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.