STUDY OF IRON SPECIATION IN ANTARCTIC MARINE MATRICES IN RELATION TO CLIMATE CHANGE

Iron (Fe) is the most important trace element in the ocean, as it is required by phytoplankton for photosynthesis and nitrate assimilation, and it is the primary limiting micronutrient in the High Nutrient Low Chlorophyll (HNLC) region across large parts of the Southern Ocean. To understand the availability of this element for organisms, speciation studies have been carried out, which allow to define the chemical species in which the element is distributed. Both temperature and pH influence chemical and biological processes, and could have effects on Fe biogeochemistry and on its speciation. The aim of this work was to determine the concentrations of Fe in polar marine matrices and to study its speciation, focusing in particular on the study of organic ligands able to complex this element. The work focused both on the aspects related to the development of the analytical methods used for these studies, and on the environmental and biological aspects, in order to frame the results obtained in the Antarctic environmental context, by using multivariate analysis methods, such as principal component analysis (PCA), for a better comprehension of the analytical data obtained. Considering the influence of other chemical parameters on iron and its speciation, aspects related to nutrient parameters and the carbonate system were evaluated, and the use of these chemical parameters as possible tracers for Ross Sea water masses was also considered. Particular attention was given to the evaluation of pH considering the effects of ocean acidification and indirectly also on iron speciation, with the development of accurate methods for the assessment of this parameter. Studies were also carried out in Antarctica in the Ross Sea, both for sampling and for on-site measurements in the frame of the ESTRO (Effect of the eaSTern inflow of water on the ROss Sea salinity field variability) project.