Variability in the empirical leucine-to-carbon conversion factors along an environmental gradient
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摘要: 细菌生产力是评价细菌在海洋碳循环中作用的关键参数之一。估算细菌生产力需要亮氨酸与碳转换系数,而该系数在环境中的变化范围很大,由于实测亮氨酸与碳转化系数耗时耗力,很少有研究者现场实测该系数,致使我们对该系数的调控机制的认识相当缺乏。2015年5月至2016年1月期间,我们在珠江口及南海北部近岸海域开展了14个稀释培养实验,以揭示亮氨酸与碳转换系数在该海域的变化特征,探究环境因素对该系数的调控机制。我们发现,亮氨酸与碳转换系数在该海域呈现明显的空间变化特征,该系数在低盐海域(盐度<15)最高1.27-1.69(kg C)/(mol Leu),中盐度海域(15 < 盐度 < 25)次之1.03-1.25(kg C)/(mol Leu),在高盐海域(盐度>25)最低0.48-0.85(kg C)/(mol Leu)。该系数的空间变化受营养物质供应调控,在寡营养海域,细菌生长受营养限制,部分亮氨酸被用于呼吸作用获取能量以保证生存,进而降低了该区域亮氨酸与碳转换系数。因此,准确估算细菌生产力,实测相应亮氨酸与碳转换系数是必不可少的。Abstract: Bacterial production is one of the key parameters to evaluate bacterial role in ocean carbon fluxes. Estimation of bacterial production requires the leucine-to-carbon conversion factors that change widely across environments. However, empirical leucine-to-carbon conversion factors (eCFs) are seldom determined in situ because of time consuming and little is known on regulating factors for the eCFs. During May 2015 to January 2016, fourteen dilution experiments were conducted, from the Zhujiang (Pearl River) Estuary to the coast of the northern South China Sea, to determine spatiotemporal variability in the eCFs and its potential controlling factors along an environmental gradient. The eCFs showed clear spatial variations with the highest (1.27-1.69 (kg C)/(mol Leu)) in low salinity waters (salinity<15), intermediate (1.03-1.25 (kg C)/(mol Leu)) in moderate salinity (salinity of 15-25), and the lowest (0.48-0.85 (kg C)/(mol Leu)) in high salinity waters (salinity>25). Substrate availability was responsible for spatial variability in the eCFs. In the pristine coastal waters, low eCFs was related to substrate limitation and leucine incorporated was respired to maximize the survival rather than bacterial production. Hence, the eCFs measurement was needed for estimating bacterial production accurately in various marine environments.
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Key words:
- bacteria /
- leucine incorporation /
- conversion factors /
- Zhujiang (Pearl River) Estuary
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