Effects of rainfall on the total number of bacteria and the composition of culturable bacteria in Qinhuangdao West Beach

Abstract:

[Objective] To analyze the influence of precipitation on the total bacteria and microbial community composition in coastal waters. [Methods] Water samples were collected from three stations in Qinhuang Dao west beach before and after rainfalls in August 2014. Total and culturable bacterial species were enumerated using fluorescence microscope and plate counting methods, respectively. Culturable bacterial species were identified using molecular approach and the microbial community structure was analyzed. [Results] Total and culturable bacterial species were 5.6×109 cfu/L and 8.3×107 cfu/L before rainfall, 9.2×109 cfu/L and 2.1×108 cfu/L after rainfalls. Among the culturable bacteria, Proteobacteria is the mostly dominant bacterial phylum (80% before rainfall, 73% after rainfall), followed by Bacteroides (12% before rainfall, 13% after rainfall) and Firmicute (7% before rainfall, 11% afer rainfall). Enterobacter spp. (21 strains), Marinobacter spp. (13 strains), Arcobacter spp. (13 strains), Pseudomonas spp. (10 strains), Bacillus spp. (10 strains) and Vibrio spp. (6 strains) were dominant species before rainfall. Enterobacter spp. (22 strains), Marinobacter spp. (21 strains), Bacillus spp. (14 strains), Acinetobacter spp. (11 strains), Pseudomonas spp. (9 strains) and Arcobacter spp. (5 strains) were dominant species after rainfall. [Conclusion] Precipitation has significant impact on total number of bacteria. Clearly, precipitation significantly shaped the bacterial community structure in the coastal waters.

Key words:Beach, Rainfall, Total number of bacteria, Microbial community structure