Community Structure and Environmental Drivers of Benthic Mollusks in the Seagrass Ecosystem of Kupang Bay, Indonesia

Kupang Bay in Indonesia has a multispecies seagrass ecosystem that plays a vital role in the coastal ecosystem, including serving as a primary habitat for benthic mollusks. Increasing anthropogenic pressure and environmental changes along the Kupang coast continue to degrade the quality of this ecosystem, making an assessment of its health status critically important. Given that benthic mollusks are highly vulnerable to environmental changes, the relationship between the structure of the benthic mollusk community and the seagrass ecosystem can serve as an effective bioindicator for assessing the health of the seagrass ecosystem in Kupang Bay. Therefore, this study aims to determine the community structure of benthic mollusks associated with seagrass ecosystems and to identify the environmental factors influencing their presence at six stations in Kupang Bay. Seagrass and mollusk sampling was conducted using the quadrant line transect method, and the relationship between environmental factors and mollusk presence was analyzed using Redundancy Analysis. Seven seagrass species were recorded, with the highest density found at Sulamu (994.13 shoots/m²) and the lowest at Cafe Tebing (272.61 shoots/m²). A total of 397 benthic mollusk individuals belonging to 28 species, 26 genera, and 18 families were successfully identified, consisting of 20 species of Gastropoda totaling 362 individuals and 8 species of Bivalvia totaling 35 individuals, with Clypeomorus batillariaeformis being the most abundant species. Tablolong Beach recorded the highest mollusk abundance with a total of 165 individuals but the lowest diversity, whereas Lalendo showed the opposite pattern, with the highest diversity (H' = 1.88) despite lower abundance. RDA results indicate that seagrass density, dissolved oxygen, and sediment organic matter content collectively explain 75.1% of the variation in benthic mollusk distribution, distinguishing three habitat preference groups: stations with high organic matter content are preferred by Cypraeidae and Arcidae; stations with high dissolved oxygen are preferred by Pinnidae, Mytilidae, and Strombidae; and stations with high seagrass density are preferred by Cerithiidae.