Skidaway Institute of Oceanography
10 Ocean Science Circle
Savannah, Ga. 31411
Office: (912) 598-2414
Fax: (912) 598-2310
B.S. Biology and Chemistry, Williams College, 2004
PhD. Chemical Oceanography, MIT/Woods Hole Joint Program, 2013
Research in the Ohnemus Lab focuses on marine particles: the dynamic mixture of living and non-living, mostly microscopic, power-houses of the ocean. Particles consume, transport, and transform the elements of the ocean, and their interactions determine how/where/why the ocean uses and recycles major nutrients and micronutrient “trace elements”.
Marine particles are a complicated mixture of things, generally collected by carefully and cleanly filtering seawater: living organisms like phytoplankton (algae) and bacteria, non-living dust from the continents and ocean sediments, and other phases like iron and manganese oxides or human-produced plastics. Particles can be large (and rapidly sinking) or small (and more passively transported).
At sea, our lab collects particles using both large-volume, size-fractionated filtration (McLane pumps) and smaller-scale bottle filtrations. We also use optical instrumentation to observe particles in the ocean. Back on land, we measure the bulk composition of particles using multi-element mass spectrometry (digestion of filtered particles using chemical techniques). We also use synchrotron light (x-rays produced at National Laboratories) to examine the composition of individual marine particles as small as single organisms. With collaborators, we then incorporate these measurements into regional-scale and global-scale biogeochemical/ecosystem models.
Key questions our group is interested in:
-What organisms and phases are key trace elements (Al, Cd, Co, Cu, Fe, Mn, Ni, P, Pb, Th, Ti, V, Zn—among others!) associated with at different oceanographic sites? How can we better discern these associations using various analytical and statistical techniques?