With around one third of the world’s reef-building corals facing extinction (7), it is unsurprising that the blue rice coral is considered Vulnerable (1). One of the main risks to Montipora flabellata is an increased risk of mass coral bleaching episodes as a result of climate change (8). When sea temperatures rise over 27 degrees Celsius (3), corals become stressed and expel the zooxanthellae. For example, in 2002 and 2004 the north-western Hawaiian Islands suffered from bleaching episodes, resulting in almost 100 percent of Montipora flabellata colonies expelling their zooxanthellae (8). If the sea temperature rises are brief events coral may recover, but if they are prolonged coral tissue dies and only the white, limestone skeleton remains. Increased sea temperatures also affect corals by increasing their susceptibility to diseases and the numbers of diseases present (1). One study showed nearly 30 percent of reefs in Hawaii have Montipora-specific diseases, such as Montipora white syndrome which causes acute tissue loss (9).
Invasive species of algae have been reported in Hawaii and may cause problems by carpeting the coral, preventing light from reaching the zooxanthellae, thus inhibiting the algae’s ability to photosynthesise and produce energy. Sedimentation has a similar affect on the zooxanthellae (3), and also adversely affects dispersal of eggs and sperm during spawning, and hinders the settlement and development of the larvae (4). Sedimentation, caused by soil erosion following deforestation and intensive plantation agriculture (4), is no small problem; an estimated 1.9 million tons of soil enter the ocean each year from the island of Kaho’olawe alone (10).
Montipora flabellata may also be threatened by the crown of thorns starfish (Acanthaster planci), a voracious predator of reef-building corals in the Pacific. It has been observed preferentially preying on Montipora species although it prefers branching rather than encrusting corals so may have limited effect on Montipora flabellata (1).
Finally, Montipora flabellate, like many corals worldwide, is threatened by dynamite fishing, cyanide fishing (1), dredging for coastal construction (3) and pressures from tourism and recreation. Climate change can alter the native species dynamics, cause ocean acidification (1) and cause an increase in tropical storms and hurricanes. Volcanic eruptions may adversely affect Montipora flabellata if it reacts in a similar way to Montipora verrucosa which takes ten years to re-colonise a reef after a lava flow (11).