珠江口及海南岛东南海域海水中氨基酸的分布及其对有机物降解指示的研究

Distribution of Amino Acids and Their Indications of Dissolved Organic Matter Degradation in Seawater of the Pearl River Estuary and Hainan Island Southeast Sea

于2021年8月对珠江口及海南岛东南海域海水中的总溶解态氨基酸(THAA)、溶解有机碳(DOC)、有机氮(TN)和叶绿素a(Chl a)的浓度及分布进行了系统的调查研究。结果表明,调查站位海水中THAA的浓度范围为0.68~4.22μmol/L,平均浓度为(1.69±0.98)μmol/L,呈现近岸高、远岸低的分布趋势;垂直分布上,氨基酸浓度均呈现出随深度增加逐渐减小的特征。THAA浓度分布与天冬氨酸(Asp)/β-丙氨酸(β-Ala)和谷氨酸(Glu)/γ-氨基丁酸(γ-Aba)的比值具有显著正相关性,表明细菌活动对THAA的分布以及降解有重要影响。细菌源有机碳对DOC的贡献率约(13.04%±4.50%),呈现出近岸低于远岸、表层高于底层的特征。氨基酸中碳对有机碳的贡献率(THAA-C%)的分布趋势为近岸低于远海,说明近岸站位有机物降解程度更大。降解指数(DI)和活性指数(RI)也和THAA-C%呈现了相似的分布趋势,在调查海域的东部和珠江口近岸海域出现了高值区。垂直方向上,珠江口附近的S8-S14断面底层相对于表层降解因子的值更低,表明底层海水中的有机物降解程度更高,而海南岛东南海域表层降解因子低于底层,底层海水中有机物更新鲜。

The concentrations and distributions of total dissolved amino acids(THAA),dissolved organic carbon(DOC),organic nitrogen(TN)and chlorophyll a(Chl a)in the seawater of the Pearl River Estuary and Hainan Island Southeast Sea were systematically investigated in August 2021.The results showed that the concentrations of THAA in the study area ranged from 0.68 to 4.22μmol/L,with an average of(1.69±0.98)μmol/L.In the vertical distribution,the amino acid concentrations all showed a gradual decrease with increasing depth.Concentrations of THAA positively correlated with aspartic acid(Asp)/β-alanine(β-Ala)and glutamic acid(Glu)/γ-aminobutyric acid(γ-Aba)ratios,indicating that bacterial activity had an important influence on the distribution and degradation of THAA.The contribution of bacterial organic carbon to DOC was about(13.04%±4.50%),showing a lower value inshore than offshore and a higher value in surface layer than in bottom layer.It was found that the distribution trend of contribution of carbon in amino acid to organic carbon(THAA-C%)was lower inshore than offshore,indicating a greater degradation of organic matter at the inshore station.Degradation Index(DI)and Reactivity Index(RI)showed similar distribution trends with THAA-C%,and high value areas were observed in the eastern part of the study area and the inshore waters of the Pearl River Estuary.In the vertical profile,lower values of degradation factor were found at the bottom layer of the Pearl River Estuary in transect S8-S14,indicating that the degradation degree of organic matters in the bottom layer was greater,whereas contrast distribution patterns were found near the Southeast Sea of Hainan Island.