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Bridging microbial diversity and chemodiversity of dissolved organic matter to better constrain processes in biogeochemical cycles
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Respiration and carbon dynamics of free-living and particle-attached bacteria in coastal waters of NE Pacific
P-M4-02
Cui Guo* , Ocean University of China
Ying Ke, Hong Kong University of Science and Technology
Hongbin Liu, Hong Kong University of Science and Technology
Presenter Email: guocui@ouc.edu.cn |
| Bacterial respiration (BR) rates are fundamental to understand the role of bacteria in carbon flow in aquatic ecosystem, and therefore it is critical to obtain reliable measurements. Prefiltration- (mostly 0.6-3um) and dark-incubation- (mostly 24 h) based direct measurements of oxygen consumption have been the most commonly used method for BR. However, the prefiltration procedure and long incubation time may cause change of the bacterial abundance and structure, leading to inaccurate measurements. In this study, we assessed the BR method based on oxygen consumption and attempted to correct the error caused by remove of grazers and particle-attached bacteria measuring bacterial abundance, production and respiration of both particle-attached and free-living bacteria at two contrasting site in coastal NE Pacific from Nov 2014 to Mar 2015, we found that the bacterial biomass significantly accumulated after prefiltration during 24-incubation, leading to overestimation of ~11% and 40% of measured BR compared with the corrected in-situ BR of total and free-living bacteria, respectively. The particle-attached bacteria played an important role in the coastal carbon cycle. Although they accounted for ~11% of total bacterial abundance, they contributed to 48% of bacterial production and 28% of bacterial respiration due to their higher metabolic activity. The average bacterial growth efficiency calculated by comparable 24 h integrated bacterial production and respiration was 0.46, with higher value for particle-attached bacteria (0.57) than that of free-living bacteria (0.36). Our results confirmed two major flaws in the current BR methodology and the importance of particle-attached bacteria in coastal ecosystems. |
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