Dissolved iron at subnanomolar levels in the Southern Ocean as determined by ship-board analysis

The biogeochemistry of iron was investigated in remote waters of the Antarc tic ocean in the austral summer of 1995/1996. A sensitive flow injection an alyser, based on in-line preconcentration and luminol chemiluminescence det ection (FIA-CL), was used for underway surface measurements and vertical pr ofiling during a fine scale survey in the Polar Front (PF) in the Atlantic sector of the Southern Ocean. Results indicated a dynamic environment with dissolved iron concentrations ranging from 0.05 to 0.3 nM. Distributions ar e consistent with chlorophyll a and fCO(2) suggesting a coupling with these parameters. The highest iron concentrations (0.3 nM) were found where chlo rophyll a abundance was highest and CO2 undersaturation the most pronounced . The vertical distribution (upper 500 m) revealed a nutrient type distribu tion with low subsurface values (0.1 nM) gradually increasing to similar to 0.3 nM at depth. (C) 1998 Elsevier Science B.V. All rights reserved.