WATER QUALITY OF LAKE MANINJAU, WEST SUMATERA, AND POTENTIAL OF INDIGENOUS BACTERIA TO REDUCE PHOSPHATE CONCENTRATION IN THE LAKE

• Main Author: Nurul Sukma, Hastari
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/71048
• Institution: Institut Teknologi Bandung

Lake Maninjau is located in West Sumatra province and is one of the multifunctional lakes in Indonesia, used for fishery activities by cultivating floating net cages. The cultivation of floating net cages has become a problem in Lake Maninjau because it increases the nutrient content, especially phosphorus. Based on the Presidential Regulation of the Republic of Indonesia number 60 of 2021 regarding saving national priority lakes, Lake Maninjau is one of 15 national priority lakes. Several previous researchers have carried out efforts to restore water quality, one of which is the bioremediation method. In the bioremediation method, degrading bacteria isolated from the environment (indigenous bacteria) can be used. The purpose of the research was to compare the characteristics of the physical and chemical factors of the waters around the floating net cage location (hereinafter referred to as the KJA location) and the location without floating net cages (Non- KJA); comparing the abundance of bacteria in KJA and Non-KJA; isolate bacteria that can reduce phosphate content; and tested the activity of phosphateaccumulating bacteria isolates to reduce phosphate concentrations in Maninjau Lake, Agam Regency, West Sumatra. Measurement of physical and chemical factors carried out, among others, total phosphate, total nitrogen, brightness, temperature, oxygen solubility, and acidity level (pH). Analysis of total bacteria around KJA and non-KJA in the waters of Lake Maninjau was carried out using the Total Plate Count (TPC) method on Nutrient Agar media. Phosphate-accumulating bacteria were isolated using beef extract media, yeast glucose extract (YG) medium, and Luria–Bertani (LB) medium. Total phosphate-accumulating bacteria were analyzed using the Total Plate Count (TPC) method in YG media. The analysis carried out included analysis of bacterial abundance, analysis of the abundance of phosphate-accumulating bacteria, analysis of trophic status scores, analysis of the dominance index of phosphate-accumulating bacteria, and analysis of the activity of isolates of phosphate-accumulating bacteria. The decrease in phosphate concentration was determined by calculating the ratio of the initial phosphate concentration and the final phosphate concentration. Identification was carried out on the dominant bacteria in YG media which had the potential to reduce phosphate concentrations. Analysis of trophic status scores shows total phosphate parameters indicated that KJA and Non-KJA areas in hypereutrophic condition, and total nitrogen parameters indicated KJA and Non-KJA areas in oligotrophic to eutrophic conditions. Analysis of bacterial abundance showed that the number of bacteria in the KJA (1,30x106 CFU/mL, 1,45x106 CFU/mL, 1,60x106 CFU/mL) location was higher than the number of bacteria in the Non-KJA (1,30x106 CFU/mL, 1,45x106 CFU/mL, 1,60x106 CFU/mL) location with a significance value of 0.015. The calculation of the dominance index on the isolated bacteria resulted in a value of 0.54, indicating a dominant species from the isolated sample. The results of the identification of the dominant species of phosphate-accumulating bacteria showed morphological and physiological similarities with Citrobacter sp. potential to reduce the concentration of phosphate in the media. Testing on the activity of Citrobacter sp. showed that the bacteria Citrobacter sp. is effective to reduce the concentration of phosphate in phosphate enriched media as much as 72.5% to 97.5%. Optimum conditions for Citrobacter sp. to work are with the addition of 3% inoculum, pH 7.2-8, and the initial concentration of phosphate as much as 8.90 mg/L. This study showed that Maninjau Lake experienced an excess of phosphate from KJA activities. The research data showed that the bacteria isolated from the waters of Lake Maninjau had the potential to reduce the concentration of phosphate.