Impact of Inorganic Particles of Sedimentary Origin on Global Dissolved Iron and Phytoplankton Distribution.

Iron is known to be the limiting nutrient for the phytoplankton growth over ~40% of the global ocean and to impact the structure of marine ecosystems. Dissolved iron (DFe) is assumed to be the only form available to phytoplankton while the particulate iron (PFe) form has mostly been considered for its role in the biogenic iron remineralization and the induced scavenging. Therefore, most of the studies focused on the nature of DFe external sources to the ocean (i.e. aeolian dust, riverine fluxes, hydrothermal sources and sediment) and their quantification, which still remain uncertain. Among these external sources, the sedimentary sources have been shown to be underestimated. Moreover, the iron supply from sediments has been documented to be often larger in the particle fraction. In our study, we test the impacts of an iron sediment source of inorganic particulate iron (PFe_Inorg) on the global DFe and phytoplankton distribution. We use recent experimentally acquired knowledge to test a parameterization of a PFe_Inorgpool in an ocean global biogeochemical model and compare with published indirect estimation. Depending on the parameterization of its dissolution, the PFe_Inorgcan noticeably enrich water masses in DFe during its transport from the sediment to the open ocean, noticeably in regions not usually accessible to external DFe inputs. Indeed, the fact that DFe is prone to scavenging, reduces the impact of equivalent Fe inputs from sediments in the dissolved form in those regions far from the sediment sources. PFe_Inorgthereby has the potential to fuel the phytoplankton growth in remote offshore regions impacting the coastal-offshore chlorophyll gradient. Sensitivity to model parameters and future experimental work design to better constrain those parameters will be presented.