Increasing CO<sub>2</sub> Concentration Impact upon Natural Phytoplankton Community at Spermonde Island, Indonesia: Mesocosm Study

Abstract

Ocean acidification is one of an environment problem due to increasing CO 2 concentration. Ocean acidification have shown a negatively impact to marine organisms especially calcifying organisms such as microalgae, coral reef and other invertebrate organisms. Decreasing in carbonate saturation state on the calcification rates of individual species and communities in both planktonic and benthic habitats were occurred due to seawater acidification. The study was conducted at three locations: Barru, Takalar and Barrang Lompo Island using mesocosm technique with two different of incubation periods (48 and 96 hours). Six pCO 2 level based on adding acid base treatments were used, which were 280, 380, 550, 650, 750 and 1000 ppm with 4 replicates In general, alkalinity decreased with increasing CO 2 concentration. However, length of incubation was showed no significant affected to DIC for all CO 2 concentration at Barru and Barrang Lompo mesocosm experiment. PIC and POC showed a varied response between all locations of mesocosms experiment. There was a trend where increasing of POC with increasing of CO 2 concentration. PIC concentration at Barru and Takalar showed a slightl higher at 96 hours than 48 hours of incubation period and for Barrang Lompo mesocosm experiment PIC was higher at 48 hours than 96 hours of incubation period. Chlorophyll a and cell abundance was decresing with increasing CO 2 concentration. Growth, photosynthesis and calcification rate decreased with increasing CO 2 concentration.