Program     Marine Carbon Sequestration (MARCO): Multiscale Regulation and Response to Global Change       Poster Physiological and molecular responses of trichodesmium erythraeum IMS101 involved in acclimatization to iron deficiency P-SPS5-09-S Ran Duan* , State Key Laboratory of Marine Environmental Science (Xiamen University), China Presenter Email: 178416430@qq.com Trichodesmium is one of the vital cyanobacterial taxa responsible for nitrogen fixation in the oligotrophic tropical and subtropical oceans where iron concentrations are extremely low. While it has been reported frequently on Trichodesmium physiology and ecology under iron limited conditions, the changes in cellular and molecular responses of Triochodesmium across an iron concentration gradient are less known. In order to better understand the dynamics involved in Trichodesmium acclimatization to iron stress, we cultivated Trichodesmium erythraeum IMS101 in medium prepared with the South China Sea surface water supplemented with different concentrations of iron. We measured a suite of physiological parameters, such as chlorophyll a-derived specific growth rate, photochemical efficiency, rate of nitrogen and carbon fixation etc., and conducted gene expression analysis of the iron stress indicator genes (idiA and isiA) using the real-time quantitative PCR technique. Our data reveal the differential growth rates, productivities and gene expressions of Trichodesmium corresponding to the iron concentration gradient. This study has implications in understanding the core physiological and molecular responses involved in Trichodesmium acclimatization to the rapidly changing ocean.