Program     Marine pollution, ecotoxicology and sustainability       Poster Distribution of amino acid in DOM and POM in the south china sea. P-E1-08-S Silin Ni* , Li xiaolin,associate professor in Ocean Carbon Group,MEL. Presenter Email: silin.ni@qq.com Labile dissolved organic carbon (LDOC) have a significant influence in the carbon cycle in the ocean. However, as a complex mixture of various matter, DOC can not be directly distinguished by different biological activity. Comparing with other parameters, amino acid is better molecular indicator. The total dissolved concentration,carbon yield and the proportion of special components of amino acid can be more clear and comprehensive indication of DOC biological activity. The biggest problem of researches on amino acid is contamination during each process in the experiment. Therefore, our research spend so much time to adjust each process in the experiment, test method blank with different experimental conditions and finally get good precision,recoveries and reproducibility to guarantee data quality.Samples for particulate hydrolyzed amino acid (PHAA) and total dissolved amino acids (TDAA) were collected during the cruise in June 2018 to the northern South China Sea (NSCS) and West Philippine Sea (WPS) to examine the biological activity of DOC and its transformation when transported from WPS into NSCS through Luzon Strait. The carbon yields to DOC were calculated and patterns of amino acids compositions were quantitatively determined using principle components analysis (PCA). We show that concentrations of TDAA and their yields to DOC decreased from the NSCS continental slope towards the basin area and decreased with depth in the water columns, suggesting a declined trend in biological activity of DOC. The spatial distributions of PHAA presented a similar pattern of TDAA. It is interesting to note that distributions of TDAA and PHAA were impacted by eddies, with addition/removal of nutrients enhanced/inhibited the transformation of DOC.

f7f7f7">