Marine phytoplankton are responsible for about half of the global primary production and for a major fraction of reverse weathering on the Earth. Some of the carbon dioxide they fix is exported to the deep sea; some of the SiO2 precipitated by diatoms and CaCO3 precipitated by coccolithophores is accumulated in sediments and eventually subjected to diagenesis. What physical and chemical factors control the growth and activity of phytoplankton is the overarching question addressed in my research group. Our focus is on trace metals, some of which are essential for phytoplankton growth (e.g., Fe), some are toxic (e.g., Hg), some are both (e.g., Cd).
Graduate Students
I am currently interested in nutrient and metal uptake mechanisms in phytoplankton. Utilizing nickelās slow uptake kinetics, I am trying to find examples of co-limitation due to possible physiological restraints such as cell surface area. The hope is that this will make possible future work on the ecological niche of diatoms and other marine phytoplankton and their relationship to oceanic trace metal cycling.
I am interested in the biogeochemical cycle of trace elements in the oceans. Currently I am exploring Cd carbonic anhydrase, the first known Cd specific enzyme in marine diatoms. From this project I am hoping to find conservative genetic information about Cd usage by marine organisms and connect it to the evolution of marine biogeochemistry.
Research interest: I am interested in the biogeochemical cycling of trace metals in the ocean, especially the understanding of the environmental and biological factors that influence their uptake by phytoplankton, transfer through food chain and removal from surface water.
Research interest: I am interested in exploring the interactions between inorganic carbon acquisition and trace metals as micronutrients (e.g., Fe, Cd, and Zn) in marine phytoplankton under elevated CO2 conditions, and hope that this would provide an insight into influence of increasing atmospheric CO2 on ocean productivity and therefore global carbon cycle.
Post Doctoral Research Scientists
Thomas Wichard
My research focuses on the bioavailability of trace metals and the nitrogen cycle in soils. I am interested in the chemical form and bioavailability of trace metals like molybdenum and vanadium, because these elements are found at the active center of the nitrogenase that fixes dinitrogen. Specifically, I look at the production of bis- and tris-catecholates, which are produced by the soil bacterium Azotobacter in order to make the metal available to the organism. I will utilize e.g. X-ray spectroscopy to study trace metal speciation in environmental samples. My goal is to understand how trace metal availability and the regulation of nitrogenase-activity influence nitrogen fixation.
My research interests are centred on clarifying, with molecular, physiological and biochemical approaches, the operation of the 'CO2-concentrating mechanism' or CCM in marine diatoms. Diatoms are responsible for fixing between 30 and 50 billion metric tonnes of CO2 in the upper oceans every year (roughly 40% of the global total) but our understanding of how they do this is far from complete. Consequently, they play a critical role in regulating atmospheric CO2 levels which, in turn, has implications in regulating our climate. A key interest of mine is in establishing the relative importance of key environmental parameters such as pCO2, trace metal (Zn, Co, Fe) bioavailability and light intensity in the regulation of the diatom CCM. In an era of unprecedented increases in atmospheric CO2 levels, our ability to predict the response of phytoplankton communities to such environmental perturbation will rest on a firm understanding on how CO2 acquisition is regulated in the first place.
Mercury Methylation
Jean-Philippe Bellenger
Role of molybdenum in soils
Gone But Not Forgotten
I am generally interested in the strategies employed by phytoplankton to compete for limiting nutrients in the marine environment, as well as the biochemical plasticity of the demand for nutrients for growth under limiting conditions. Specifically, I have been recently working on the mechanism of Fe acquisition from organic Fe compounds by marine diatoms, and hope to use this mechanistic understanding to evaluate the interactions among Fe, diatoms and other phototrophs in marine ecosystems.
My research focuses on investigating the physiological and biochemical role that iron storage proteins play in marine cyanobacteria. Iām currently working on the overexpression of putative bacterioferritin genes in Trichodesmium.
I am interested in understanding the mechanisms of trace metal contaminant transformation in the environment. My research focuses on investigating the physiology and biochemistry of mercury methylation in sulfate-reducing bacteria, to better understand what controls the natural production of this bioaccumulating neurotoxin.
Novel environmental analytical techniques to study biogeochemical cycling of trace elements. Trace metal-algae interaction in maintaining metal homeostasis. Reduced sulfur species in control metal speciation and bioavailability. I'm currently working on the release of dissolved gluthione from diatom in response to Cu stress, and will start to study the possible role of Cu bioavailability in Fe uptake of algae.
Biogeochemical cycling, redox dynamics and chemical speciation of trace metals in aquatic ecosystems. Trace metal nutrition and toxicity to phytoplankton. Phytoplankton's extra-cellular enzyme activity - geochemical and environmental significance. Organic nutrients utilization by E. hux, role of exo-enzymes. http://www.iui-eilat.ac.il/indexE.htm
My research interests are in the interaction between marine phytoplankton and their major and micro nutrients at enzymatic level, with the goal of understanding the mechanisms in controlling the biogeochemical cycling of the elements. My current studies are focusing on P acquisition by Emiliania huxleyi. Preliminary evidences show that coccoliths may enhance alkaline phosphatase activity in E.hux. I am also working to prove whether the alkaline phosphatase in E.hux.can utilize Cd to acquire inorganic phosphate in the ocean.
Research interests: Biogeochemical cycle of mercury; identification of the source of methylmercury to the oceans and marine organisms; atmospheric sources, transport, and chemistry of mercury; wet and dry deposition of heavy metals and trace elements.
My research focuses on stable isotopes and algal physiology and the questions I address are motivated by geological and global change issues. Primarily, I look at the interactions between trace metals and macronutrient metabolism in phytoplankton and their impacts on global nutrient cycling. My goal is to relate biochemical and molecular work on enzymes to current and past oceanographic conditions through the use of stable isotopes.
I am interested in the interactions between metal chemical species and marine microorganisms and the implications for carbon cycling. My research utilizes molecular and genomic approaches as well as analytical and physiological methods to understand the cyanobacterium and diatoms and their relationship to the biogeochemical cycles of Co, Cd, Zn and Fe.
Princeton University
Department of Geosciences