Determination of iron in seawater

Iron plays an important role in oceanic biogeochemistry and is known to lim it biological activity in certain ocean regions. Such regions have a replet e complement of major nutrients but low primary production of phytoplankton due to low ambient iron concentrations. The determination of iron in seawa ter is a major challenge, although much progress has been made during the l ast two decades. Techniques for total dissolved iron and iron speciation ha ve been developed in order to rationalise its biogeochemical cycling and be tter understand its role in limiting phytoplankton growth. In this paper, a critical review of historical and current analytical methods for the deter mination of iron in seawater is presented and their capabilities evaluated. The need for standard protocols for the clean sampling and storage of low- level (<1 nM) iron seawater in order to maintain sample integrity is emphas ised. The importance of laboratory and shipboard intercomparison exercises to distinguish between environmental variability and operationally measured fractions is also considered. (C) 2001 Elsevier Science B.V. All rights re served.