The bioavailability of riverine dissolved organic matter in coastal marine waters of southern Texas
The bioavailability of riverine dissolved organic matter in coastal marine waters of southern Texas
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DOI：
10.1016/j.ecss.2019.106477
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发表时间：
2019-12
影响因子：
2.8
通讯作者：
Kai Wu;Kaijun Lu;M. Dai;Zhanfei Liu
中科院分区：
文献类型：
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作者：
Kai Wu;Kaijun Lu;M. Dai;Zhanfei Liu
为了研究河流排放到沿海海洋的溶解有机物（DOM）中溶解有机碳（DOC）和氮（DON）的生物可利用性，我们对从德克萨斯州南部五条河流收集的过滤样品进行了一系列为期一个月（24天）的培养实验（拉瓦卡，圣安东尼奥，使命，阿兰萨斯，和Nueces）在2016年夏季（6月）和冬季（1月）期间使用相同的天然沿海微生物组合接种。DOC和DON的生物可利用率（BDOC%和BDON%）在不同的河流和不同的季节变化很大，冬季分别为6-11%和15-38%，夏季分别为0-6%和9-15%。相对较高的BDOC%和BDON%发生在圣安东尼奥和阿兰萨斯河，这是受人类活动的影响更大，通过污水处理厂的排放。从季节上看，冬季河流DOM的生物有效性高于夏季，夏季河流DOM由于底流较低（或停留时间较长）和水温升高而被广泛降解。氨基酸组成的主成分分析进一步证实了冬季DOM降解程度小于夏季。功能基因丰度数据显示，冬季河流DOM相对不稳定，冬季孵化期间N代谢途径和功能基因的增加证明了这一点，而夏季则观察到相反的模式。不同的河流和季节之间的DOM生物利用度的研究结果有重要的影响河流DOM的命运和营养物质供应的潜在贡献，南部得克萨斯州的海湾和河口往往是氮有限的。
To examine the bioavailability of dissolved organic carbon (DOC) and nitrogen (DON) in riverine dissolved organic matter (DOM) discharged to the coastal ocean, we conducted a series of month-long (24 days) incubation experiments with filtered samples collected from five southern Texas rivers (Lavaca, San Antonio, Mission, Aransas, and Nueces) inoculated using the same natural coastal microbial assemblages during summer (June) and winter (January) in 2016. The bioavailable fractions of DOC and DON (BDOC% and BDON%) varied substantially in different rivers and seasons, ranging respectively from 6–11% and 15–38% during winter, and 0–6% and 9–15% during summer. Relatively higher BDOC% and BDON% occurred in the San Antonio and Aransas Rivers, which are impacted more by human activities through discharge from wastewater treatment plants. Seasonally, the riverine DOM was more bioavailable in winter than in summer when DOM may have been extensively degradedin situdue to the low base flow (or long residence time) and the elevated temperature in river water in summer. The principal component analysis on amino acid composition further confirmed that DOM was less degraded in winter than in summer. Functional gene abundance data revealed that winter riverine DOM was relatively labile as evidenced by an increase in N-metabolism pathways and functional genes during the winter incubation, whereas the opposite pattern was observed in summer. The findings of the varying bioavailability of DOM among rivers and seasons have important implications about the fate of riverine DOM and their potential contributions to nutrient supplies as southern Texas bays and estuaries are often nitrogen limited.