Barbeau, K. A. University of California,
Moffett, J. A. Woods Hole Oceanographic Institution,

Planktonic protozoan grazers have the potential to significantly affect the biogeochemical cycling of particle-associated trace metals in marine systems. This is due both to the importance of protists as consumers of bacterial-sized particles, and to the unique low-pH, enzyme-rich microenvironment of the grazer food vacuole. To investigate the mechanistics of grazer-mediated trace metal cycling, we have conducted a series of laboratory experiments in two-organism model systems consisting of bacteria and protozoan grazers. C-14 and a variety of trace metal isotopes (Fe-59, Th-234, Cr-51) were used to follow the chemical transformation of bacterial carbon and associated trace metals by several different protozoan grazer species. Results indicate that protozoan grazers are equally able to mobilize intracellular and extracellular trace metals. In some cases, protozoan regeneration of trace metals appears to lead to the formation of metal-organic complexes. Protozoan grazing may also generate colloidal material that can scavenge trace metals and, via aggregation, lead to an increase in the metal/organic carbon ratio of aggregated particles. Factors likely to influence these processes include the degree of concentration of the system, specifics of protozoan digestive chemistry, and the surface chemistry of the bacterial prey.
Day: Friday, Feb. 5
Time: 02:00 - 02:15pm
Location: Sweeney Center
Code: SS28FR0200S