This is an investigation of the cycling and speciation of germanium, selenium, arsenic, and antimony in the Black Sea, the world's largest permanently-anoxic marine basin. The PI's will obtain detailed depth profiles of dissolved and suspended particulate speciation (oxidation states and organic forms) through the oxic, suboxic, and anoxic zones of the water column, and in the underlying sediment and pore waters. This comprehensive data set will clarify the roles of marine aerobic/anaerobic metabolism and particulate scavenging on the redox behavior, speciation, and concentration of metalloid elements. Time scales of processes will be deduced from data generated by other groups on the same expedition (e.g., water circulation: T/He;/ 14C; Fe/Mn oxidation-reduction and scavenging rates; microbial activity). The Black Sea is an ideal environment for this work because its anoxic waters have a long residence time (ca. 1000 yrs.) and are in quasi-steady state, and because of the intense and well-defined iron and manganese cycling in the vicinity of the oxic/anoxic interface.
