Distribution of particulate amino acids in the Changjiang Estuary and its adjacent sea and their indications for degradation and sources of organic matter
A total of 50 samples were collected to investigate the distribution and composition of particulate amino acids(PAA)in the Changjiang Estuary and its adjacent East China Sea in March, 2018. The results showed that the average concentration of PAA was(1.86 1.02)mumol/L(0.76~5.55 mumol/L). The major components of PAA in this study were Asp(aspartic acid), Gly(glycine acid), Ser(serine acid), Ala(alanine acid)and Glu(glutamic acid). The average concentrations of particulate organic carbon(POC)and particulate nitrogen(PN)were(74.21 37.70)mumol/L(18.06~238.66 mumol/L)and(7.52 3.46)mumol/L(2.27~ 19.86 mumol/L), respectively. The distributions of PAA, POC and PN showed similar trends, with elevated concentrations were found at the mouth of the Changjiang River and nearshore stations of the study area. The vertical distributions of PAA, POC and PN exhibited a uniform pattern. The C/N ratio in this study gradually decreased seaward, reflecting the influence of terrestrial input. Derivative parameters Asp/Gly and Ser + Thr [mol%] based on amino acids indicated that POM was dominated by diatomaceous organic matter, which might be due to the dominant growth of diatoms in the study area. No correlation were found between the PAA-C(N)% and the degradation index(DI), respectively. This discrepancy may be related to the application of PAAC(N)% and DI to different stages of degradation and the diversity of sources and transformations of amino acids
