The central theme of my research is to
understand the processes that control the distribution of trace elements in the water column of the ocean. The approaches
are multi-faceted, and extend to explorations of elemental behavior in large lakes, in controlled cultures of phytoplankton,
and in the past ocean. We are particularly interested in the role of trace elements in single celled primary producers, and
in turn how the physiological processes in these organisms influence the global scale concentrations and distribution of the
elements. Our lab specializes in careful analyses of very low concentrations of trace elements in natural waters, particles,
cells, and biominerals. We are leaders in the applications of plasma-source mass spectrometry to problems in marine geochemistry.
My research in the last few years has been focused on several distinct, but interacting, questions:
- How do climate-related variables in ocean chemistry, such as iron availability and CO2 content, affect the uptake
of bioactive trace metals such as Mn, Zn, Cu, Cd, and Co by phytoplankton and bacteria?
- What are the connections between the biochemical roles of trace metals in phytoplankton and the vertical flux of metals
associated with the “biological pump” in the open and coastal ocean?
- Does metal uptake by primary producers in the Southern Ocean differ fundamentally from that of temperate latitude organisms?
- Can large oligotrophic lakes such as Lake Superior experience Fe limitation of primary production?
- How does the biogeochemical cycling of phosphorus operate when the total dissolved phosphorus concentration is extremely low?
- What can we learn about the trace element composition of seawater in the past by analysis of these elements in the skeletal
aragonite of corals?
- What are the best methods for standardizing and codifying the efficient collection and accurate elemental analysis of marine
particulate matter?
We have pursued these questions using a combination of lab based research and field work to Lake Superior, the
North Atlantic, the California margin upwelling system, the Bering Sea, and the Southern Ocean.
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