I am scientist Emeritus with the Environmental Hydrodynamics Branch of the Earth Systems Process Division of the USGS Water Resources Mission Area.
Our mission is to understand the processes that affect availability, movement, and quality of the Nation’s water resources. I’m currently engaged in studies of the fate of chromium in contaminated groundwater, the ecology and geochemistry of Mono Lake, CA, and the role of bacteria in transforming hydrocarbons in the subsurface.
Professional Studies/Experience
- May 1984 to Present: Research Oceanographer, National Research Program, U.S. Geological Survey, Menlo Park, CA
- Sept. 1981 to May 1984: Oceanographer III, University of Washington, Seattle, WA
- Jan. 1977 to Sept. 1981: Research and Teaching Assistant, University of Southern California, Los Angeles, CA
- April 1973 to Dec. 1976: Research Technician, Lamont Doherty Earth Observatory, Columbia University, Palisades, NY
Education and Certifications
Education
1972 B.A., Marine Science, Southampton College, Long Island University
1980 M.S., Geological Science, University of Southern California
Science and Products
A Two-Year Water-Column Time Series of Geochemical Data During a Limnological Shift in Mono Lake, California, 2017-2018
Mono Lake is a hypersaline (approximately 85 ppt), alkaline (pH 9.8), closed-basin lake located in the eastern Sierra Nevada Mountains of California, USA (38 degrees N, 119 degrees W). Water enters the lake primarily from snowmelt and exits by evaporation (approximately 1 m/yr). This hydrological condition, plus weathering reactions in the lake's tributaries, produce the uniquely high salinity and
Aqueous and Solid Phase Chemistry of Sequestration and Re-oxidation of Chromium in Experimental Microcosms with Sand and Sediment from Hinkley, CA
Cr(VI) contaminated groundwater at Hinkley is undergoing bioremediation using added ethanol as a reductant in a volume of the aquifer defined as the In-situ Reduction Zone (IRZ). This treatment effectively reduces Cr(VI) to Cr(III) which is rapidly sequestered by sorption to aquifer particle surfaces and by co-precipitation within iron or manganese bearing minerals forming in place as reduction pr
Growth of cultured Picocystis strain ML in the presence of arsenic, and occurrence of arsenolipids in these Picocystis as well as biota and sediment from Mono Lake, California
Mono Lake is a hypersaline soda lake rich in dissolved inorganic arsenic with its primary production currently dominated by Picocystis str. ML. We set out to determine if this picoplankter could metabolize inorganic arsenic, and in doing so form unusual arsenolipids (e.g., methylated arsinoyl ribosides) as reported in other saline ecosystems and by halophilic algae. We cultivated Picocystis str. M
Filter Total Items: 52
Arsenolipids in cultured Picocystis strain ML, and their occurrence in biota and sediment from Mono Lake, California
Primary production in Mono Lake, a hypersaline soda lake rich in dissolved inorganic arsenic, is dominated by Picocystis strain ML. We set out to determine if this photoautotrophic picoplankter could metabolize inorganic arsenic and in doing so form unusual arsenolipids (e.g., arsenic bound to 2-O-methyl ribosides) as reported in other saline ecosystems and by halophilic algae. We cultivated Picoc
Metabolic capability and phylogenetic diversity of Mono Lake during a bloom of the eukaryotic phototroph Picocystis sp. strain ML
Algal blooms in lakes are often associated with anthropogenic eutrophication; however, they can occur without the human introduction of nutrients to a lake. A rare bloom of the alga Picocystis sp. strain ML occurred in the spring of 2016 at Mono Lake, a hyperalkaline lake in California, which was also at the apex of a multiyear-long drought. These conditions presented a unique sampling opportunity
Acetylenotrophy: A hidden but ubiquitous microbial metabolism?
Acetylene (IUPAC name: ethyne) is a colorless, gaseous hydrocarbon, composed of two triple bonded carbon atoms attached to hydrogens (C2H2). When microbiologists and biogeochemists think of acetylene, they immediately think of its use as an inhibitory compound of certain microbial processes and a tracer for nitrogen fixation. However, what is less widely known is that anaerobic and aerobic microor
Methane fluxes from tropical coastal lagoons surrounded bymangroves, Yucatán, Mexico
Methane concentrations in the water column and emissions to the atmosphere were determined for three tropical coastal lagoons surrounded by mangrove forests on the Yucatán Peninsula, Mexico. Surface water dissolved methane was sampled at different seasons over a period of 2 years in areas representing a wide range of salinities and anthropogenic impacts. The highest surface water methane concentra
Genome sequence of the photoarsenotrophic bacterium Ectothiorhodospira sp. strain BSL-9, isolated from a hypersaline alkaline arsenic-rich extreme environment
The full genome sequence of Ectothiorhodospira sp. strain BSL-9 is reported here. This purple sulfur bacterium encodes an arxA-type arsenite oxidase within the arxB2AB1CD gene island and is capable of carrying out “photoarsenotrophy” anoxygenic photosynthetic arsenite oxidation. Its genome is composed of 3.5 Mb and has approximately 63% G+C content.
The genetic basis of anoxygenic photosynthetic arsenite oxidation
“Photoarsenotrophy”, the use of arsenite as an electron donor for anoxygenic photosynthesis, is thought to be an ancient form of phototrophy along with the photosynthetic oxidation of Fe(II), H2S, H2, and NO2-. Photoarsenotrophy was recently identified from Paoha Island's (Mono Lake, CA) arsenic-rich hot springs. The genomes of several photoarsenotrophs revealed a gene cluster, arxB2AB1CD, where a
Methane and sulfate dynamics in sediments from mangrove-dominated tropical coastal lagoons, Yucatan, Mexico
Porewater profiles in sediment cores from mangrove-dominated coastal lagoons (Celestún and Chelem) on the Yucatán Peninsula, Mexico, reveal the widespread coexistence of dissolved methane and sulfate. This observation is interesting since dissolved methane in porewaters is typically oxidized anaerobically by sulfate. To explain the observations we used a numerical transport-reaction model that was
Metabolism of reduced methylated sulfur compounds in anaerobic sediments and by a pure culture of an estuarine methanogen
Addition of dimethylsulfide (DMS), dimethyldisulfide (DMDS), or methane thiol (MSH) to a diversity of anoxic aquatic sediments (e.g., fresh water, estuarine, alkaline/hypersaline) stimulated methane production. The yield of methane recovered from DMS was often 52 to 63%, although high concentrations of DMS (as well as MSH and DMDS) inhibited methanogenesis in some types of sediments. Production o
Stable carbon isotope fractionation during bacterial acetylene fermentation: Potential for life detection in hydrocarbon-rich volatiles of icy planet(oid)s
We report the first study of stable carbon isotope fractionation during microbial fermentation of acetylene (C2H2) in sediments, sediment enrichments, and bacterial cultures. Kinetic isotope effects (KIEs) averaged 3.7 ± 0.5‰ for slurries prepared with sediment collected at an intertidal mudflat in San Francisco Bay and 2.7 ± 0.2‰ for a pure culture of Pelobacter sp. isolated from these sediments.
Microbiological oxidation of antimony(III) with oxygen or nitrate by bacteria isolated from contaminated mine sediments
Bacterial oxidation of arsenite [As(III)] is a well-studied and important biogeochemical pathway that directly influences the mobility and toxicity of arsenic in the environment. In contrast, little is known about microbiological oxidation of the chemically similar anion antimonite [Sb(III)]. In this study, two bacterial strains, designated IDSBO-1 and IDSBO-4, which grow on tartrate compounds and
A microbial arsenic cycle in sediments of an acidic mine impoundment: Herman Pit, Clear Lake, California
The involvement of prokaryotes in the redox reactions of arsenic occurring between its +5 [arsenate; As(V)] and +3 [arsenite; As(III)] oxidation states has been well established. Most research to date has focused upon circum-neutral pH environments (e.g., freshwater or estuarine sediments) or arsenic-rich “extreme” environments like hot springs and soda lakes. In contrast, relatively little work h
Methane oxidation and molecular characterization of methanotrophs from a former mercury mine impoundment
The Herman Pit, once a mercury mine, is an impoundment located in an active geothermal area. Its acidic waters are permeated by hundreds of gas seeps. One seep was sampled and found to be composed of mostly CO2 with some CH4 present. The δ13CH4 value suggested a complex origin for the methane: i.e., a thermogenic component plus a biological methanogenic portion. The relatively 12C-enriched CO2 sug
Science and Products
- Data
A Two-Year Water-Column Time Series of Geochemical Data During a Limnological Shift in Mono Lake, California, 2017-2018
Mono Lake is a hypersaline (approximately 85 ppt), alkaline (pH 9.8), closed-basin lake located in the eastern Sierra Nevada Mountains of California, USA (38 degrees N, 119 degrees W). Water enters the lake primarily from snowmelt and exits by evaporation (approximately 1 m/yr). This hydrological condition, plus weathering reactions in the lake's tributaries, produce the uniquely high salinity andAqueous and Solid Phase Chemistry of Sequestration and Re-oxidation of Chromium in Experimental Microcosms with Sand and Sediment from Hinkley, CA
Cr(VI) contaminated groundwater at Hinkley is undergoing bioremediation using added ethanol as a reductant in a volume of the aquifer defined as the In-situ Reduction Zone (IRZ). This treatment effectively reduces Cr(VI) to Cr(III) which is rapidly sequestered by sorption to aquifer particle surfaces and by co-precipitation within iron or manganese bearing minerals forming in place as reduction prGrowth of cultured Picocystis strain ML in the presence of arsenic, and occurrence of arsenolipids in these Picocystis as well as biota and sediment from Mono Lake, California
Mono Lake is a hypersaline soda lake rich in dissolved inorganic arsenic with its primary production currently dominated by Picocystis str. ML. We set out to determine if this picoplankter could metabolize inorganic arsenic, and in doing so form unusual arsenolipids (e.g., methylated arsinoyl ribosides) as reported in other saline ecosystems and by halophilic algae. We cultivated Picocystis str. M - Publications
Filter Total Items: 52
Arsenolipids in cultured Picocystis strain ML, and their occurrence in biota and sediment from Mono Lake, California
Primary production in Mono Lake, a hypersaline soda lake rich in dissolved inorganic arsenic, is dominated by Picocystis strain ML. We set out to determine if this photoautotrophic picoplankter could metabolize inorganic arsenic and in doing so form unusual arsenolipids (e.g., arsenic bound to 2-O-methyl ribosides) as reported in other saline ecosystems and by halophilic algae. We cultivated PicocMetabolic capability and phylogenetic diversity of Mono Lake during a bloom of the eukaryotic phototroph Picocystis sp. strain ML
Algal blooms in lakes are often associated with anthropogenic eutrophication; however, they can occur without the human introduction of nutrients to a lake. A rare bloom of the alga Picocystis sp. strain ML occurred in the spring of 2016 at Mono Lake, a hyperalkaline lake in California, which was also at the apex of a multiyear-long drought. These conditions presented a unique sampling opportunityAcetylenotrophy: A hidden but ubiquitous microbial metabolism?
Acetylene (IUPAC name: ethyne) is a colorless, gaseous hydrocarbon, composed of two triple bonded carbon atoms attached to hydrogens (C2H2). When microbiologists and biogeochemists think of acetylene, they immediately think of its use as an inhibitory compound of certain microbial processes and a tracer for nitrogen fixation. However, what is less widely known is that anaerobic and aerobic microorMethane fluxes from tropical coastal lagoons surrounded bymangroves, Yucatán, Mexico
Methane concentrations in the water column and emissions to the atmosphere were determined for three tropical coastal lagoons surrounded by mangrove forests on the Yucatán Peninsula, Mexico. Surface water dissolved methane was sampled at different seasons over a period of 2 years in areas representing a wide range of salinities and anthropogenic impacts. The highest surface water methane concentraGenome sequence of the photoarsenotrophic bacterium Ectothiorhodospira sp. strain BSL-9, isolated from a hypersaline alkaline arsenic-rich extreme environment
The full genome sequence of Ectothiorhodospira sp. strain BSL-9 is reported here. This purple sulfur bacterium encodes an arxA-type arsenite oxidase within the arxB2AB1CD gene island and is capable of carrying out “photoarsenotrophy” anoxygenic photosynthetic arsenite oxidation. Its genome is composed of 3.5 Mb and has approximately 63% G+C content.The genetic basis of anoxygenic photosynthetic arsenite oxidation
“Photoarsenotrophy”, the use of arsenite as an electron donor for anoxygenic photosynthesis, is thought to be an ancient form of phototrophy along with the photosynthetic oxidation of Fe(II), H2S, H2, and NO2-. Photoarsenotrophy was recently identified from Paoha Island's (Mono Lake, CA) arsenic-rich hot springs. The genomes of several photoarsenotrophs revealed a gene cluster, arxB2AB1CD, where aMethane and sulfate dynamics in sediments from mangrove-dominated tropical coastal lagoons, Yucatan, Mexico
Porewater profiles in sediment cores from mangrove-dominated coastal lagoons (Celestún and Chelem) on the Yucatán Peninsula, Mexico, reveal the widespread coexistence of dissolved methane and sulfate. This observation is interesting since dissolved methane in porewaters is typically oxidized anaerobically by sulfate. To explain the observations we used a numerical transport-reaction model that wasMetabolism of reduced methylated sulfur compounds in anaerobic sediments and by a pure culture of an estuarine methanogen
Addition of dimethylsulfide (DMS), dimethyldisulfide (DMDS), or methane thiol (MSH) to a diversity of anoxic aquatic sediments (e.g., fresh water, estuarine, alkaline/hypersaline) stimulated methane production. The yield of methane recovered from DMS was often 52 to 63%, although high concentrations of DMS (as well as MSH and DMDS) inhibited methanogenesis in some types of sediments. Production oStable carbon isotope fractionation during bacterial acetylene fermentation: Potential for life detection in hydrocarbon-rich volatiles of icy planet(oid)s
We report the first study of stable carbon isotope fractionation during microbial fermentation of acetylene (C2H2) in sediments, sediment enrichments, and bacterial cultures. Kinetic isotope effects (KIEs) averaged 3.7 ± 0.5‰ for slurries prepared with sediment collected at an intertidal mudflat in San Francisco Bay and 2.7 ± 0.2‰ for a pure culture of Pelobacter sp. isolated from these sediments.Microbiological oxidation of antimony(III) with oxygen or nitrate by bacteria isolated from contaminated mine sediments
Bacterial oxidation of arsenite [As(III)] is a well-studied and important biogeochemical pathway that directly influences the mobility and toxicity of arsenic in the environment. In contrast, little is known about microbiological oxidation of the chemically similar anion antimonite [Sb(III)]. In this study, two bacterial strains, designated IDSBO-1 and IDSBO-4, which grow on tartrate compounds andA microbial arsenic cycle in sediments of an acidic mine impoundment: Herman Pit, Clear Lake, California
The involvement of prokaryotes in the redox reactions of arsenic occurring between its +5 [arsenate; As(V)] and +3 [arsenite; As(III)] oxidation states has been well established. Most research to date has focused upon circum-neutral pH environments (e.g., freshwater or estuarine sediments) or arsenic-rich “extreme” environments like hot springs and soda lakes. In contrast, relatively little work hMethane oxidation and molecular characterization of methanotrophs from a former mercury mine impoundment
The Herman Pit, once a mercury mine, is an impoundment located in an active geothermal area. Its acidic waters are permeated by hundreds of gas seeps. One seep was sampled and found to be composed of mostly CO2 with some CH4 present. The δ13CH4 value suggested a complex origin for the methane: i.e., a thermogenic component plus a biological methanogenic portion. The relatively 12C-enriched CO2 sug