ASLO meeting 2023.
Is the iron contained in glacial nanoparticles bioavailable to marine bacterial communities? A Kerguelen island case study.
Thoppil R., R. Zhang, S. Blain, P. Catala, O. Crispi, A. Guéneuguès, B. Marie, I. Obernosterer.
Laboratoire d'Océanographie Microbienne, Banyuls sur mer, France
Biogeochemical processes in the Southern Ocean (SO) are crucial for global ocean balance.Being the largest high-nutrient-low-chlorophyll region, surface waters in the SO hold a large potential for biological activity, in particular carbon dioxide drawdown and the “greening” of the SO. But these biological processes are limited by the essential nutrient iron (Fe). The accelerated melting of glaciers in the SO could be a significant source of Fe but whether this glacial Fe is bioavailable to microorganisms is inadequately understood. Answering such questions is vital for a better understanding of the influence of glacial Fe on marine microbes and their contribution to the carbon cycle. One pathway of interest is siderophores, low molecular weight compounds that can strongly bind to Fe in seawater and thereby render Fe bioavailable. In this study, we provided colloids obtained from lakes that were influenced or not by glacial melt to SO coastal marine microbial communities. Taxonomic profiling displayed significant differences in microbial community compositions between treatments, with known siderophore synthesizers contributing for about half of the relative abundance in incubations amended with glacial-lake colloids. Furthermore, Fe-related gene annotation analyses showed a higher relative abundance of siderophore synthesis and transport genes in these incubations. This indicates that natural bacterial communities can utilize siderophores to access Fe from glacial nanoparticles hence exhibiting different metabolic responses to a novel resource of Fe in the SO.