A Preliminary Survey on the Indigenous Microalgae in a Brackish Water Kakaban Lake, East Kalimantan, Indonesia for Potential Biomass Production

     Brackish water microalgae exploration has been conducted in Lake Kakaban, Indonesia. This study is a preliminary study of a series of microalgae exploration studies that will utilize sustainable microalgae resources, including isolation and collection. The study was conducted in the waters of Lake Kakaban in July 2024 with sampling points in the North (Area 1) and South (Area 2) areas, each with eight stations. Sample collection was carried out using two approaches: fresh samples and samples preserved with 4% formalin. Fresh samples were cultivated in the laboratory with liquid media enriched with KW21 and F2/Guillard (enriched with silica) and cultured under LED lighting in dark: light conditions (12:12). The isolation of microalgae was conducted using an agar plating and a multilevel cell culture. The identification method was done by observing cells under a microscope, which were identified based on the Algae Resource Database and World Register of Marine Species. There were 46 species of microalgae from 10 classes that were successfully identified and dominated by the diatom group from the Bacillarophyceae class (63,04%), green algae (15,2%), Dinoflagellata (13,04%), Golden algae (6,52%) and Euglenophyta (2,17%). Three microalgae species have been successfully isolated and can grow in the laboratory. Of the three isolates, the highest specific growth rate value was obtained in isolate KK1, which was 0.0214 day-1, while in KK3, the SGR value was 0.0206 day-1, and isolate KK9 with an SGR value of 0.0146 day-1 and has the potential for further research development.