Biodiversity of benthic fauna was high in the seagrass ecosystem in Kung Krabaen Bay even though the bay’s coast had many intensive shrimp farms. Halodule pinifolia and Enhalus acoroides were two species of seagrasses distributed widely in the bay. Their biomass was higher in summer than in the rainy season. 27 families of polychaetes and 10 species of gastropods were predominantly distributed in the seagrass beds and their biodiversity indices were not different among transects (North, East, South). At the same time, 18 species of bivalves were distributed among seagrass beds, but they had a greater diversity index in the north and east than in the south. The abundance of gastropods, bivalves and polychaetes were significantly correlated with the biomass of H. pinifolia (65%, 39% and 27%, respectively); whereas only bivalves correlated significantly with the biomass of E. acoroides (36%). Treated wastewater effluents from shrimp farms did not affect the seagrass ecosystem. Water quality in the bay was suitable for natural resources preservation.
