Bacteriological quality of marine recreational water in a tropical environment reflects coastal residential patterns

Abstract

Intestinal enterococci (IE) are the leading cause of marine recreational water impairment especially in the tropical developing countries. Here, the concentrations of IE were empirically determined from marine recreational water along the Dar es Salaam City, in Tanzania, in order to understand the significance of increasing coastal urbanization on the impairment of marine recreational water. IE concentrations determined using a standardized approach were also compared with recreational water quality guidelines (RQG) and occurence of human faecal specific marker (BacHum). IE concentrations across 192 water samples collected between August 2011 and July 2012 varied from <1 to 5 MPN/100 ml, with 29% of samples exceeding regulatory standard. A skewed distribution of IE was observed in which marine water along the coastal environment with high residential density had median IE >102 MPN/100 ml compared to that of marine water along the coastal areas with low residential density (median IE <102 MPN/100 ml). The hypothesis that human faeces were the dominant source of IE in the studied marine water was supported by the fact that sites with IE >102 MPN/100 ml) were positive for BacHum. The fact that marine water along the coastal area with low residential density were devoid of BacHum and their IE concentrations were below RQG implies that they can be used as a reference during restoration of impaired recreational marine water in the studied tropical environment.