北部湾北部海域水体异养细菌的时空分布特征研究

The spatial-temporal distributions of heterotrophic bacteria in seawater of the northern Beibu Gulf

为探讨环境因素对异养细菌丰度的影响,2016年9月至2017年8月通过月度航次调查对北部湾北部海域异养细菌丰度的时空分布特征进行了系统研究。结果表明,调查海区异养细菌丰度介于(2.75～56.86)×10~5 cell/mL,平均值为(11.01±6.31)×10~5 cell/mL。各季节细菌丰度从高至低依次为:夏季、春季、冬季、秋季。异养细菌丰度由近岸海域向西南深水区方向逐渐降低,在近岸浅水区垂直分布均匀,在水深大于20 m的海区出现季节性分层现象:表层细菌丰度较高,底层细菌丰度较低。主成分分析显示温度对异养细菌时空分布有重要影响,秋、冬季异养细菌丰度与温度呈显著负相关,在春、夏季呈显著正相关。细菌丰度与盐度呈显著负相关,说明海水盐度变化是细菌时空分布重要影响因素。异养细菌丰度与叶绿素a和溶解氧含量呈显著正相关,表明浮游植物初级生产过程影响了异养细菌的时空分布。在秋、冬和春3季异养细菌丰度与营养盐水平呈显著负相关,二者关系受浮游植物生物量间接影响。异养细菌时空分布差异取决于环境条件的变化,温度、盐度、叶绿素a和溶解氧含量是影响异养细菌丰度分布的主要因素。

From September 2016 to August 2017, the spatial and temporal distributions of heterotrophic bacteria were studied based on monthly cruise in the northern Beibu Gulf, to reveal their correlation with major environmental factors. The heterotrophic bacteria abundances range in(2.75~56.86) × 10~5 cell/mL, with an average of(11.01±6.31) × 10~5 cell/mL. Generally, they are higher in the summer and spring, while lower in the autumn and winter. Heterotrophic bacteria are densely distributed in the coastal water, and gradually reduce in the southwest offshore. The vertical distribution of heterotrophic bacteria is evenly distributed in the coastal areas, and the seasonal stratification that the surface bacteria abundance is higher and bottom bacteria abundance is lower occurred in sea areas below 20 m. The principal components analysis reveals that the distribution of heterotrophic bacteria is influenced by temperature. The correlations between temperature and heterotrophic bacteria are significantly negative in autumn and winter, while significantly positive in spring and summer. The heterotrophic bacteria abundance correlates negatively with salinity, and positively with chlorophyll a and dissolved oxygen. It suggests that salinity and primary production of phytoplankton affect the spatial and temporal distribution of heterotrophic bacteria. Excluding summer, inorganic nutrients negatively correlate with the heterotrophic bacteria, which is indirectly affected by phytoplankton biomass. Spatial-temporal distributions of heterotrophic bacteria are mainly influenced by temperature, salinity, chlorophyll a and dissolved oxygen.