南海北部细菌丰度和细菌生产力分布及其与环境因子相关性

以2014年8月南海北部海水样品为研究对象，利用平板计数法和流式细胞仪计数法对南海北部表层和垂直海域可培养细菌和细菌总数分布状况进行研究，对细菌生产力进行测定，并结合环境因子进行相关性分析。结果表明:珠江口到南海北部海域，水平方向可培养细菌总数变化范围是3.70×102~1.42×103 CFU/mL，细菌总数变化范围是5.12×105~1.61×106 cells/mL，细菌生产力的变化范围是0.03~0.40 mg/m3/h；垂直方向上可培养细菌变化范围是1.08×103~9.00×103 CFU/mL，细菌生产力变化范围是0.01~0.08 mg/m3/h，其中表层海水中的细菌生产力明显高于底层。与环境因子相关性分析表明，水平方向上，影响南海北部表层海水细菌总数和细菌生产力的主要因素是温度、盐度、硝酸盐（NO₃-N）、硅酸盐（SiO₃-Si）、亚硝酸盐（NO₂-N）和磷酸盐（PO₄-P）（P < 0.05）；垂直方向上，影响南海北部可培养细菌总数的主要因素是NO₂-N（P < 0.05），影响细菌生产力的主要影响因素是温度和盐度（P < 0.05）。可见，南海北部表层海水中细菌总数高于可培养细菌总数2~3个数量级，表明该海域表层海水存在大量不可培养细菌；细菌的生命活动在海水表层相较底层更为活跃。

Abundance and production of bacteria and their correlations with environmental factor

Distribution of abundance and production of bacteria and their correlations with environmental factor were investigated, using plate count method and flow cytometry, in the surface and vertical waters of the northern south China sea in August 2014. The cultivable bacterial abundance ranged from 3.70×102 CFU/mL to 1.42×103 CFU/mL, the total bacterial abundance ranged from 5.12×105 cells/mL to 1.61×106 cells/mL and the bacterial productions varied from 0.03 mg/m3/h to 0.40 mg/m3/h in horizontal distribution. In vertical distribution, the cultivable bacterial abundance ranged from 1.08×103 CFU/mL to 9.00×103 CFU/mL and the bacterial productions varied from 0.01 mg/m3/h to 0.08 mg/m3/h, respectively. The correlation analysis results showed that the environmental factors affecting the abundance of total bacteria and bacterial productivity included temperature, salinity, nitrate (NO₃-N), silicate (SiO₃-Si), nitrite (NO₂-N), and phosphate (PO₄-P) (P < 0.05). NO₂-N was the main influencing factor to cultivable bacteria abundance (P < 0.05), while bacterial productivity was highly correlated with temperature and salinity in vertical distribution of northern south China sea (P < 0.05). The total bacterial abundance was 2~3 orders of magnitude higher than cultivable bacteria, suggesting that there were many uncultured bacterium in surface water of northern south China sea and bacterial activities in the surface maybe more active than in the bottom.