胶州湾沉积物中氨基酸对有机质降解及细菌源贡献的指示作用解析

基于对胶州湾表层沉积物中总可水解氨基酸（THAA）的含量、组成、构型及分布特征的系统研究,通过氨基酸碳氮归一化产率（THAA-C%,THAA-N%）、降解因子DI、反应活性指数RI以及D型氨基酸占比（D-AA%,摩尔百分比）等指标结合碳氮比（TOC/TN）、碳稳定同位素（δ13C）探析了胶州湾沉积物中有机质的来源与降解状态,利用细菌源有机质及胞外肽酶活性（EEA）探讨了微生物在有机质迁移转化过程中的作用与贡献。结果表明,胶州湾表层沉积物中氨基酸平均含量为（7.60±3.64）μmol/g,在陆源与海源混合影响下,其水平分布呈现湾内高于湾外、湾内东部高于西部的特点,表明湾内东部陆源输入对沉积物THAA具有较高贡献。THAA-C%、THAA-N%、DI、RI以及D-AA%等指示因子均显示胶州湾表层沉积物中有机质的降解程度呈现湾外高于湾内、湾内东部高于西部的变化趋势,有机质来源、微生物活性与上覆水水深共同影响了有机质的降解程度。胶州湾表层沉积物中细菌源有机碳的贡献率为（29.35±18.73）%,其水平分布显示出湾内西部与湾外相近且高于湾内东部的特点。细菌胞外肽酶活性（EEA）平均为（0.81±1.31）nmol/（g·h）（以MCA计）,整体分布趋势与细菌贡献率相反,呈现湾内东部高于湾内西部和湾外的特性。沉积物中有机质的不同海源、陆源占比决定了有机质的可降解性,而有机质的降解程度进一步影响了细菌源有机质的贡献与胞外肽酶活性。

Indications of amino acids for the degradation of organic matter and bacterial sources in sediments of the Jiaozhou Bay

The concentrations, compositions and distributions of total hydrolysable amino acids (THAAs) were investigated in the surface sediments from the Jiaozhou Bay. Combined with the TOC/TN ratios and stable carbon isotope (δ13C), carbon/nitrogen normalized yield of amino acids (THAA-C%, THAA-N%), degradation index (DI), reactivity index (RI) and D-AA% were used to indicate the origin and degradation states of organic matters in the Jiaozhou Bay sediments. Meanwhile, the contribution of bacterial to organic matters and extracellular enzyme activity (EEA) were also used to evaluate the roles of bacterial in the migration and conversion process of organic matters. The result showed that the average content of THAAs in surface sediments of the Jiaozhou Bay was (7.60±3.64) μmol/g. Under the influence of the combination of terrestrial and marine input, the concentrations of THAAs in inner bay were higher than those in outer bay, and THAAs in the eastern area of inner bay was higher than those in western areas, demonstrating the higher contribution of terrestrial input to THAAs in the eastern inner bay. According to THAA-C%, THAA-N%, DI, RI and mol% D-AA, the organic matters in sediments of inner bay were fresher than those in outer bay, and the organic matters in western inner bay area were fresher than those in the eastern area. The sources of organic matter, microbial activity and the depth of seawater column all had impacts on the degradation states of organic matter. The average bacterial contribution to organic carbon in the sediments of Jiaozhou Bay was (29.35±18.73)%, with the higher contribution in the western inner bay and outer bay. The average value of extracellular enzyme activity (EEA) of peptidase was (0.81±1.31) nmol/(g·h), and contrary to bacterial contribution to organic carbon, the EEA had the higher values in the eastern inner bay but had lower values in western inner bay and outer bay. The sources of sedimentary organic matter determined the reactivity of organic matter, and further affected the bacterial contribution to organic matter and EEA of peptidase.