Turbinaria Coral

Like many coral species, Turbinaria bifrons is zooxanthellate, which means that its tissues contain large numbers of single-celled algae called zooxanthellae. The coral and the algae have a symbiotic relationship, in which the algae gain a stable environment within the coral's tissues, while the coral receives nutrients produced by the algae through photosynthesis. By harnessing the sun's energy in this way, corals are able to grow rapidly and form vast reef structures, but are constrained to live near the water surface (3). While, on average, zooxanthellate coral can obtain around 70 percent of its nutrient requirements from zooxanthellae photosynthesis, the coral may also feed on zooplankton (4). The polyps' tentacles, which in this species are mostly extended at night, contain stinging cells called “nematocysts” that trap the drifting zooplankton , directing it into the central mouth, which also acts as an anus to excrete waste products after digestion (3) (4). Neighbouring polyps within a Turbinaria bifrons colony are linked by small tubes that distribute water and nutrients evenly, creating a similar rate of growth, and preventing competition for space (3). Turbinaria bifrons is capable of both asexual reproduction, whereby the polyps proliferate through the production of clones, and by sexual reproduction, in which the polyps spawn large numbers of sperm and eggs. The fertilised eggs develop into planktonic larvae, which travel through the water column, before settling and metamorphosing into a sessile polyp (3) (5).

Like all coral species, Turbinaria bifrons is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which means that all international trade is strictly controlled by the use of permits and annual quotas (2). In addition, Turbinaria bifrons falls within several Marine Protected Areas across its range (1). Specific conservation measures recommended for this species include carrying out extensive studies of its population, biology, and ecology, along with more research into existing and potential threats. In response to the threat of climate change, artificial propagation and preservation of sperm and eggs may become necessary to safeguard Turbinaria bifrons against complete extinction (1).

Like other colony-forming corals, Turbinaria bifrons colonies are composed of numerous small polyps, which are soft-bodied animals, related to anemones. Each polyp bears numerous tentacles that direct food into a central mouth, where it is digested in a sac-like body cavity. One of the most remarkable and ecologically important features of corals is that the polyps secrete a hard skeleton, called a “corallite”, which over successive generations contributes to the formation of a coral reef. The coral skeleton forms the bulk of the colony, with the living polyp tissue comprising a thin, often colourful, veneer. In Turbinaria bifrons, colonies initially form flat, solid plates, but as the coral develops, many sheet-like, wavy fronds grow upwards from this foundation. The polyps, which are found on both sides of these fronds, form small conical projections, which may be coloured grey, green or brown (3).

Turbinaria bifrons occurs in shallow reefs in tropical waters between depths of 2 and 25 metres, as well as in rocky areas within the intertidal zone in subtropical locations (1) (3).

Turbinaria bifrons is found in the Indo-West Pacific, from southern Japan, through the South China Sea and Indonesia, south to tropical Australia (1).

Classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix II of CITES (2).

Around one third of the world's reef-building corals are threatened with extinction (6). The principal threat to corals is the rise in sea temperature associated with global climate change. This leads to coral bleaching, where the symbiotic algae are expelled, leaving the corals weak and vulnerable to an increasing variety of harmful diseases. Turbinaria bifrons is thought to be particularly susceptible to bleaching, and estimates indicate that it has suffered a global decline of around 38 percent over the last 30 years (1). Other harmful effects of climate change include more frequent destructive, extreme weather incidents, as well as increased ocean acidification, which impairs a coral's ability to form a skeleton. These global threats are compounded by localised threats from pollution, destructive fishing practices, invasive species and human development (1) (6).

Turbinaria bifrons, commonly known as disc coral, is a species of colonial stony coral in the family Dendrophylliidae. It is native to the Indo-Pacific region. It is a zooxanthellate coral that houses symbiont dinoflagellates in its tissues. This is an uncommon species and the International Union for Conservation of Nature has rated its conservation status as being "vulnerable".

zooxanthellate

Central Indo-Pacific to Japan