Abstract:

With a warming ocean whose physical stratification and biological productivity are changing, the depth range and areal extent of oxygen minimum zones (OMZ) in the world’s oceans are increasing. This has tremendous effects on benthic and pelagic fisheries, but it also can affect the cycling of essential trace metals like iron or toxic ones like copper or arsenic. The problem is that simply measuring their concentrations or chemical forms in the water column tells you nothing about what processes are controlling them. For example, soluble Fe⁺² (FeII) can be produced from the reduction of iron oxide particles in the water column, but it can also be transported from anoxic coastal sediments – it may not be produced in the OMZ. How do we separate what chemistry is happening in situ (in the water column) from physical transport? We have combined the coupled measurements of trace metal speciation (chemical forms) in the dissolved and particulate states, ²²⁸Ra, ²³⁴Th, and simple diagnostic modeling techniques to separate ocean chemistry from physics. For this seminar, I will illustrate how we used this approach to examine the cycling of nitrogen (NO₂^-/NO₃^-), iodine (I^-/IO₃^-), iron (FeII/FeIII), arsenic (AsIII/AsV), and selenium (SeIV+VI/Se0)in the large OMZ off Peru during the 2013 US GEOTRACES GP16 expedition.

 Dr. Cutter is a biogeochemist interested in the fundamental processes linking the biology and chemistry of aquatic systems. He also races sailboats and does adventure motorcycling.

 For detailed information about Prof. Cutter, please check https://www.odu.edu/directory/people/g/gcutter

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