Laboratory of Microbial Ecology, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
Appl Environ Microbiol. 2009 Dec;75(24):7594-601. doi: 10.1128/AEM.01227-09. Epub 2009 Oct 9.
We investigated the temporal variation of bacterial production, respiration, and growth efficiency in the tropical coastal waters of Peninsular Malaysia. We selected five stations including two estuaries and three coastal water stations. The temperature was relatively stable (averaging around 29.5 degrees C), whereas salinity was more variable in the estuaries. We also measured dissolved organic carbon and nitrogen (DOC and DON, respectively) concentrations. DOC generally ranged from 100 to 900 microM, whereas DON ranged from 0 to 32 microM. Bacterial respiration ranged from 0.5 to 3.2 microM O2 h(-1), whereas bacterial production ranged from 0.05 to 0.51 microM C h(-1). Bacterial growth efficiency was calculated as bacterial production/(bacterial production + respiration), and ranged from 0.02 to 0.40. Multiple correlation analyses revealed that bacterial production was dependent upon primary production (r2 = 0.169, df = 31, and P < 0.02) whereas bacterial respiration was dependent upon both substrate quality (i.e., DOC/DON ratio) (r2 = 0.137, df = 32, and P = 0.03) and temperature (r2 = 0.113, df = 36, and P = 0.04). Substrate quality was the most important factor (r2 = 0.119, df = 33, and P = 0.04) for the regulation of bacterial growth efficiency. Using bacterial growth efficiency values, the average bacterial carbon demand calculated was from 5.30 to 11.28 microM C h(-1). When the bacterial carbon demand was compared with primary productivity, we found that net heterotrophy was established at only two stations. The ratio of bacterial carbon demand to net primary production correlated significantly with bacterial growth efficiency (r2 = 0.341, df = 35, and P < 0.001). From nonlinear regression analysis, we found that net heterotrophy was established when bacterial growth efficiency was <0.08. Our study showed the extent of net heterotrophy in these waters and illustrated the importance of heterotrophic microbial processes in coastal aquatic food webs.
我们研究了马来西亚半岛热带沿海水域中细菌生产力、呼吸作用和生长效率的时间变化。我们选择了五个站位，包括两个河口和三个沿海站位。温度相对稳定（平均约 29.5°C），而河口的盐度变化较大。我们还测量了溶解有机碳和氮（DOC 和 DON，分别）浓度。DOC 一般在 100 到 900 微摩尔之间，而 DON 在 0 到 32 微摩尔之间。细菌呼吸作用在 0.5 到 3.2 微摩尔 O2 h(-1)之间，而细菌生产力在 0.05 到 0.51 微摩尔 C h(-1)之间。细菌生长效率计算为细菌生产力/(细菌生产力+呼吸作用)，范围在 0.02 到 0.40 之间。多元相关分析表明，细菌生产力取决于初级生产力（r2 = 0.169，df = 31，P < 0.02），而细菌呼吸作用取决于基质质量（即 DOC/DON 比）（r2 = 0.137，df = 32，P = 0.03）和温度（r2 = 0.113，df = 36，P = 0.04）。基质质量是调节细菌生长效率的最重要因素（r2 = 0.119，df = 33，P = 0.04）。利用细菌生长效率值，计算出的平均细菌碳需求为 5.30 到 11.28 微摩尔 C h(-1)。当将细菌碳需求与初级生产力进行比较时，我们发现只有两个站位存在净异养。细菌碳需求与净初级生产力的比值与细菌生长效率显著相关（r2 = 0.341，df = 35，P < 0.001）。通过非线性回归分析，我们发现当细菌生长效率<0.08 时，净异养就会出现。我们的研究表明了这些水域中净异养的程度，并说明了异养微生物过程在沿海水生食物网中的重要性。
