m), high levels of sulfate reducers and dissimilatory sulfite reductase gene (dsrA) potentially created a sulfidic zone of ~200 m thickness. Our findings suggest that in the oligotrophic Sansha Yongle Blue Hole, o 2 deficiency promotes nitrogen-and sulfur-cycling processes mediated by metabolically versatile microbials. O 2-deficient regions occur throughout global oceans 1. Intermediate layers of the ocean develop O 2-deficient water masses, referred to as oxygen minimum zones (OMZs), due to limitation in photosynthetic O 2 production and high-level aerobic respiration during the degradation of surface-derived organics 2. In these OMZs, such as the Eastern Tropical South Pacific (ETSP) and the Arabian Sea, O 2 concentrations fall below sensor-specific detection limits 3-5. In contrast, the Peru Upwelling Region, the Namibian Shelf, and the Indian Continental Shelf experience episodic plumes of hydrogen sulfide (H 2 S) 6-8. These sulfidic environments are also found in enclosed or semi-enclosed basins, including the Black Sea Basin 9-12 , the Baltic Sea Basin 13-15 , the Cariaco Basin 16,17 , and submarine caves, such as the Bahamian blue holes 18 , the Belize Blue Hole 19 , and the Sansha Yongle Blue Hole 20. In O 2-deficient regions, microbial reactions control key steps in carbon, nitrogen, and sulfur transformation under successional redox gradients extending throughout the water column 21. NO 3 − is the most energetically

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Section: Resultsmentioning

confidence: 98%

“…1) 42 . The physiochemical characteristics are presented in detail in our parallel hydrochemical study 20 . Briefly, the blue hole has a sharp chemocline and sulfidic bottom waters.…”

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confidence: 99%

Microbial Diversity and Metabolic Potential in the Stratified Sansha Yongle Blue Hole in the South China Sea

Xie

Zhang

et al. 2020

Sci Rep

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“…In contrast, the YBH appears to be more isolated from land‐derived sources of organic carbon (OC; Figure ), and there appear to be minimal effects of tidal pumping in the deeper waters of this system (Figure S1). In addition, the permanent thermocline results in stratification of the YBH, which restricts vertical water exchange (Xie et al, ). Thus, we believe that the dominant factor controlling the decrease in DOC concentration from 80‐ to ~140‐m depth of the YBH was extensive degradation, which is coupled to a rapid decline in DO and steady accumulation of H 2 S (Figure ).…”

Section: Discussionmentioning

confidence: 99%

“…The coral reef around the top of the YBH could produce considerable debris flow, which has been observed by divers and the ROV. The analyses of turbidity and suspended particulate matter have also shown high concentrations of particles in the YBH, especially in the chemocline, compared with adjacent sea areas (Bi et al, ; Xie et al, ). These sinking particles are mainly composed by coral detritus, which could provide additional sources of CaCO 3 besides the antecedent carbonate platform in which the YBH formed, and could also provide a continuous POC supply, although the level of primary production (chlorophyll a ) in the surface water was not high (Figure S2f).…”

Section: Discussionmentioning

confidence: 99%

“…These linkages are indicative of a strong redox gradient (as evidenced by changes in Eh) with sulfate reduction as a dominant respiration pathway of OC in many anoxic environments (Thamdrup & Canfield, 1996). Additional studies have also found coupled nitrificationdenitrification along this redox gradient (Xie et al, 2019). In fact, the degradation of OC is clearly not the sole reason for the depletion of DO in the YBH.…”

Section: Controls On the Concentration And Isotopic Compositions Of Docmentioning

confidence: 93%

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Carbon Cycling in the World's Deepest Blue Hole

et al. 2020

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Blue holes are unique geomorphological features with steep biogeochemical gradients and distinctive microbial communities. Carbon cycling in blue holes, however, remains poorly understood. Here we describe potential mechanisms of dissolved carbon cycling in the world's deepest blue hole, the Yongle Blue Hole (YBH), which was recently discovered in the South China Sea. In the YBH, we found some of the lowest concentrations (e.g., 22 μM) and oldest ages (e.g., 6,810 years before present) of dissolved organic carbon, as well as the highest concentrations (e.g., 3,090 μM) and the oldest ages (e.g., 8,270 years before present) of dissolved inorganic carbon observed in oceanic waters. Sharp gradients of dissolved oxygen, H2S, and CH4 and changes in bacterially mediated sulfur cycling with depth indicated that sulfur‐ and/or methane‐based metabolisms are closely linked to carbon cycling in the YBH. Our results showed that the YBH is a unique and easily accessible natural laboratory for examining carbon cycling in anoxic systems, which has potential for understanding carbon dynamics in both paleo and modern oceans—particularly in the context of global change.

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Chemical Links Between Redox Conditions and Estimated Community Proteomes from 16S rRNA and Reference Protein Sequences

Dick

Tan

2022

Microb Ecol

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Environmental influences on community structure are often assessed through multivariate analyses in order to relate microbial abundances to separately measured physicochemical variables. However, genes and proteins are themselves chemical entities; in combination with genome databases, differences in microbial abundances directly encode for chemical variability. We predicted that the carbon oxidation state of inferred community proteomes, obtained by combining taxonomic abundances from published 16S rRNA gene sequencing datasets with predicted microbial proteomes from the NCBI Reference Sequence (RefSeq) database, would reflect environmental oxidation-reduction conditions in various natural and engineered settings including shale gas wells. Our analysis confirms the geobiochemical predictions for environmental redox gradients within and between hydrothermal systems and stratified lakes and marine environments. Where they are present, a common set of taxonomic groups (Gamma-and Deltaproteobacteria and Clostridia) act as drivers of the community-level differences in oxidation state, whereas Flavobacteria most often oppose the overall changes. The geobiochemical signal is largest for the steep redox gradients associated with hydrothermal systems and between surface water and produced fluids from shale gas wells, demonstrating the ability to determine the magnitude of redox effects on microbial communities from 16S sequencing alone.

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Hydrochemical properties and chemocline of the Sansha Yongle Blue Hole in the South China Sea

Cited by 35 publications

References 49 publications

Microbial Diversity and Metabolic Potential in the Stratified Sansha Yongle Blue Hole in the South China Sea

Microbial Diversity and Metabolic Potential in the Stratified Sansha Yongle Blue Hole in the South China Sea

Carbon Cycling in the World's Deepest Blue Hole

Chemical Links Between Redox Conditions and Estimated Community Proteomes from 16S rRNA and Reference Protein Sequences

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