The Community Structure of Microalgae and Exploring its Potentially to Biofuel Producing in Ranu Grati, East Java Indonesia

Abstract Microalgae are microscopic autotrophic organisms which act as one of the biofuel-producing organisms. Ranu Grati is one of the volcanic lakes located in Pasuruan, East Java. Human activities around the waters are responsible for eutrophication of the water quality. The aim of this study was (1) described the profile of water quality and microalgae community structure, and (2) investigated microalgae potential as a producer of biofuels based on lipid content. Explorative research was carried out by taking a sample of water at a depth of 50 cm at 5 stations. Water quality parameters measured were DO, pH, BOD, TP, and TKN. Microalgae samples were taken by filtering 3 L of water using Plankton Nets. Plankton samples were identified and calculated using Haemocytometer. Furthermore, microalgae abundance, Important Value Index (IVI), diversity index, richness taxa, Evenness, and Richness index were determined. Species with the two highest IVI was determined the lipid levels use literature. The results showed that the waters of Ranu Grati had been contaminated with high organic matter (BOD levels 8.30-8.72 mg/L) with trophic status classified as mesotrophic to hypertrophic (TP 0.05-0.08 mg/L and TKN 0.23-0.32 mg/L). DO levels was high and have a range value 7.47-9.87 mg / L, while range of pH value 8.73-9.07. There were found 18 species of microalgae with varied 10-18 species in each station. Pollution status of Ranu Grati based on Shannon Wiener diversity index categorized as moderately polluted with range values 1.95-2.34. Value of microalgae evenness 0.77-0.86 indicated high uniformity with equally even distribution of species. Chlorella sp. and Scenedesmus sp. have the highest IVI and have a potential to produce biofuel with lipid levels 28 -32% (dry weight) and 12-14% (dry weight) respectively.