The Effects of Ultrasound Application on Green Algae Chlorella variabilis Harika Eylül Esmer 1, Figen Esin Kayhan 1, Cenk Sesal 1, Turgay Çakmak 2, Barış Gökalsın 1 1 Department of Biology, Faculty of Sciences and Arts, Marmara University, Istanbul 34722, Turkey 2 Department of Molecular Biology and Genetics, Istanbul Medeniyet University, Istanbul 34730, Turkey 30 min 60 min 90 min 120 min 5 min 15 min Abstract: Algae growth is the common problem in the water treatment plants and water reservoir. Algal blooms can cause release of toxins which in high concentrations are a serious health hazard for humans and animals. To find bloom control methods which are green that is to consume little energy, reduce water treatment costs and chemical use in water treatment, is a challenge. Ultrasonic technology as an innovative technology may be used for water and wastewater treatment for pollution removal. The results indicate that ultrasound may provide a more environmentally friendly and more effective method for the control of this bloom. In the present study ultrasound applied at a frequency of 60 kHz for durations of 5–120 min to Chlorella variabilis culture. Our results especially for the longer exposure times, between control and experiment groups, were more pronounced. Keywords: Ultrasound, Green Algae, Chlorella variabilis, Eutrophication, Water treatment Materials & Methods: Ultrasound works by the phenomenon of acoustic cavitation which occurs after sound waves above the frequency of 20 kHz are passed through a liquid medium (Suslick, 1990; Leighton, 1994). Cavitation is the phenomena of the formation, growth and collapse of microbubbles or cavities occurring in extremely small interval of time (milliseconds) in a liquid (Shah et al., 1999). In this study, ultrasound applied at a frequency of 60 kHz for durations of 5–120 min to 300ml Chlorella variabilis culture, which was cultivated in BG11 medium. Chlorella variabilis was obtained from microalgae laboratory of Medeniyet University. Algae shapes was observed with fluorescent microscopy. References : - Burkholder, J.M., Gilbert, P.M. & Skelton, H.M. (2008) Mixotrophy, a major mode of nutrition for harmful algal species in eutrophic waters. Harmful Algae, 8, Burrini, D., Lupi, E., Klotzner, C., Santini, C. & Lanciotti, E. (2000) Survey for microalgae and cyanobacteria in a drinking-water utility supplying the city of Florence, Italy. Journal of Water Supply Research and Technology AQUA, 49, Harper, D. (1992). Prediction and modelling of the causes and effects of eutrophication. Eutrophication of freshwaters— Principles, problems and restoration, Harper, D., Eds.; Chapman & Hall: London, 167– Lee T.J., Nakano K., Matsumura M A novel strategy for cyanobacterial bloom control by ultrasonic irradiation. Water Science and Technology, 46: Leighton T.G. (1994). The Acoustic Bubble. Academic Press, San Diego, USA - Shah YT, Pandit AB, MoholkarVS Cavitation Reaction Engineering. Plenum Publishers, USA - Suslick, K.S. (1990) Sonochemistry. Science, 247, Introduction : Algae are photosynthetic organisms that are common in the environment and they are an integral part of an aquatic ecosystem with recycling nutrients (Burkholder et al., 2008). An algal bloom is a natural phenomenon that appears in eutrophic conditions. Eutrophication is defined as the accumulation of the nutrient occurring in a water source. Nitrogen and phosphorus are the main nutrients required for blooming cases of algae (Harper, 1992). Eutrophication of water sources has escalated in recent years due to anthropogenic effects (Burrini et al., 2000). Chemical treatments are recently being used to clean eutrophic lakes but such treatments are expensive and cause secondary pollution in the environment. Ultrasound usage was classified as a non-chemical and economical strategy to control algal growth. Ultrasonic control mechanisms that was reported may be consist of: production of free radicals, disruption of gas vesicles and inhibition of photosynthesis (Lee et al., 2002). Results & Conclusion: This study tries to investigate the efficiency of ultrasonic treatment of 60kHz and 100W on algae. In the fluorescence microscopy images, disrupted cells give lower or no fluorescence due to dispersion of chlorophyll. In conclusion, the results indicate that disruption of algae increases accordingly with application time. Extensive future research is required to scrutinize the effects of ultrasonic irradiation on algal disruption at different energy inputs and longer sonication times. International Conference on Applied Biological Sciences (ICABS), September 2015 Skopje/ Macedonia