Deep-Sea Research II 48 (2001) 2933–2945 Silver in the western equatorial and South Atlantic Ocean K. Ndung’u*, M.A. Thomas, A.R. Flegal Environmental Toxicology, WIGS University of California, Santa Cruz, Santa Cruz, CA 95064, USA Abstract Vertical profiles of total dissolved (50.22 mm) silver concentrations in the equatorial and southwest Atlantic Ocean provide a new perspective on the processes controlling the element’s external fluxes and internal biogeochemical cycling in the World Ocean. Atmospheric inputs of natural and/or industrial aerosols appear to elevate silver concentrations in remote surface waters in the South Atlantic, where silver is effectively scavenged onto and/or bioaccumulated by plankton. The subsequent remobilization of silver with depth is relatively coincident with that of silicate, suggesting much of that silver is sequestered within a refractory organic phase associated with biogenic silica. That silver is then remineralized, and appears to be conservatively transported in subsurface water masses throughout the World Ocean. # 2001 Elsevier Science Ltd. All rights reserved. 1. Introduction Resolution of the global biogeochemical cycle of silver in the World Ocean is progressing with the acquisition of vertical (0 to >5000m) concentration profiles of silver from 338Sto88N in the Atlantic Ocean. The profiles were determined during the Third Intergovernmental Oceanographic Commission (IOC III) Global Investigation of Pollutants in the Marine Environment (GIPME) baseline survey in 1996 (Cutter and Measures, 1999). These profiles were preceded by vertical concentration profiles of silver in the two prior IOC cruises (Flegal et al., 1995; Rivera-Duarte et al., 1999) in the eastern tropical Atlantic (IOC I) and in the high-latitude North Atlantic (IOC II), as well as by the initial measurements of silver in vertical profiles in the South Pacific (Murozumi, 1981) and North Pacific (Martin et al., 1983). Consequently, there now is a diverse, albeit small, set of preliminary measurements of dissolved silver concentrations in the World Ocean. Those preceding analyses indicated that silver is distributed as a recycled element, with relatively low concentrations (52 pM) in remote surface waters. The apparent enrichment of *Corresponding author. E-mail address: kndungu@es.ucsc.edu (K. Ndung’u). 0967-0645/01/$-see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII:S0967-0645(01)00025-X