SEA URCHIN ECOLOGY 

Sea urchins are key benthic grazers on coral reefs, capable of shaping the community composition through herbivory, corallivory, and bioerosion. Due to these processes, sea urchins can influence both the carbonate budget and reef resilience, depending on their population density. Singapore harbours some of the most degraded yet resilient reefs in the region, but the ecology of the most dominant sea urchin—Diadema setosum—is not well understood. They exhibit a patchy distribution across Singapore’s Southern Islands, increasing in abundance with distance from the mainland, but the driver for this trend is unclear. They have been identified as an important bioeroder and macroalgae grazer on reefs where they are abundant, however, this finding was based on their daytime numbers, whereas D. setosum is nocturnal. The lack of knowledge concerning their diet on local reefs and variability of their bioerosion rate in response to environmental changes further restricts the appraisal of their ecological roles. In addition, how their populations are affected by the impacts of urbanisation are also not well understood. 

To gain a better understanding of D. setosum population ecology in Singapore, this project had the following objectives:

• Assess the factors influencing D. setosum local distribution patterns;

• Assess their population connectivity and genetic diversity;

• Characterise their local diet profile and assess the diet spatial variation;

• Quantify the pollutant load in their population; and

• Investigate their local bioerosion potential