Vertical distribution of bacteria populations at the finfish marine culture in North Bali Coast, Indonesia

Abstract

One of the indicators of aquatic biology is the bacterial population. This study was conducted to determine the vertical distribution of bacterial populations in coastal waters at the marine fish farming in North Bali. Three locations of water samples in depths of 5, 10, 20, and 30 m samples were determined. They are shoreline near the hatcheries at Penyabangan and Gerokgak and water near the net cages at Pegametan Sumberkima. Three replications of the sample collection were done in the surface, middle, and bottom at each sampling point. Samples were collected monthly during the two seasonal transitions from April to June and August to October. The distribution of bacteria was determined by the culture-dependent method (CDM) by measuring the number of bacteria based on bacterial cultivability on agar media. The results showed a lower bacterial population (101-102 cfu/mL) was observed in August. An even distribution of total bacteria (103 cfu/mL) was seen at Pegametan Bay. Higher Vibrio spp. was found at a depth of 10 m than 20 and 30 m. While Pegametan Bay station had the highest Vibrio spp. number. Halotolerant bacteria tend to increase to 5 x 102 cfu/mL from April to June at a depth of 5.