Response of Bacterial Metabolic Activity to the River Discharge in the Pearl River Estuary: Implication for CO2 Degassing Fluxes
Response of Bacterial Metabolic Activity to the River Discharge in the Pearl River Estuary: Implication for CO2 Degassing Fluxes
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DOI：
10.3389/fmicb.2019.01026
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发表时间：
2019-05
影响因子：
5.2
通讯作者：
Xiangfu Li;Jie Xu;Zhen Shi;Ruihuan Li
中科院分区：
文献类型：
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作者：
Xiangfu Li;Jie Xu;Zhen Shi;Ruihuan Li
在丰水期（2015年5月）和枯水期（2016年1月），同时测定了珠江口（PRE）不同环境梯度下的细菌产量（BP）、呼吸（BR）和生长效率（BGE），以考察细菌对PRE中河流溶解有机碳（DOC）的响应。珠江排放的挥发性溶解有机质（DOM）具有较低的DOC:DON比，导致DOC浓度和DOC:DON比有明显的梯度。BP （3.93 ~ 144 μg C L−1 d−1）比BR （64.6 ~ 567 μg C L−1 d−1）在PRE中随环境梯度变化更大。随着河流DOC的输入，BP和细胞特异性BP均升高；相比之下，细胞特异性细菌呼吸下降，可能是因为不稳定的河流DOC减轻了细胞维持的能量成本。因此，细菌呼吸的增加比预期的要少。我们的研究结果表明，高生物利用度的河流DOC的输入改变了合成代谢和分解代谢途径之间的碳分配，从而降低了浮游细菌用于细菌呼吸的DOC的比例。这可能是PRE接收大量污水DOC的低CO2脱气的潜在机制之一。
Bacterial production (BP), respiration (BR) and growth efficiency (BGE) were simultaneously determined along an environmental gradient in the Pearl River Estuary (PRE) in the wet season (May 2015) and the dry season (January 2016), in order to examine bacterial responses to the riverine dissolved organic carbon (DOC) in the PRE. The Pearl River discharge delivered labile dissolved organic matters (DOM) with low DOC:DON ratio, resulting in a clear gradient in DOC concentrations and DOC:DON ratios. BP (3.93–144 μg C L−1 d−1) was more variable than BR (64.6–567 μg C L−1 d−1) in terms of the percentage, along an environmental gradient in the PRE. In response to riverine DOC input, BP and the cell-specific BP increased; in contrast, the cell-specific bacterial respiration declined, likely because labile riverine DOC mitigated energetic cost for cell maintenance. Consequently, an increase in bacterial respiration was less than expected. Our findings implied that the input of highly bioavailable riverine DOC altered the carbon portioning between anabolic and catabolic pathways, consequently decreasing the fraction of DOC that bacterioplankton utilized for bacterial respiration. This might be one of the underlying mechanisms for the low CO2 degassing in the PRE receiving large amounts of sewage DOC.