Abundance assessment of indicator bacteria for coral health in the Pemuteran Waters, North Bali, Indonesia

The increase of anthropogenic land-based activities in the Pemuteran village, a tourist spot in the northern part of Bali Island, threatened the health of its coral reefs. Therefore, this study aimed to assess the impact of anthropogenic activities in the coral reef by using two indicator bacteria (Enterococci and Vibrio). Study sites were chosen based on human activities whereas coral genus was selected following the three most abundant genera in each site. The mucus of coral fragments and the water column overlying the reefs were sampled. These samples were both tested for the presence of Vibrio in TCBS nutrient at 37°C for 24 hours and Enterococci in Slanetz and Bartley nutrient at 41°C for 24 hours. Results showed that the abundance of Enterococci in the mucus of all coral genera were relatively similar, whereas its abundances in seawater were significantly higher than those in mucus. In contrast to Vibrio, the abundances in mucus in all coral genera were significantly higher than those in seawater. Despite the likely relativeness to the natural characteristics of both indicator bacteria, the extremely high concentration of total organic carbon and nitrate in the water column, particularly nitrate, significantly enhance the abundance of Enterococci. The high level of nutrients was detected in the site which has the highest human activities, milkfish culture and marine recreational spot. The abundant of Vibrio may reveal the cause of the high prevalence of coral diseases in this area, whereas Enterococci indicate that anthropogenic pollution has reached its coral reef ecosystem.