THE EFFECT OF ACIDIC POLYSACCHARIDES ON THE BIOGEOCHEMISTRY OF IRONIN THE MARINE ENVIRONMENT

In large areas of the ocean, the so called high nutrient low chlorophyll (HNLC) areas, phytoplankton growth is partly limited by depleted iron (Fe) conditions due to very low Fe input to surface waters. Fe is an important nutrient for marine phytoplankton, being essential in many metabolic reactions. Fast hydrolysis and scavenging onto particles constantly remove Fe from the surface ocean. More than 99% of the remaining dissolved Fe is found to be bound by organic compounds. Photochemical reactions involving dissolved organic matter (DOM) and oxygen form hydrogen peroxide (HOOH). HOOH acts as strong oxidant or reductant in the cycling of organic compounds and trace metals like Fe. The objective of this PhD project was to investigate the role of acidic polysaccharides, main constituents of phytoplankton exudates, on the redox photochemistry of Fe and as Fe ligands.