Objective To investigate the fluctuation patterns of water quality and impact factors of microbial indicators in a bathing beach of Hainan, and to provide a basis for environment supervision in bathing beaches.
Methods Water samples were collected at a nearshore spot, a spot with the highest density of swimmers, and a spot with the remotest distance in the bathing beach, respectively, once a week, from May to November of 2013-2014. A total of 162 water samples were collected to detect precipitation, water temperature, transparency, dissolved oxygen, and fecal coliforms (FC). In June (wet season) and October (level season) 2014, 18 sediment samples were collected at supratidal, intertidal, and subtidal zones nearshore, respectively, to detect FC and Enterococcus (EC). Analyses included t-test, analysis of variance, and Pearson correlation analysis.
Results The water quality of the bathing beach was graded as excellent in 2013 and 2014, and it was even better in 2014 than in 2013. The FC for 2013 and 2014 was (108.1±67.2) and (64.4±20.8) cfu/L respectively. The transparency was (7.95±2.52) and (9.49±0.92) m respectively. The dissolved oxygen at nearshore spot was lower than that at the densest spot (P=0.019) and the remotest spot (P=0.049). In wet season the transparency was greater than that in level season (P < 0.001). FC was negatively correlated with transparency (r=-0.381, P < 0.001) and dissolved oxygen (r=-0.235, P < 0.001), but irrelevant with water temperature and real-time rainfall (P>0.05). Higher levels of FC and EC were found in supratidal sediment, which were 19 000 and 300 cfu/kg respectively.
Conclusion The water quality of the bathing beach is improved. Transparency could indicate microbial contamination of water. However, higher FC and EC levels are detected in supratidal sediment, and great attention should be paid to monitoring microbial contamination in sediments and sands.
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