Population densities of a sea urchin Diadema setosum on shallow reef flats in the Gulf of Thailand
Keywords:Diadema setosum, sea urchin, shallow reef flats, Gulf of Thailand
The sea urchin Diadema setosum is a dominant invertebrate on coral communities in the Western Gulf of Thailand, as mechanical bioeroders that can have an influence on reefs; however, few works have examined its population densities on shallow reef flats. The population of the sea urchin D. setosum on reefs at the islands of Angthong, Chumphon, Phangan, Prachuap Khiri Khan, Samui, and Tao in the Western Gulf of Thailand was investigated during 2017 – 2018. The highest population density of D. setosum was found at the Chumphon archipelago and the lowest one was observed at the Phangan archipelago. We found a significant difference of sea urchin densities (p-value = 0.022), when comparing tourism and fisheries exploited areas, the last holding higher densities. This study showed that sea urchins can be found in high suspended sediment waters or fishing areas. For example, nutrients or organic that positively affected algae of sea urchin food, or factors affecting the amount of food in the area. Populations of D. setosum on shallow reef flats in the Gulf of Thailand can play a major role in coral ecosystems through. However, the data on the population ecology of several reef-associated sea urchins on shallow reef flats are very limited so these important to marine spatial planning in the future.
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