South Kalimantan has the potential to develop tourism, one of the place is ex mined diamond in Banjarbaru. The aspects that need to consider in the management and development of tourism are the aspect of cleanliness and safety in freshwater. One of microorganism can determine life in water is plankton. The study determined the community structure of plankton found at ex mined diamond lake Banjarbaru. Sampling was taken from three lakes namely Ceramin, Seran, and Galuh Cempaka with different depths of 0 meters, 3 meters, and 6 meters. Sample of each depth was taken 4 times. The parameters were measured such a temperature, pH, oxygen saturation, brightness, nitrate, phosphate, and Pb. Data were analyzed using SPSS (Statistical Package for the Social Science) for Cluster, Correlation Pearson and Microsoft Excell to calculate diversity index, uniformity, dominance, and importance value. Cluster analysis is used to clasify objects based on same characteristics, Pearson correlation is used to determine correlation between variables. Result showed station 1 consist of 4 phyla, station 2 consist of 4 phyla, and station 3 consist 8 phyla. The importance value of phytoplankton in station 1 all depths are characterictic by Gloeotrichia sp., station 2 by Spirogyra sp., station 3 depth of 0 meters by Spirogyra sp., 3 meters by Scendesmus sp., and 6 meters by Spirulina sp. Importance value of zooplankton in station 1 depths 0 meters by Brachionus urceolaris, depths 3 meters and 6 meters by Brachionus sp. 1, and station 3 at a depth of 3 meters by Mainodaphnia macleayi. Result of Pearson correlation showed there is no correlation between phytoplankton and zooplankton. It showed that zooplankton abudance is more related to another factor (light intensity) than phytoplankton abudance.

Key word: diamond mining, plankton, community structure, importance value