HR: 14:25h
AN: V53B-04    [Abstracts]
TI: Zinc isotope variations in natural and cultured marine phytoplankton.
AU: * John, S G
EM: sjohn@mit.edu
AF: MIT, MIT E34-272 42-44 CARLETON ST., CAMBRIDGE, MA 02139
AU: Bergquist, B A
EM: bardot@mit.edu
AF: MIT, MIT E34-272 42-44 CARLETON ST., CAMBRIDGE, MA 02139
AU: Boyle, E A
EM: eaboyle@mit.edu
AF: MIT, MIT E34-272 42-44 CARLETON ST., CAMBRIDGE, MA 02139
AB: Zn is an essential micronutrient for marine phytoplankton. Zn distribution in the ocean is largely controlled by biological uptake, being drawn down from several nanomolar concentrations in the deep ocean to picomolar concentrations in the surface ocean. Zn isotopes may record this biological activity based on the preferential uptake of lighter Zn isotopes by phytoplankton. Marechal et. al. (2000) attribute a seasonal cycle in the Zn isotope composition of sediment trap material and global variations in the Zn isotope composition of manganese nodules to this biological fractionation. To better understand the processes controlling the distribution of Zn isotopes in the ocean, the isotopic composition of phytoplankton was investigated. In-situ plankton were collected by trace metal clean plankton tows from both the Atlantic and Pacific Oceans. In a region close to a continental source of Zn, approximately 300 km off the coast of Brazil (7.4 S, 31.4 W), the isotope composition of the plankton tow material closely resembles that of continental material. The isotopic composition of plankton tows from more remote locations in the open ocean may better record the effects of biological cycling. Additional samples from the Atlantic, as well as samples from the central Pacific near Hawaii and the North Pacific are being processed. This data may be used to better understand how biological processes control the global distribution of Zn isotopes in the oceans.
DE: 4870 Stable isotopes
DE: 4875 Trace elements
DE: 0400 Biogeosciences
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting