Cedric Magen research interests

From the Arctic Ocean to the beaches of Florida

Cédric Magen, Ph.D

Postdoctoral fellow

Curriculum Vitae

Contact infos:
Department of Oceanography
117 N. Woodward Ave
Oceanography/Statistics Building
32306, Tallahassee, FL
USA
Tel: +1 850 644-6985
Fax: +1 850 644-2581
email: magen@ocean.fsu.edu

I did my PhD at McGill University, Montreal. There, I was lucky to participate in the Canadian Arctic Shelf Exchange Study (CASES) that mobilized the ice-breaker Amundsen for one full year in the Beaufort Sea, Canadian Arctic. I spent a total of 18 weeks on this research vessel that became my home for part of the tough Arctic winter, including Christmas and New Year's eve. The boat spent the winter in Franklin Bay, waiting for the ice to become thin enough to get out and explore the waters that just opened in late Spring. Before becoming prisoners of the ice, we cruised the Mackenzie Shelf and Amundsen Gulf waters, in order to sample as much as possible of this vast unknown area. I was interested mostly in the sediment geochemistry, and I also looked at the origin and fate of the organic matter from the water column to the sediment itself. Box-Coring in winter in the Arctic becomes rapidly a challenge, not because of rough seas, more because of extremely cold conditions. For the anecdote, there was one time when the box-core that we had just retrieved arrived totally frozen in our laboratory.

Our work on board consisted on slicing the cores and extract the porewaters by squeezing the sediment. Using solid state Au/Hg microelectrodes, we analyzed the first 5-10 cm of the sediment for dissolved O₂, Mn(II), Fe(II), and sulfides. Back at McGill University, we analyzed the total length of the core (~ 40 cm) for reactive Mn and Fe oxides, as well as organic and inorganic carbon and stable isotopes of the organic matter (d¹³C and d¹⁵N).

Publications related to my work in the Arctic:

C. Magen, A. Mucci and B. Sundby. (in prep) Rates of Mn and Fe oxide reduction in Arctic sediments: results of amendment experiments.

C. Magen, G. Chaillou, C. Gilbert, S. A. Crowe, A. Mucci and B. Sundby. (in prep) Iron and manganese define the organic carbon sedimentation regimes in the Beaufort Sea.

C. Magen, G. Chaillou, S. A. Crowe, A. Mucci, B. Sundby, A. Gao, R. Makabe and H. Sasaki. (in press) Origin and fate of particulate organic matter in the Southern Beaufort Sea - Amundsen Gulf region, Canadian Arctic. Estuar. Coast. Shelf S. (article in pdf)

A. Mucci, A. Forest, L. Fortier, M. Fukuchi, J. Grant, H. Hattori, P. Hill, G. Lintern, R. Makabe, C. Magen, L. Miller, M. Sampei, H. Sasaki, B. Sundby, T. Walker and P. Wassmann. 2008. Organic and Inorganic Fluxes. In Fortier, L., Barber, D., Michaud, J. (Editors), On thin ice: A synthesis of the Canadian Arctic Shelf Exchange Study (CASES). Aboriginal Issue Press, University of Manitoba, Winnipeg, Manitoba, pp. 117-145.

Other publications:

S.A. Crowe, C.A. Jones, S. Katsev, C. Magen, A.H. O'Neill, A. Sturm, D.E. Canfield, G.D. Haffner, A. Mucci, B. Sundby and D.A. Fowle. 2008.

Photoferrotrophs thrive in an Archean Ocean analogue. PNAS 105(41), 15938-15943. (article in pdf)

R. Sempere, E. Dafner, F. Van Wambeke, D. Lefevre, C. Magen, S. Allegre, F. Bruyant, M. Bianchi and L. Prieur. 2003. Distribution and cycling of total organic carbon across the Almeria-Oran Front in the Mediterranean Sea: Implications for carbon cycling in the western basin. J. Geophys. Res. Oceans 108(C11), 3361, doi:10.1029/2002JC001475.

After 5 years spent in cold Montreal, I migrated to Florida to work in Markus Huettel's group at Florida State University. Working in Florida made me change my working habits. I traded a nice and warm ice breaker for the beaches of Florida where I have to keep the sun and the bugs away at all time.

Not only did I change climate, but I also took a slightly different path as I am now looking at sandy shelf sediments. The main difference is that these sands are permeable and allow advection of water. Due to wave action or tidal currents, sea water circulates constantly through these sands, which can be seen as a gigantic filter. The organic matter that is present in sea water is therefore continuously exposed to the numerous bacteria inhabiting the sands, that thus act as a degradation bioreactor.

I am involved in a project where I look at the degradation of dissolved organic carbon (DOC) when seawater is being filtered through sand beds. In the field, we deploy benthic chambers that we dig into the sediment. Each chamber is equipped with a stirring disc that induces a flow of water through the underlying sands. Using labile DOC marked with stable isotopes (DO¹³C), we look for the production of DI¹³C to asses the degradation of labile DOC. We also look into the changes of molecular composition of the organic matter after filtration.

In the laboratory, I use columns filled with sand and through which a solution of labile DO¹³C is passed. With this experimental setup, I can look at the different parameters that control the degradation of DO¹³C, such as flow velocity, temperature, light and oxygen.