Program
 
General Session 3: Biological oceanography & global change
 
 
 
Poster
Dynamics of carbon metabolism of free-living and attached bacteria at two contrasting subtropical coastal sites
GS3-20-S
Ying Ke* , Hong Kong University of Science and Technology
Cui Guo, Hong Kong University of Science and Technology
Shuwen Zhang, Hong Kong University of Science and Technology
Yan Fei Yeung, Hong Kong University of Science and Technology
Hongbin Liu, Hong Kong University of Science and Technology
Presenter Email: yke@connect.ust.hk
Bacterial respiration (BR) and bacteria production (BP) rates are fundamental to understand the role of bacteria in carbon flow in aquatic ecosystem. In our study, bacteria abundance, respiration and production of both free-living (FL) and particle-attached (PA) bacteria at two contrasting subtropical coastal sites were measured. The western estuarine station (WE) is influenced by freshwater discharge of Pearl River and has a high level of nutrients, whereas the eastern oceanic station (EO) is affected mainly by the South China Sea and has limited nutrients. We found that station WE had higher overall BP and BR than station EO. BP and BR at station WE peaked at June and August respectively, during which months the salinity was the lowest of the year. At station EO, BP and BR were constantly high from July to October and relatively low from November to March. This indicates that while BP and BR at both sites were highly controlled by temperature, those rates at station WE were also largely influenced by Pearl River discharge. Although BP and BR were high in summer, bacterial growth efficiency (BGE) at both sites was very low in August, possibly a result of stronger temperature dependence of BR than that of BP. Interestingly, although PA bacteria accounted for only ~10.5% (¡À7%) and ~9.4% (¡À4.8%) in total bacteria abundance at WE and EO, respectively, they contributed to ~49% (¡À19%) and ~46% (¡À24%) of BP. The cell specific BP of PA bacteria was 16 times higher than that of FL bacteria at both sites, indicating that PA bacteria are more metabolic active than that of FL bacteria. We also observed that PA bacteria had a higher contribution to total BP in January and February than March to August. Our results revealed differences in bacteria activity between estuarine and oceanic stations and emphasized the contribution of PA bacteria.