Methane Seeps and Independent Methane Plumes in the South China Sea Offshore Taiwan

Mau, Susan; Tu, Tzu-Hsuan; Becker, Marius; Ferreira, Christian dos Santos; Chen, Jhen‐Nien; Lin, Li‐Hung; Wang, Pei Ling; Lin, Saulwood; Bohrmann, Gerhard

doi:10.3389/fmars.2020.00543

Cited by 18 publications

(12 citation statements)

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“…Assuming that the k CH4 measured at station PM5 during the 19 February cruise is also applicable to the 16 October sampling at this station when the near‐bottom [CH 4 ] was determined to be 695.3 nmol L −1 and the extrapolated seafloor [CH 4 ] reached 5,785 nmol L −1 (Section 4.5), the consumption rate will increase to 21.6 and 179.3 nmol L −1 d −1 , respectively. These rates are at the upper bounds of the aerobic methane oxidation rates reported for marine waters worldwide, including those affected by submarine gas seeps and anthropogenic oil spills (Mau et al., 2020 and references therein). These high methane consumption rates are also consistent with the presence of greenish bacterial mats, presumably composed of methanotrophs, on the seafloor surrounding gas‐venting pockmarks in the LSLE (Bolduc et al., 2008; Lavoie et al., 2010) and with the discovery of methane‐derived authigenic carbonate cements in sediments at certain pockmark sites in this region (Lavoie et al., 2010; Savard et al., 2021).…”

Section: Resultsmentioning

confidence: 84%

Dissolved Methane in the World's Largest Semi‐Enclosed Estuarine System: The Estuary and Gulf of St. Lawrence (Canada)

Xie

Scarratt

et al. 2022

JGR Oceans

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Section: Resultsmentioning

confidence: 84%

Dissolved Methane in the World's Largest Semi‐Enclosed Estuarine System: The Estuary and Gulf of St. Lawrence (Canada)

Xie

Scarratt

et al. 2022

JGR Oceans

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“…Similar sequences have been detected from shallow seawater (1.5 and 7 m deep) at subzero temperatures in the Arctic Ocean ( 105 ) and from shallow sediment (21 m deep) off Santa Barbara, CA ( 106 ), where the seawater temperature is governed by the cold California current. Notable detection is also reported in the water column at a depth of 32 m in the South China Sea, where the water temperature is approximately 27°C, which is above the upper limit for the growth (26°C) of M. sedimenti WF1 T ( 17 , 107 ). Despite these reports, the limited number of detections in shallow waters indicates that low temperature is likely a key factor for most Methyloprofundus species.…”

Section: Discussionmentioning

confidence: 88%

Multispecies Populations of Methanotrophic Methyloprofundus and Cultivation of a Likely Dominant Species from the Iheya North Deep-Sea Hydrothermal Field

Hirayama

Takaki

Abe

et al. 2022

Appl Environ Microbiol

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The Methyloprofundus clade is represented by uncultivated methanotrophic bacterial endosymbionts of deep-sea bathymodiolin mussels, but only a single free-living species has been cultivated to date. This study reveals the existence of free-living Methyloprofundus variants in the Iheya North deep-sea hydrothermal field in the mid-Okinawa Trough. A clade-targeted amplicon analysis of the particulate methane monooxygenase gene ( pmoA ) detected 647 amplicon sequence variants (ASVs) of the Methyloprofundus clade in microbial communities newly formed in in situ colonization systems. Such systems were deployed at colonies of bathymodiolin mussels and a galatheoid crab. These ASVs were classified into 161 species-like groups. The proportion of the species-like groups representing endosymbionts of mussels was unexpectedly low. A methanotrophic bacterium designated as INp10, a likely dominant species in the Methyloprofundus population in this field, was enriched in biofilm formed in a methane-fed cultivation system operated at 10°C. Genomic characterization with the gene transcription dataset of INp10 from biofilm suggested traits advantageous to niche competition in environments, such as mobility, chemotaxis, biofilm formation, offensive and defensive systems, and hypoxia tolerance. The notable metabolic traits INp10 shares with some Methyloprofundus members are the use of lanthanide-dependent XoxF as the sole methanol dehydrogenase due to the absence of the canonical MxaFI, the glycolytic pathway using fructose-6-phosphate aldolase instead of fructose-1,6-bisphosphate aldolase, and the potential to perform partial denitrification from nitrate under oxygen-limited conditions. These findings help better understand ecological strategies of this possibly widespread marine-specific methanotrophic clade. Importance The Iheya North deep-sea hydrothermal field in the mid-Okinawa Trough is characterized by abundant methane derived from organic-rich sediments and diverse chemosynthetic animal species, including those harboring methanotrophic bacterial symbionts such as bathymodiolin mussels Bathymodiolus japonicus and “ Bathymodiolus ” platifrons and a galatheoid crab Shinkaia crosnieri . Symbiotic methanotrophs have attracted significant attention, yet free-living methanotrophs in this environment have not been studied in detail. We focused on the free-living Methyloprofundus spp. that thrive in this hydrothermal field and identified an unexpectedly large number of species-like groups in this clade. Moreover, we enriched and characterized a methanotroph whose genome sequence indicated it corresponds to a new species in the genus Methyloprofundus . This species might be a dominant member of the indigenous Methyloprofundus population. New information on free-living Methyloprofundus spp. suggests that the hydrothermal field is a promising locale to investigate the adaptive capacity and associated genetic diversity of Methyloprofundus .

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“…To date, no pure cultures of bacteria of the Hyd24‐01 clade exist; however, this clade has been reported from other methane‐rich sites, including surface sediments of Haakon Mosby Mud Volcano (Lösekann et al, 2007). The uncultured clade IheB2‐23 was first detected in the water column of the northern South China Sea (Mau et al, 2020).…”

Section: Discussionmentioning

confidence: 99%

A carbonate corrosion experiment at a marine methane seep: The role of aerobic methanotrophic bacteria

et al. 2023

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Methane seeps are typified by the formation of authigenic carbonates, many of which exhibit corrosion surfaces and secondary porosity believed to be caused by microbial carbonate dissolution. Aerobic methane oxidation and sulfur oxidation are two processes capable of inducing carbonate corrosion at methane seeps. Although the potential of aerobic methanotrophy to dissolve carbonate was confirmed in laboratory experiments, this process has not been studied in the environment to date. Here, we report on a carbonate corrosion experiment carried out in the REGAB Pockmark, Gabon‐Congo‐Angola passive margin, in which marble cubes were deployed for 2.5 years at two sites (CAB‐B and CAB‐C) with apparent active methane seepage and one site (CAB‐D) without methane seepage. Marble cubes exposed to active seepage (experiment CAB‐C) were found to be affected by a new type of microbioerosion. Based on 16S rRNA gene analysis, the biofilms adhering to the bioeroded marble mostly consisted of aerobic methanotrophic bacteria, predominantly belonging to the uncultured Hyd24‐01 clade. The presence of abundant 13C‐depleted lipid biomarkers including fatty acids (n‐C16:1ω8c, n‐C18:1ω8c, n‐C16:1ω5t), various 4‐mono‐ and 4,4‐dimethyl sterols, and diplopterol agrees with the dominance of aerobic methanotrophs in the CAB‐C biofilms. Among the lipids of aerobic methanotrophs, the uncommon 4α‐methylcholest‐8(14)‐en‐3β,25‐diol is interpreted to be a specific biomarker for the Hyd24‐01 clade. The combination of textural, genetic, and organic geochemical evidence suggests that aerobic methanotrophs are the main drivers of carbonate dissolution observed in the CAB‐C experiment at the REGAB pockmark.

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Methane Seeps and Independent Methane Plumes in the South China Sea Offshore Taiwan

Cited by 18 publications

References 94 publications

Dissolved Methane in the World's Largest Semi‐Enclosed Estuarine System: The Estuary and Gulf of St. Lawrence (Canada)

Dissolved Methane in the World's Largest Semi‐Enclosed Estuarine System: The Estuary and Gulf of St. Lawrence (Canada)

Multispecies Populations of Methanotrophic Methyloprofundus and Cultivation of a Likely Dominant Species from the Iheya North Deep-Sea Hydrothermal Field

A carbonate corrosion experiment at a marine methane seep: The role of aerobic methanotrophic bacteria

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