A5087968079- Methane Hydrates and Related Phenomena
- Seismic Waves and Analysis
- Earthquake Detection and Analysis
- Ionosphere and magnetosphere dynamics
- Geophysics and Gravity Measurements
- Solar and Space Plasma Dynamics
- Seismology and Earthquake Studies
- Microbial Community Ecology and Physiology
- Marine and coastal ecosystems
- Isotope Analysis in Ecology
- Heavy metals in environment
- Mass Spectrometry Techniques and Applications
- Geochemistry and Elemental Analysis
- Soil Carbon and Nitrogen Dynamics
- Geology and Paleoclimatology Research
- Metabolomics and Mass Spectrometry Studies
- Analytical chemistry methods development
- Radioactive element chemistry and processing
- Marine Biology and Ecology Research
- Mercury impact and mitigation studies
- Analytical Chemistry and Chromatography
- Genomics and Phylogenetic Studies
- Hydrocarbon exploration and reservoir analysis
- Vibrio bacteria research studies
- Geochemistry and Geologic Mapping
Oregon State University
2018-2025
University of Minnesota
2023-2025
University of Minnesota System
2024-2025
Massachusetts Institute of Technology
2012-2024
Woods Hole Oceanographic Institution
2013-2024
Southern California University for Professional Studies
2024
Scripps Institution of Oceanography
2024
University of Washington
2024
Twin Cities Orthopedics
2024
Florida State University
2024
Significance Iron limits marine production across one third of the surface ocean. The chemical form iron in these regions is unknown, but it well established that molecular speciation affects microbial competition for uptake. Here we show abundance and identity siderophores, strong iron-binding compounds secreted by microbes to enhance uptake, changes iron-replete iron-deficient South Pacific Ocean. In low-iron regions, amphiphilic siderophores are particularly abundant, suggesting a...
The distribution of dissolved iron (Fe), total organic Fe-binding ligands, and siderophores were measured between the surface 400 m at Station ALOHA, a long term ecological study site in North Pacific Subtropical Gyre. Dissolved Fe concentrations low throughout water column strong ligands exceeded all depths; varying from 0.9 nmol L-1 to 1.6 below 150 m. Although does not appear limit microbial production, we nevertheless found nearly depths, indicating some populations microbes responding...
Organic ligands dominate the speciation of iron in ocean. Little is known, however, about chemical composition and distribution these compounds. Here, we describe a method to detect low concentrations organic Fe using reverse-phase high-performance liquid chromatography (HPLC) tandem multicollector inductively coupled plasma mass spectrometry. This technique can be used screen seawater marine cultures for target compounds that isolated structurally characterized. Sensitive detection (<1...
Organic ligands form strong complexes with many trace elements in seawater. Various metals can compete for the same ligand chelation sites, and final speciation of bound is determined by relative binding affinities, concentrations uncomplexed metal concentrations, association/dissociation kinetics. Different have a wide range affinities specificities. However, chemical composition these marine environment remains poorly constrained, which has hindered progress modeling speciation. In this...
New members of the synechobactin siderophore suite with variable hydroxamate chain length were discovered using an LCMS based pipeline for sensitive characterization iron complexes.
Abstract Coastal upwelling of nutrients and metals along eastern boundary currents fuels some the most biologically productive marine ecosystems. Although iron is a main driver productivity in many these regions, cycling acquisition by microbes remain poorly constrained, part due to unknown composition organic ligands that keep bioavailable solution. In this study, we investigated ligand discrete water samples collected across highly California system. Siderophores were observed distinct...
We introduce a cheminformatics approach that combines highly selective and orthogonal structure elucidation parameters; accurate mass, MS/MS (MS²), NMR into single analysis platform to accurately identify unknown metabolites in untargeted studies. The starts with an LC-MS feature, then the experimental information of effectively filter out false positive candidate structures based on their predicted spectra. demonstrate model mixture, we uncatalogued secondary metabolite Arabidopsis...
Abstract. Mercury bioaccumulation in open-ocean food webs depends on the net rate of inorganic mercury conversion to monomethylmercury water column. We measured significant methylation rates across large gradients oxygen utilization oligotrophic central Pacific Ocean. Overall, over 24 h incubation periods were comparable those previously published from Arctic and Mediterranean waters despite differences productivity between these marine environments. In contrast previous studies that have...
We report on the mechanism of a series ZnII-activated magnetic resonance contrast agents that modulate access water to paramagnetic GdIII ion create an increase in relaxivity upon binding ZnII. In absence and presence ZnII, coordination at center is modulated by appended ZnII groups. These groups were systematically varied optimize change binding. observe least one aminoacetate must be present as coordinating group bind effectively inhibit water. At two are required efficiently creating...
Extensive microdiversity within Prochlorococcus , the most abundant marine cyanobacterium, occurs at scales from a single droplet of seawater to ocean basins. To interpret structuring role variations in genetic potential, as well metabolic and physiological acclimation, we developed mechanistic constraint-based modeling framework that incorporates full suite genes, proteins, reactions, pigments, biochemical compositions 69 sequenced isolates spanning pangenome. Optimizing each strain local,...
Marine dissolved organic matter (DOM) contains a complex mixture of small molecules that eludes rapid biological degradation. Spatial and temporal variations in the abundance DOM reflect existence fractions are removed from ocean over different time scales, ranging seconds to millennia. However, it remains unknown whether intrinsic chemical properties these components relate their persistence. Here, we elucidate compare molecular compositions distinct with lability along water column North...
The GEOTRACES program has greatly expanded measurements of dissolved trace metal concentrations across ocean basins, but to understand the behavior and cycling metals their impacts on primary productivity, we must chemical forms in which they are present environment. Organic ligands play a central role speciation marine environment, controlling reactivity bioavailability. Here, an overview contributions made understanding through advancing our knowledge distribution, sources, sinks...
The rate of uranium accumulation in oceanic sediments from seawater is controlled by bottom water oxygen concentrations and organic carbon fluxes—two parameters that are linked to deep ocean storage CO 2 . To investigate glacial‐interglacial changes what known as authigenic U, we have developed a rapid method for its determination simple addition procedure foraminiferal trace element analysis. Foraminiferal calcite acts low U substrate (U/Ca < 15 nmol/mol) upon which accumulates reducing...
Bacteria and phytoplankton form close associations in the ocean that are driven by exchange of chemical compounds. The bacterial signal 2-heptyl-4-quinolone (HHQ) slows growth; however, mechanism responsible remains unknown.
Iron (Fe) availability has well-known effects on plant and microbial metabolism, but its interspecies interactions are poorly understood. The purpose of this study was to investigate metabolite exchange between the grass Brachypodium distachyon strain Bd21 soil bacterium Pseudomonas fluorescens SBW25::gfp/lux (SBW25) during Fe limitation under axenic conditions. We compared transcriptional profiles root exudate metabolites B. plants grown semihydroponically with without SBW25 inoculation...
Wastewater is a significant source of copper to freshwater environments, which can severely harm aquatic life. The bioavailability and toxicity in water are influenced by its complexation with dissolved organic matter (DOM). Speciation models, like the biotic ligand model (BLM) that guides Cu regulations, assume DOM dominated humic substances. Research suggests anthropogenic compounds wastewater discharge may be important binding ligands, although their identities remain largely unknown. To...
Abstract Climate‐driven warming is projected to intensify wildfires, increasing their frequency and severity globally. Wildfires are an increasingly significant source of atmospheric deposition, delivering nutrients, organic matter, trace metals coastal open ocean waters. These inputs have the potential fertilize or inhibit microbial growth, yet ecological impacts remain poorly understood. This study examines how ash leachate, derived from 2017 Thomas Fire in California lab‐produced Oregon...
Current understanding of dissolved iron (Fe) speciation in the ocean is based on two fundamentally different approaches: electrochemical methods that measure bulk properties a heterogeneous ligand pool and liquid chromatography mass spectrometry characterize ligands at molecular level. Here, we describe method for simultaneously determining Fe–ligand dissociation rate constants (kd) suites naturally occurring seawater by monitoring exchange ligand-bound 56Fe with 57Fe using...