Systematic surveys to examine seasonal variation, degradation, and bioavailability of dissolved organic matter (DOM) in the Changjiang Estuary and the adjacent East China Sea were conducted in July 2016 and February 2017. Concentrations of dissolved organic carbon (DOC) and total hydrolyzable amino acids (THAA) were higher in July than in February. THAA and chlorophyll a (Chl‐a) were positively correlated in July, but not in February. The carbon normalized yields of THAA (THAA‐C%) in surface waters in July and February were not significantly different. However, degradation index (DI) values in the surface water were higher in February than in July. Compared with outer estuary, the inner estuary had lower THAA‐C% and DI values in both surveys. Solar radiation experiments showed that THAA and THAA‐C% values increased with time at station A6‐11 in the oceanic water but declined at C3 in the freshwater, possibly due to the different origins, chemical compositions, or initial degradation states of the DOM at the time of collection. Microbial incubation experiments showed that accumulated DOC and DON in surface waters were bioavailable to the microbial community of the surface layer, but recalcitrant to the microbial fauna from the bottom layer. Leucine (Leu) was selectively consumed, while glycine (Gly), threonine, and alanine appeared to be recalcitrant in summer (July) microbial incubations; and histidine, Gly, and methionine were preferentially consumed, while aspartic acid, serine, phenylalanine, and Leu were recalcitrant in winter (February) incubations.

中文翻译：

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长江口及其邻近东海溶解性有机物的季节变化，降解和生物利用度

系统调查于2016年7月和2017年2月进行，以调查长江口和邻近东海的溶解性有机物（DOM）的季节变化，降解和生物利用度。溶解性有机碳（DOC）和总可水解氨基酸的浓度（THAA）在7月高于2月。THAA和叶绿素一（Chl-一）在7月呈正相关，但在2月却没有。7月和2月在地表水中THAA的碳归一化产量（THAA-C％）没有显着差异。但是，2月份地表水中的降解指数（DI）值高于7月份。与外部河口相比，在两次调查中，内部河口的THAA-C％和DI值均较低。太阳辐射实验表明，海水中THAA和THAA-C％值在A6-11站随时间增加，而在淡水C3处则下降，这可能是由于DOM的起源，化学成分或初始降解状态不同所致。收集时间。微生物温育实验表明，地表水中累积的DOC和DON可被表层的微生物群落生物利用，但从底层对微生物区系有害。在夏天（7月）的微生物培养中，选择性地消耗了亮氨酸（Leu），而甘氨酸（Gly），苏氨酸和丙氨酸似乎是顽强的。在冬季（2月）孵化中，优先使用乙酰氨基葡萄糖和组氨酸，甘氨酸和蛋氨酸，而天冬氨酸，丝氨酸，苯丙氨酸和亮氨酸是顽固的。