The Dongsha Atoll National Park has the largest seagrass bed in Taiwan. This lush expanse of undersea green carpet is also the home of the Smaragdia rangiana, commonly known as the Emerald nerite. It is a species of sea snail with a white striped green shell, similar to an emerald jewel, and also acts as a natural camouflage. The blades of the seagrasses not only provide a habitat and sanctuary, they are also the source of foods for these snails.

In earlier times, Emerald nerites could be found in Green Island, estuaries of Pingtung, and intertidal zones of the Western coasts. However, their populations have been dwindling from the destruction of their habitats by coastal developments. The discovery of this specie in Dongsha not only signifies the rich biodiversity of the Dongsha Atoll National Park, but also acts as a genetic preserve for this specie in Taiwan. The seagrass in the Dongsha aquatic regions acts as primary producer, stabilizes the sandy sea bottoms, and provides nursing sanctuaries for many marine organisms. The seagrass bed in the Dongsha National Park is the largest in Taiwan with an estimated area of 1,185 acres. The protected seagrass bed not only acts as a perfect habitat for the Emerald nerites, it is also safe haven for many other organisms.

At only 0.5cm, the tiny Emerald nerite has beautiful emerald-green coloration. Its white striped green shell acts as a perfect camouflage in the seagrass. In addition, the multi-dimensional layout of the seagrass performs both as its habitat and as a rich source of nutrients. According to Assistant Professor Yuh-Wen Chiu of the Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, who has conducted biomes investigations at Dongsha Island, the Emerald nerite is dioecious (sexually distinctive individuals) like all other nerite species. The female nerites will produce translucent eggs on the blades of the seagrass. The hatched larvae will drift with the currents and attach to other seagrasses to continue their life cycles.

The vast expanse of the seagrass bed at Dongsha Island is not only the largest in Taiwan, its species diversity is also unique among the islands of the Southern Sea, providing not only habitats for mollusks like the Emerald nerites but also other types of fish and marine invertebrates. The seagrass bed is truly a precious specimen for marine biological education.

Emerald nerite – Green Jewel in seagrass / Photo by Hsiu-Min Wang Translucent and gelatinous round masses – eggs of Emerald nertie / Photo by Hsiu-Min Wang