海洋异养细菌利用溶解有机碳的定量评估

Quantification of biodegradable dissolved organic carbon in the ocean

【目的】惰性溶解有机碳(refractory dissolved organic carbon,RDOC)是海洋总有机碳的主体组分,RDOC在深海中可保存数千年,构成了巨大的碳储库,在调节气候变化中有重要作用。但RDOC的定量评估尚未有统一的标准方法。通过测定环境中能被异养细菌利用的溶解有机碳(biodegradable DOC,BDOC)可以反过来评估RDOC的量。本文对BDOC测定中一些关键步骤进行验证,为制定海洋RDOC评估标准奠定基础。【方法】本文评估了3种过滤方式及5种滤膜对DOC测定的影响,并评估了瓶子效应和稀释效应对细菌生长和DOC利用的影响。【结果】研究发现,(1)GF/F滤膜、GF-75滤膜、聚四氟乙烯(PTFE)滤膜(孔径0.2μm)、聚碳酸酯(PC)滤膜(孔径0.2μm)和聚四氟乙烯材质针孔过滤器(HA)(孔径0.2μm)5种滤膜不会引入DOC污染;抽滤过滤和重力过滤方式过滤效果稳定、无污染,而在线过滤效果不稳定,易污染;(2)不同大小培养体系(30–480 mL;表面积/体积比为:1.64–0.67 cm^–1)之间的细菌生长速率和DOC利用量没有显著性差异;(3)培养体系稀释度越高,细菌生长速率越高,对数生长期细菌丰度及DOC利用量越低。【结论】综合考虑,建议BDOC和RDOC测定实验中采用抽滤过滤的方式及不进行稀释的培养体系;常用的滤膜和培养体积对BDOC评估无显著影响。结合研究结果,我们提出了评估海洋RDOC的方法。

[Objective]Refractory dissolved organic carbon(RDOC)is the main component of marine dissolved organic carbon(DOC)pool,which persists in the ocean for thousands of years,and is an important form of marine carbon sequestration.However,there is no consistent protocol for RDOC quantification.RDOC can be quantified by measuring the amount of biodegraded dissolved organic carbon(BDOC).[Methods]We performed quality control experiments to evaluate crucial steps during BDOC quantification,such as the effect of membrane and filtration methods on DOC contamination,and the effect of incubation volume and dilution on DOC utilization.[Results]Results show that(1)GF/F,GF-75,0.2-μm polytetrafluoroethylene,0.2-μm polycarbonate membranes and 0.2-μm polytetrafluoroethylene filter did not induce DOC contamination;the performance of vacuum and gravity filtration were relatively contamination-free and more stable than on-line filtration;(2)incubation ranged 30 mL to 480 mL(area-to-volume ratios:1.64–0.67 cm^–1)showed no significant difference in terms of bacterial growth rate and DOC utilization;and(3)dilution had obvious effects on bacterial growth rate,biomass accumulation,and the amount of the DOC used.[Conclusion]Taken together,it is recommended to use the vacuum filtration and non-diluted incubation in BDOC bioassay;and the commonly used filter membranes and incubation volume may not affect BDOC quantification.Furthermore,we proposed a protocol for measuring RDOC based on this work.