John Pohlman, PhD
John Pohlman is a Research Chemist with the Woods Hole Coastal and Marine Science Center Gas Hydrates Project.
Science and Products
Filter Total Items: 53
Diversity and biogeochemical structuring of bacterial communities across the Porangahau ridge accretionary prism, New Zealand
Sediments from the Porangahau ridge, located off the northeastern coast of New Zealand, were studied to describe bacterial community structure in conjunction with differing biogeochemical regimes across the ridge. Low diversity was observed in sediments from an eroded basin seaward of the ridge and the community was dominated by uncultured members of the Burkholderiales. Chloroflexi/GNS and Deltap
Authors
L.J. Hamdan, P.M. Gillevet, J. W. Pohlman, M. Sikaroodi, J. Greinert, R.B. Coffin
Methane hydrate-bearing seeps as a source of aged dissolved organic carbon to the oceans
Marine sediments contain about 500-10,000 Gt of methane carbon, primarily in gas hydrate. This reservoir is comparable in size to the amount of organic carbon in land biota, terrestrial soils, the atmosphere and sea water combined, but it releases relatively little methane to the ocean and atmosphere. Sedimentary microbes convert most of the dissolved methane to carbon dioxide. Here we show that a
Authors
J. W. Pohlman, J.E. Bauer, W.F. Waite, C.L. Osburn, N.R. Chapman
Macroscopic biofilms in fracture-dominated sediment that anaerobically oxidize methane
Methane release from seafloor sediments is moderated, in part, by the anaerobic oxidation of methane (AOM) performed by consortia of archaea and bacteria. These consortia occur as isolated cells and aggregates within the sulfate-methane transition (SMT) of diffusion and seep-dominant environments. Here we report on a new SMT setting where the AOM consortium occurs as macroscopic pink to orange bio
Authors
B.R. Briggs, J. W. Pohlman, M. Torres, M. Riedel, E.L. Brodie, F.S. Colwell
Modeling sulfate reduction in methane hydrate-bearing continental margin sediments: Does a sulfate-methane transition require anaerobic oxidation of methane?
The sulfate‐methane transition (SMT), a biogeochemical zone where sulfate and methane are metabolized, is commonly observed at shallow depths (1–30 mbsf) in methane‐bearing marine sediments. Two processes consume sulfate at and above the SMT, anaerobic oxidation of methane (AOM) and organoclastic sulfate reduction (OSR). Differentiating the relative contribution of each process is critical to esti
Authors
A. Malinverno, John W. Pohlman
Chemical and isotopic signature of bulk organic matter and hydrocarbon biomarkers within mid-slope accretionary sediments of the northern Cascadia margin gas hydrate system
The chemical and isotopic compositions of sedimentary organic matter (SOM) from two mid-slope sites of the northern Cascadia margin were investigated during Integrated Ocean Drilling Program (IODP) Expedition 311 to elucidate the organic matter origins and identify potential microbial contributions to SOM. Gas hydrate is present at both locations (IODP Sites U1327 and U1328), with distinct pattern
Authors
Masanori Kaneko, Hiroshi Shingai, John W. Pohlman, Hiroshi Naraoka
Methane sources and production in the northern Cascadia margin gas hydrate system
The oceanographic and tectonic conditions of accretionary margins are well-suited for several potential processes governing methane generation, storage and release. To identify the relevant methane evolution pathways in the northern Cascadia accretionary margin, a four-site transect was drilled during Integrated Ocean Drilling Program Expedition 311. The δ13C values of methane range from a minimum
Authors
John W. Pohlman, Masanori Kaneko, Verena B. Heuer, Richard B. Coffin, Michael Whiticar
Permafrost gas hydrates and climate change: Lake-based seep studies on the Alaskan north slope
The potential interactions between climate change and methane hydrate destabilization are among the most societally-relevant aspects of gas hydrates research. Massive dissociation of deep marine methane hydrates following rapid Earth warming is the most plausible explanation for carbon isotopic data that imply widespread release of microbial methane during the Late Paleocene Thermal Maximum (~55 m
Authors
M.J. Wooller, Carolyn D. Ruppel, John W. Pohlman, M.B. Leigh, M. Heintz, K. Walter Anthony
Methane sources in gas hydrate-bearing cold seeps: Evidence from radiocarbon and stable isotopes
Fossil methane from the large and dynamic marine gas hydrate reservoir has the potential to influence oceanic and atmospheric carbon pools. However, natural radiocarbon (14C) measurements of gas hydrate methane have been extremely limited, and their use as a source and process indicator has not yet been systematically established. In this study, gas hydrate-bound and dissolved methane recovered fr
Authors
J. W. Pohlman, J.E. Bauer, E. A. Canuel, K.S. Grabowski, D.L. Knies, C.S. Mitchell, Michael J. Whiticar, R.B. Coffin
Gas hydrate drilling transect across northern Cascadia margin - IODP Expedition 311
A transect of four sites (U1325, U1326, U1327 and U1329) across the northern Cascadia margin was established during Integrated Ocean Drilling Program Expedition 311 to study the occurrence and formation of gas hydrate in accretionary complexes. In addition to the transect sites, a fifth site (U1328) was established at a cold vent with active fluid flow. The four transect sites represent different
Authors
M. Riedel, Timothy S. Collett, M.J. Malone
The stable carbon isotope biogeochemistry of acetate and other dissolved carbon species in deep subseafloor sediments at the northern Cascadia Margin
Ocean drilling has revealed the existence of vast microbial populations in the deep subseafloor, but to date little is known about their metabolic activities. To better understand the biogeochemical processes in the deep biosphere, we investigate the stable carbon isotope chemistry of acetate and other carbon-bearing metabolites in sediment pore-waters. Acetate is a key metabolite in the cycling o
Authors
Verena B. Heuer, John W. Pohlman, Marta E. Torres, Marcus Elvert, Kai-Uwe Hinrichs
Mid-Pliocene Planktic Foraminifer Census Data and Alkenone Unsaturation Indices from Ocean Drilling Program Hole 677A
The U.S. Geological Survey is conducting a long-term study of mid-Pliocene climatic and oceanographic conditions. One of the key elements of the study involves the use of quantitative composition of planktic foraminifer assemblages in conjunction with other proxies to constrain estimates of sea-surface temperature (SST) and to identify major oceanographic boundaries and water masses.
Raw census
Authors
Marci Robinson, Rocio Caballero, Emily Pohlman, Timothy Herbert, Victoria Peck, Harry Dowsett
Methane hydrate formation in turbidite sediments of northern Cascadia, IODP Expedition 311
Expedition 311 of the Integrated Ocean Drilling Program (IODP) to northern Cascadia recovered gas-hydrate bearing sediments along a SW-NE transect from the first ridge of the accretionary margin to the eastward limit of gas-hydrate stability. In this study we contrast the gas gas-hydrate distribution from two sites drilled ~ 8??km apart in different tectonic settings. At Site U1325, drilled on a d
Authors
M.E. Torres, A.M. Trehu, N. Cespedes, M. Kastner, U.G. Wortmann, J.-H. Kim, P. Long, A. Malinverno, J. W. Pohlman, M. Riedel, T. Collett
Science and Products
Filter Total Items: 53
Diversity and biogeochemical structuring of bacterial communities across the Porangahau ridge accretionary prism, New Zealand
Sediments from the Porangahau ridge, located off the northeastern coast of New Zealand, were studied to describe bacterial community structure in conjunction with differing biogeochemical regimes across the ridge. Low diversity was observed in sediments from an eroded basin seaward of the ridge and the community was dominated by uncultured members of the Burkholderiales. Chloroflexi/GNS and Deltap
Authors
L.J. Hamdan, P.M. Gillevet, J. W. Pohlman, M. Sikaroodi, J. Greinert, R.B. Coffin
Methane hydrate-bearing seeps as a source of aged dissolved organic carbon to the oceans
Marine sediments contain about 500-10,000 Gt of methane carbon, primarily in gas hydrate. This reservoir is comparable in size to the amount of organic carbon in land biota, terrestrial soils, the atmosphere and sea water combined, but it releases relatively little methane to the ocean and atmosphere. Sedimentary microbes convert most of the dissolved methane to carbon dioxide. Here we show that a
Authors
J. W. Pohlman, J.E. Bauer, W.F. Waite, C.L. Osburn, N.R. Chapman
Macroscopic biofilms in fracture-dominated sediment that anaerobically oxidize methane
Methane release from seafloor sediments is moderated, in part, by the anaerobic oxidation of methane (AOM) performed by consortia of archaea and bacteria. These consortia occur as isolated cells and aggregates within the sulfate-methane transition (SMT) of diffusion and seep-dominant environments. Here we report on a new SMT setting where the AOM consortium occurs as macroscopic pink to orange bio
Authors
B.R. Briggs, J. W. Pohlman, M. Torres, M. Riedel, E.L. Brodie, F.S. Colwell
Modeling sulfate reduction in methane hydrate-bearing continental margin sediments: Does a sulfate-methane transition require anaerobic oxidation of methane?
The sulfate‐methane transition (SMT), a biogeochemical zone where sulfate and methane are metabolized, is commonly observed at shallow depths (1–30 mbsf) in methane‐bearing marine sediments. Two processes consume sulfate at and above the SMT, anaerobic oxidation of methane (AOM) and organoclastic sulfate reduction (OSR). Differentiating the relative contribution of each process is critical to esti
Authors
A. Malinverno, John W. Pohlman
Chemical and isotopic signature of bulk organic matter and hydrocarbon biomarkers within mid-slope accretionary sediments of the northern Cascadia margin gas hydrate system
The chemical and isotopic compositions of sedimentary organic matter (SOM) from two mid-slope sites of the northern Cascadia margin were investigated during Integrated Ocean Drilling Program (IODP) Expedition 311 to elucidate the organic matter origins and identify potential microbial contributions to SOM. Gas hydrate is present at both locations (IODP Sites U1327 and U1328), with distinct pattern
Authors
Masanori Kaneko, Hiroshi Shingai, John W. Pohlman, Hiroshi Naraoka
Methane sources and production in the northern Cascadia margin gas hydrate system
The oceanographic and tectonic conditions of accretionary margins are well-suited for several potential processes governing methane generation, storage and release. To identify the relevant methane evolution pathways in the northern Cascadia accretionary margin, a four-site transect was drilled during Integrated Ocean Drilling Program Expedition 311. The δ13C values of methane range from a minimum
Authors
John W. Pohlman, Masanori Kaneko, Verena B. Heuer, Richard B. Coffin, Michael Whiticar
Permafrost gas hydrates and climate change: Lake-based seep studies on the Alaskan north slope
The potential interactions between climate change and methane hydrate destabilization are among the most societally-relevant aspects of gas hydrates research. Massive dissociation of deep marine methane hydrates following rapid Earth warming is the most plausible explanation for carbon isotopic data that imply widespread release of microbial methane during the Late Paleocene Thermal Maximum (~55 m
Authors
M.J. Wooller, Carolyn D. Ruppel, John W. Pohlman, M.B. Leigh, M. Heintz, K. Walter Anthony
Methane sources in gas hydrate-bearing cold seeps: Evidence from radiocarbon and stable isotopes
Fossil methane from the large and dynamic marine gas hydrate reservoir has the potential to influence oceanic and atmospheric carbon pools. However, natural radiocarbon (14C) measurements of gas hydrate methane have been extremely limited, and their use as a source and process indicator has not yet been systematically established. In this study, gas hydrate-bound and dissolved methane recovered fr
Authors
J. W. Pohlman, J.E. Bauer, E. A. Canuel, K.S. Grabowski, D.L. Knies, C.S. Mitchell, Michael J. Whiticar, R.B. Coffin
Gas hydrate drilling transect across northern Cascadia margin - IODP Expedition 311
A transect of four sites (U1325, U1326, U1327 and U1329) across the northern Cascadia margin was established during Integrated Ocean Drilling Program Expedition 311 to study the occurrence and formation of gas hydrate in accretionary complexes. In addition to the transect sites, a fifth site (U1328) was established at a cold vent with active fluid flow. The four transect sites represent different
Authors
M. Riedel, Timothy S. Collett, M.J. Malone
The stable carbon isotope biogeochemistry of acetate and other dissolved carbon species in deep subseafloor sediments at the northern Cascadia Margin
Ocean drilling has revealed the existence of vast microbial populations in the deep subseafloor, but to date little is known about their metabolic activities. To better understand the biogeochemical processes in the deep biosphere, we investigate the stable carbon isotope chemistry of acetate and other carbon-bearing metabolites in sediment pore-waters. Acetate is a key metabolite in the cycling o
Authors
Verena B. Heuer, John W. Pohlman, Marta E. Torres, Marcus Elvert, Kai-Uwe Hinrichs
Mid-Pliocene Planktic Foraminifer Census Data and Alkenone Unsaturation Indices from Ocean Drilling Program Hole 677A
The U.S. Geological Survey is conducting a long-term study of mid-Pliocene climatic and oceanographic conditions. One of the key elements of the study involves the use of quantitative composition of planktic foraminifer assemblages in conjunction with other proxies to constrain estimates of sea-surface temperature (SST) and to identify major oceanographic boundaries and water masses.
Raw census
Authors
Marci Robinson, Rocio Caballero, Emily Pohlman, Timothy Herbert, Victoria Peck, Harry Dowsett
Methane hydrate formation in turbidite sediments of northern Cascadia, IODP Expedition 311
Expedition 311 of the Integrated Ocean Drilling Program (IODP) to northern Cascadia recovered gas-hydrate bearing sediments along a SW-NE transect from the first ridge of the accretionary margin to the eastward limit of gas-hydrate stability. In this study we contrast the gas gas-hydrate distribution from two sites drilled ~ 8??km apart in different tectonic settings. At Site U1325, drilled on a d
Authors
M.E. Torres, A.M. Trehu, N. Cespedes, M. Kastner, U.G. Wortmann, J.-H. Kim, P. Long, A. Malinverno, J. W. Pohlman, M. Riedel, T. Collett