Heterotrophic bacteria of the Dapeng Bay in the South China Sea: community structure, abundance, and the relationships of culturablity with environmental factors

The community composition, abundance and culturablity of heterotrophic bacterioplankton in the Dapeng Bay of the South China Sea were investigated by morphological method, bacterial cultivation and biochemical methods over an annual cycle. Aeromonas and Pseudomonas were the predominant genera among the Gram-negative bacteria. The bacterioplankton abundance fluctuated from 2.07x10(8) to 2.44x10(9) cells/dm(3), and culturable bacteria abundance ranged between 0.1x10(6) and 16.07x10(6) CFU/dm(3). The Culturablity of heterotrophic bacteria ranged between 0.01% and 1.31%. The relationship between bacterial culturablity and the environmental factors was also studied in different sites of the Dapeng Bay. Throughout the bay, a significantly positive relationship was evidenced between bacterial culturability and temperature, meanswhile bacterial culturability was significantly inversely related with salinity. The positive relationship was shown at the central bay while a negative relationship was observed at the bay mouth and there was no significant correlation at top bay between bacterial culturablity and chlorophyll a of sea water. A positive relationship was found between culturability and DIN all the bay, but DIP showed a significantly negative relationship with bacterial culturability only at the mouth of the bay.