32 nd Symposium of the Malaysian Society for Microbiology (MSM2014) 6-8 December 2014 Terengganu Equestrian Resort (TER), Terengganu, Malaysia Environmental Microbiology 133 RESPONSES OF Chlorella vulgaris (UMT-M1) EXPOSED TO ELEVATED CARBON DIOXIDE Zima, A.N., Fatimah, H. and Hazlina, A.Z. * School of Fundamental Science, Universiti Malaysia Terengganu (UMT), 21030 Kuala Terengganu, Terengganu *Corresponding author’s e-mail: hazlina@umt.edu.my ABSTRACT This study reported on how a microalga, Chlorella vulgaris (UMT-M1) response after exposure to elevated CO2 concentrations. The alga was subjected to a 6h treatment period in which the medium with the alga was aerated with two different CO2 concentrations (i.e. 484 and 968 ppm) and a 24h recovery period in which the CO2 aeration was stopped. pH of the medium, and, algal maximal quantum yield (i.e. Fv/Fm), cell viability, content of hydrogen peroxide (H2O2) and DNA damage were measured. pH of the medium changed from basic conditions (i.e. pH 8.5-8.7) to acidic conditions (i.e. pH 6.0-6.1) after the treatment but changed back to basic conditions (i.e. pH 8.7-8.8) after the recovery. Fv/Fm of the alga was reduced 17-27% after the treatment and was further decreased after the recovery (i.e. 8-13% reduction from after treatment). The number of cells still viable after the treatment reduced to 12-20% of control and was decreasing further with 4-10% after the recovery. The content of H2O2 in the alga was observed to be increased 21-29% after the treatment but dropped 13- 22% after the recovery. Comet assay analysis showed that about 10-12% of the algal cells had their DNA damage lies within the highest level of 4 (i.e. highly damaged) after the treatment. This value was reduced to 8% in 484 ppm CO2 but increased to 24% in 968 ppm after the recovery. In conclusion, C. vulgaris has the potential to be a good biomitigator of CO2 but the abundant CO2 can become damaging to the alga. INTRODUCTION The problem of climate change arising mainly from carbon dioxide (CO2) emission is currently a critical environmental issue. In 2009, for example, Malaysia emitted about 148 million tons of CO2 compared to 117 million tons in 2000 (i.e. 26% increment). The emission of high concentration of CO2 into the atmosphere can cause ocean acidification which poses a threat to the ocean’s food chain. To evaluate the effects, algae can be good bioindicators since they are photoautotrophs, sedentary, easy to identify and are widely distributed in the aquatic ecosystem. They utilize CO2 for photosynthesis which can be useful in CO2 mitigation. CO2 fixation by the algae can be combined with production of biomass which can be burned for heat and electricity. Moreover, algae are known to be able to adapt to harsh environments by inducing protective mechanisms which can be beneficial as mitigation or bioindicator tools. Although algae cultivation has been practiced in Malaysia, its environmental benefit has not been realized to the full extent. The aim of this study is to have a general overview on the