TU Delft: Department Radiation Radionuclides Reactors:
Function PhD student
Phone +31 (0) 15-2787053
Iron chemistry in seawater:
Effects of UV radiation on iron speciation and its availability for phytoplankton
Phytoplankton in the Southern Ocean is the base of the Antarctic food chain, and it also controls the oceanic uptake of carbon dioxide from the atmosphere. This phytoplankton is both iron and (UV) light limited in its growth. For uptake of iron by phytoplankton the different chemical forms in which iron can appear is an important factor. This is also called speciation: the speciation of an atom or molecule is the actual form in which it is present in solution. For example, iron in seawater can be iron hydroxide, colloidal iron, bound to an (in-) organic complex, etc. In the past decade much research has been conducted on the iron chemistry of Southern Ocean seawater. The iron-limited Southern Ocean comprises about 15% of the surface of the planet. However, the iron chemistry of the Southern Ocean is still poorly understood. The aim of this Ph.D. project is to investigate the influence of UV light on the kinetics of iron speciation in seawater in order to understand the uptake mechanism of iron by phytoplankton. The working hypotheses are:
1. the photo reduction of iron (III) to iron (II) is largely driven by UV radiation
2. most dissolved iron in the ocean is kept in solution by organic ligands
3. the bio-availability of iron depends on the kinetics between the different chemical forms of iron
With the use of radioisotopes (55Fe and 59Fe) one specific chemical form of iron can be followed in time. By adding one tracer as iron (III) and one tracer as iron (II) the kinetics of photo reduction can be studied. This method can also be applied to investigate which chemical form is bio-available to phytoplankton.
Sponsors and partners
This research is funded by the Netherlands Society for Scientific Research (NWO) and by the CARUSO project (CARbon Uptake in the Southern Ocean). This project is done in collaboration with the Netherlands Institute for Sea Research (NIOZ) and the University of Groningen (RUG). In situ experiments will be performed in collaboration with the Alfred Wegener Institute (AWI) in Bremerhaven.