Acropora longicyathus

Acropora longicyathus is a stony coral in the family Acroporidae, recognized by its branching, corymbose to arborescent colonies with tubular, tapering branchlets radiating from a central axis. Like other Acropora species, it is a colonial cnidarian composed of many small polyps that secrete calcium carbonate skeletons, building the physical framework of reef ecosystems. It relies on symbiotic zooxanthellae algae for much of its energy, supplementing this through polyp feeding on plankton at night.

As a reef-building species, it provides habitat structure and shelter for a wide range of reef-associated fish and invertebrates.

The species occurs across the Indo-Pacific, with records from Australia, Japan, China, Palau, Micronesia, and the Marshall Islands. It inhabits marine neritic and coastal/supratidal zones, typically on reef slopes and lagoons in shallow, clear waters.

Population declines stem from multiple compounding pressures. Coastal development and agricultural runoff introduce sediment, nutrients, and pollutants that degrade water quality, while domestic wastewater discharge exacerbates eutrophication. Fishing and harvesting activities, along with recreational use, cause physical damage to fragile branching colonies.

Outbreaks of coral predators such as crown-of-thorns starfish, along with coral diseases, add further mortality. Ongoing habitat alteration and shifting environmental conditions, including bleaching events linked to elevated sea temperatures, continue to reduce colony survival and reproductive success.

Conservation efforts include the species' listing on CITES Appendix II, inclusion in marine protected areas across parts of its range, and reef monitoring programs tracking bleaching and disease incidence. Restoration projects using coral fragmentation and outplanting have been trialed in some Acropora species regionally.

Population trends are decreasing, and the species is assessed as Endangered, reflecting sustained habitat degradation and slow recovery potential given ongoing cumulative threats.