A5025139197- Geology and Paleoclimatology Research
- Marine and coastal ecosystems
- Geochemistry and Elemental Analysis
- Paleontology and Stratigraphy of Fossils
- Marine Biology and Ecology Research
- Microbial Community Ecology and Physiology
- Geological formations and processes
- Coral and Marine Ecosystems Studies
- Geological and Geophysical Studies
- Isotope Analysis in Ecology
- Mercury impact and mitigation studies
- Oceanographic and Atmospheric Processes
- Geochemistry and Geologic Mapping
- Pacific and Southeast Asian Studies
- Planetary Science and Exploration
- Astro and Planetary Science
- Pleistocene-Era Hominins and Archaeology
- Marine and fisheries research
- Hydrocarbon exploration and reservoir analysis
- Radioactive contamination and transfer
- Heavy metals in environment
- Archaeology and ancient environmental studies
- Geological and Geochemical Analysis
- Groundwater and Isotope Geochemistry
- Geomagnetism and Paleomagnetism Studies
Arizona State University
2020-2025
University of Illinois Chicago
2024
GEOMAR Helmholtz Centre for Ocean Research Kiel
2017-2022
Woods Hole Oceanographic Institution
2007-2021
University of Southern California
2014-2015
Massachusetts Institute of Technology
2013
Carl von Ossietzky Universität Oldenburg
2012
Cornell University
2004
We discuss the concept of colimitation primary productivity in aquatic environments, with an emphasis on reconciling this recent advances marine bioinorganic chemistry. Colimitations are divided into three categories basis their mathematical formulations and visualizations: type I, independent nutrient (e.g., N P); II, biochemical substitution Co Zn); III, biochemically dependent Zn C), where ability to acquire one is upon sufficient supply another. The potential for occurring environment...
Protein markers of cyanobacterial stress Nutrients including iron, nitrogen, and phosphorus limit primary productivity in the oceans. Determining how abundant cyanobacteria such as Prochlorococcus adapt to nutrient across marine settings requires accurate molecular assays. Saito et al. developed a proteomic metaproteomic approach capable targeting specific metabolic biomarkers from mixed communities seawater (see Perspective by Moore). proteins are indicative major limiting wide transect...
We present full‐depth zonal sections of total dissolved cobalt, iron, manganese, and labile cobalt from the South Atlantic Ocean. A basin‐scale plume African coast appeared to be a major source metals this region, with high concentrations in oxygen minimum zone Angola Dome extending 2500 km into subtropical gyre. Metal were elevated along coastal shelf, likely due reductive dissolution resuspension particulate matter. Linear relationships between N 2 O, O , as well low surface aluminum...
Abstract There is a converging body of evidence supporting measurable slowdown the Atlantic Meridional Overturning Circulation (AMOC) as climate warms and Northern Hemisphere ice sheets inexorably shrink. Within this context, we assess variability AMOC during Holocene based on marine sediment core retrieved from deep northwest Atlantic, which sensitively recorded large‐scale deglacial transitions in water circulation. While there diffuse notion Labrador Nordic Seas overturning, report...
Abstract. Extensive observations were made during the late Southwest Monsoon of 2004 over Indian and Omani shelves, along a transect that extended from southern coast Oman to central west India, tracking leg US JGOFS expedition (1994–1995) in west. The data are used, conjunction with satellite-derived data, investigate long-term trends chlorophyll sea surface temperature, indicators upwelling intensity, understand factors control primary production (PP) Arabian Sea, focussing on role iron....
We present evidence demonstrating the capability of Phaeocystis antarctica colonies to substitute cobalt (Co) and zinc (Zn) as micronutrients, in which Co limitation is alleviated by additions Zn vice versa. Maximal growth rates biomass were determined fluorescence values obtained under replete no added conditions significantly higher than conditions, suggesting a preference for over Co. The observation Zn‐Co substitution this high‐latitude member Prymnesiophyceae class, coupled with similar...
Abstract. We report the distribution of cobalt (Co) in Ross Sea polynya during austral summer 2005–2006 and following spring 2006. The vertical total dissolved Co (dCo) was similar to soluble reactive phosphate (PO43−), with dCo PO43− showing a significant correlation throughout water column (r2 = 0.87, 164 samples). A strong seasonal signal for observed, most samples having concentrations ranging from ~45–85 pM, whereas values were depleted below these levels by biological activity. Surface...
Abstract Thaumarchaea are among the most abundant microbial groups in ocean, but controls on their abundance and distribution metabolic potential of different subpopulations poorly constrained. Here, two ecotypes ammonia‐oxidizing thaumarchaea were quantified using ammonia monooxygenase ( amoA ) genes across equatorial Pacific Ocean. The shallow, or water column “A” (WCA), ecotype was at depths maximum nitrification rates, its correlated with other biogeochemical indicators remineralization...
Ammonia-oxidizing microorganisms are an important source of the greenhouse gas nitrous oxide (N2O) in aquatic environments. Identifying impact pH on N2O production by ammonia oxidizers is key to understanding how fluxes will respond naturally occurring changes, as well acidification driven anthropogenic CO2. We assessed rates and formation mechanisms communities ammonia-oxidizing bacteria (AOB) archaea (AOA) a lake marine environment, using incubation-based nitrogen (N) stable isotope tracer...
The middle Paleozoic (∼420-350 Myr) records a major increase in ocean-atmosphere oxygen levels; however, the timing and pattern of oxygenation are poorly constrained. Two well-dated North American locations Nevada Illinois were used to generate high-resolution U-isotopic profile (δ238U) spanning ∼70 Myr Paleozoic. Stratigraphic geochemical data support interpretation that represents near-primary record global-ocean redox variations. First-order δ238U trends indicate strongly reducing oceans...
Significance Photosynthetic phytoplankton are the foundation of marine ecosystems. Their growth in sunlit ocean depends on ample supply over a dozen essential elements. Of these elemental nutrients, metal cobalt is found at lowest concentrations seawater, but it unknown whether scarcity impacts growth. We have measured minimum requirements photosynthetic bacterium Prochlorococcus , which flourishes nutrient-poor regions where many other cannot survive. can grow with less than 50 atoms per...
Abstract We studied lunar regolith breccia meteorite Northwest Africa (NWA) 13967 to explore its mineral and clast inventory with special focus on the ubiquitous occurrence of tissintite‐II, a newly recognized, vacancy‐rich high‐pressure clinopyroxene feldspathic, Fe‐ Mg‐enriched composition. Lithic clasts in NWA indicate provenance Feldspathic Highlands Terrane Moon. Most abundant are cumulate impact melt (“poikilitic granulitic breccias”), granular rocks, vitric including spherules,...
Abstract The Arabian Sea is a productive basin where seasonal upwelling and convective mixing result in high surface nutrient concentrations widespread algal blooms. factors controlling primary productivity the are of interest because region contains an intense oxygen minimum zone (OMZ) that major sink for nitrate ocean. A survey iron (Fe) distribution redox chemistry was carried out 2007 to assess its role biogeochemistry, including investigation biological response Fe additions. Results...
Vertical profiles of total dissolved iron (DFe), Fe(II), and hydrographic parameters were obtained along three transects across the continental shelf off Peru in October 2005. Fe(II) DFe concentrations determined using luminol chemiluminescence isotope dilution inductively coupled plasma mass spectrometry (ICP‐MS), respectively. The objective was to study relationships among redox chemistry, nitrogen‐cycle processes, bottom topography, distribution chemistry region. results are most thorough...
Glutathione is an abundant intracellular thiol that involved in the detoxification of reactive oxygen species generated presence light. We used short‐term continuous cultures Emiliania huxleyi and Thalassiosira pseudonana to show a diurnal light cycle causes glutathione undergo at least twofold variations, with maximum concentrations occurring during periods. Cysteine also appear vary E. similar extent, highest night. A complementary field study conducted Salt Pond Falmouth, Massachusetts,...
Abstract. Bioactive trace metals are critical micronutrients for marine microorganisms due to their role in mediating biological redox reactions, and complex biogeochemical processes control distributions. Hydrothermal vents may represent an important source of microorganisms, especially those inhabiting low-iron waters, such as the southwest Pacific Ocean. Previous measurements primordial 3He indicate a significant hydrothermal originating northeastern (NE) Lau Basin, with plume advecting...
Abstract Knowing the Fe3+/ΣFe ratio in minerals is important to understand formation and evolution of their host rocks. Variable in, e.g., garnet accompanied by a change characteristic FeLα FeLβ X-ray emission lines, which can be quantified with electron microprobe measurements using flank method. Previously, required data reduction process determine was complex. Here, we present new tool taking as an example. This Flank Reduction app freely available, graphical user interface (GUI)-driven,...
In addition to characteristic fatty acid methyl esters (FAMEs), biodiesel produced from Isochrysis sp. contains a significant amount (14%, w/w) of predominantly C37 and C38 long-chain alkenones. These compounds are members class lipids known collectively as polyunsaturated alkenones (PULCAs) that by range other prymnesiophyte taxa. The physical properties alkenones, such high melting points (∼60 °C), renders the direct product unsuitable for use diesel fuel but, nonetheless, represents an...