Mariculture is overgrowing along with the decrease in a marine catch. It is expected to be the largest supplier of marine and fishery sectors. Improvement effort of mariculture activities will be further encouraged including efforts to optimize its other roles as conservation areas. This study is conduct in Barru waters from February 2017 to November 2018. The purpose of this study is to determine biodiversity, density, dominance and how long marine organism used mariculture area as their place to live in. Methods used for this study was observation at the mariculture’s site, and then the unidentifiable samples would be taken to the laboratory for further identification. The conclusion of the study are 1) The composition of the phytoplankton found in Barry's waters is from the diatom class (Bacillariophyceae) consisting of 29 species and Cynophyceae that included of 4 species. Zooplankton dominated by crustacean class composed of 10 species, and other species is from Cirripediaclass, which only found one species. 2). The value of the diversity index obtained for phytoplankton was about 2.42 – 2.82 and the highest at station II (floating net cage location) that is 2.82. For the zooplankton which only found at seaweed had a diversity index of 2.26. This indicated that the species composition and abundance of plankton depend on the conditions of the aquatic environment. The uniformity index for phytoplankton is around0.82 – 0.94 and the highest value found at station II is 0.94. Uniformity index for zooplankton with a value of 0.94 indicated that the cost tends to be stable

Keywords: biodiversity, abundance, plankton, mariculture, organism