长江口及其邻近海域颗粒态氨基酸的分布以及对有机质降解和来源的指示

Distribution of particulate amino acids in the Changjiang Estuary and its adjacent sea and their indications for degradation and sources of organic matter

本研究于2018年3月采集长江口及其邻近海域50个站位样品,对颗粒态氨基酸(PAA)的分布与组成进行了分析。结果表明:PAA的平均浓度为(1.86±1.02)μmol/L(0.76~5.55μmol/L),其主要组分为天门冬氨酸(Asp)、谷氨酸(Gly)、丝氨酸(Ser)、丙氨酸(Ala)和甘氨酸(Glu)。颗粒有机碳(POC)和颗粒氮(PN)的平均浓度分别为(74.21±37.70)μmol/L(18.06~238.66μmol/L)和(7.52±3.46)μmol/L(2.27~19.86μmol/L)。PAA、POC与PN具有相似的分布特征,长江口内浓度低于近岸浓度,近岸浓度高于远岸浓度,垂直分布上较为均匀。研究海域中的C/N由近岸向远海逐渐降低,表明陆源输入有机质的影响逐渐降低。基于氨基酸的衍生参数Asp/Gly和Ser+Thr(苏氨酸)[mol%]表明该海域颗粒物中有机质主要源于硅质碳源,与硅藻在该海域中相对较高的生物量有关。碳、氮归一化产率[PAA-C(N)%]以及降解因子(DI)所指示的降解趋势并不完全一致,这或许与PAA-C(N)%和DI适用于不同降解阶段以及氨基酸来源与转化的多样性有关。

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)μmol/L(0.76~5.55μmol/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)μmol/L(18.06~238.66μmol/L)and(7.52±3.46)μmol/L(2.27~19.86μmol/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.