Abstract: This study was conducted to investigate the effects of salinity levels on the sinking, buoyancy, hatching and abnormal rate of fertilized eggs of Eleutheronema tetradactylum under a salinity gradient of 5, 7, 9, 11, 13, 15, 20, 25, 28 (as control), 30, 35, 40, 45. Furthermore, the survival activity index (SAI) of larval E. tetradactylum was observed. The results showed that both fertilized eggs in the stages before the first division and the gastrula sank at salinity below 25, suspended in the central layer when the salinity was 25, and floated at salinity of 28 or more. Fertilized eggs before the first divisions were more sensitive to salinity change than those in the gastrula stage. Survival rate and SAI value of newly hatched larva were significantly impacted by salinity change. Based on hatching rate, abnormal rate of larva and SAI value analysis, it is speculated that the suitable salinity range of E. tetradactylum fertilized egg hatching is 25-35, and the optimum value is 35.

Key words: net primary productivity, carbon stock, mangrove, biomass, litterfall.