Anthropogenic contamination in Red Sea and their potential impact on marine water microbial community

Good water quality in the Red Sea is imperative for the continued sustenance of key industries like desalination and aquaculture, as well as to ensure minimal public health impact. Through the use of next-generation sequencing, this study aims to evaluate the impact anthropogenic contamination has on seawater microbiota at four sampling zones of near-shore water (<1.5km from the coast) and from two swash zones of local beaches. Conventional water quality parameters relating to nutrient content and enterococci numbers were also monitored. Occasional breaches in the enterococci numbers (> 35 MPN/100ml) and significantly higher abundance of genera associated with opportunistic pathogens were detected in the water samples collected from swash zones of beaches. Total organic carbon (1.48-2.18 mg/L) and nitrogen (0.15-0.27 mg/L) content in these water samples were also significantly higher than that detected in the near-shore waters (1.13 mg/L for organic carbon and 0.09 mg/L for total nitrogen). The abundance of certain genera, for example Clostridia group, was observed to correlate with the nutrient content (Spearman’s rank > 0.503). Furthermore, Enterococcus faecalis and E. faecium isolated from the beach sands showed resistance to up to 5 types of antibiotics (i.e., kanamycin, erythromycin, chloramphenicol, ceftazidime and meropenem). OTUs associated with cyanobacteria, Prochlorococcus and Ostreococcus were more prevalent in the near-shore waters collected in closest proximity to a sewage outfall. Microbial richness at these sites was on average 702 OTUs, and was significantly lower than the average 1062 OTUs determined from all other samples. Our findings suggest that anthropogenic contamination arising from sewage discharge and recreational activities resulted in different extent of perturbations on marine water community in near-shore and swash zones of the Red Sea.