Coral Reefs of the Perhentian Islands: Abundance Levels and Distribution Patterns of Hosting Sea Anemones, and Implications for Citizen-Science Monitoring

Abstract

AbstractAround the Perhentian Islands, coral reefs have been undergoing significant degradation, as is reported annually through citizen-science coral reef monitoring programmes. Typical methodologies included in citizen-science surveys overlook the hosting sea anemones’ contribution to lowered live coral cover (LCC) on reef sites. As sea anemones compete with corals for suitable substrate, nutrients, and light availability, the current study was designed to investigate hosting sea anemone abundance and distribution patterns independently. In addition to identifying and assessing sites of localised sea anemone dominance, sea anemones were examined to identify factors that positively influence reproductive success and growth rate, including formations, hosting status, and resident Amphiprion species. In total, 379 sea anemone samples were analysed over 1600 m2 of Perhentian reef, making this study the first known independent investigation into sea anemone abundance patterns around the Perhentian Islands. Statistical analysis revealed that at site Village Reef, sea anemone abundance was higher than would be expected in healthy reef settings, and sea anemone cover was negatively impacting LCC. At second research site Teluk Keke, such analysis resulted in marginally insignificant results, potentially due to temporal onset differences or pressures exerted by other coral competitors. The most dominant sea anemone species, Heteractis magnifica (N=352), was analysed to test whether factors linked to higher reproductive success and growth rate were present in larger sea anemones. Results corroborate that larger sea anemones were significantly more likely to be actively hosting and were more often encountered in cluster formations. The current study employed a citizen-science method to explore its feasibility as a survey tool to identify reef sites undergoing dominance shifts, such as could be further developed and incorporated into currently used citizen-science monitoring programmes.