9318318 Church Pilot experiments will be performed that will lead the way toward developing polonium and its species as an important marine tracer. These experiments include: (1) defining the volatile species of polonium in laboratory cultures, such as those that are prolific sulfur gas producers, focusing on potential alkylated species, and (2) describing polonium distribution and speciation in productive coastal (salt marshes), (shelf break), and open (for North Atlantic) surface waters, where it is known to be seasonally in excess, and fractionated in biological systems and resulting sedimentary organic material. These experiments will build on existing evidence gathered under a previous NSF sulfur grant. The significance of the experiments should lead the way to future development of polonium as a powerful tracer of carbon cycles in the upper ocean, air-sea exchange of carbon and sulfur based biogases, and carbon fluxes to underlying sediments.