Abstract
Analysis of microbe diversity in freshwater resources and nearshore seawater samples of Upolu Island was performed to investigate the distribution of harmful bacteria. For this, 124 samples were collected from 23 river systems, two volcanic lakes, and 45 locations inside and outside the barrier reef of Upolu Island, Samoa. Physicochemical parameters for general water quality, detection of coliform bacteria and 16S rRNA amplicon sequencing were performed on all samples. Fecal indicator bacteria (FIB) testing indicated a wide distribution of coliform bacteria in all sampled freshwater sites with evidence of fecal coliform in most locations. Importantly, evidence of coliform bacteria was found in most seawater samples inside and along the reef, apart from those samples taken ~20 km offshore. Illumina 16S rRNA amplicon sequencing of the V4 hypervariable region confirmed the presence of various types of harmful bacterial species, namely from the Enterobacteriaceae, Enterococcae, Streptococcaceae, and Vibrionacea families. By combining the sensitivity of FIB testing and next-generation sequencing, we were able to show the extent of potential contaminations in fresh and seawater samples and simultaneously identify the potential pathogenic bacterial genera present. The wide distribution of potential harmful bacteria from river runoff or direct sewage dumping has an impact on human health, leading to many skin and intestinal diseases, and is potentially detrimental to coral reef community health.
Highlights
IntroductionAnthropogenically-induced microbial contamination of freshwater resources results in
Anthropogenically-induced microbial contamination of freshwater resources results in~2.2 billion people lacking adequate access to safe drinking water
The pH values ranged from 6.6–8.3 ± 0.1, which is within the guidelines for suitable drinking water [25]
Summary
Anthropogenically-induced microbial contamination of freshwater resources results in. ~2.2 billion people lacking adequate access to safe drinking water. This problem leads to an increasing rate of child mortality and severe diseases [1]. Mixing and accumulation of pathogens in coastal areas is influenced by physical properties. Within protective barrier reefs, such as around Upolu Island, Samoa, water flow and dilution are restricted and, as a consequence, contaminants significantly accumulate, as shown in a recent study on the Great Barrier Reef [4]. Acute infections from direct contact with waters contaminated with microbial pathogens that are able to survive in nutrient-rich fresh and sea waters occur frequently [5]
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