Coral reefs are among the most biologically diverse and valuable ecosystems in the world. They support about 800 species of corals and more than 4000 species of fish and contribute immensely to coastal fisheries. About 25 percent of fish biodiversity in the world is found on coral reefs. Coral reefs are economically important because they support fisheries and tourism. They also protect the coast from sea erosion. Some species on coral reefs possess medicinally important compounds. For centuries, coral reefs have been a valuable resource in Sri Lanka, especially for the coastal communities.
Coral reefs are found throughout tropical oceans, growing best in shallow water environments. Reefs vary in form and size. The largest coral reefs in Sri Lanka are in the Gulf of Mannar while other well known reefs are found in the southern, eastern and northern coastal waters.
Corals can be divided into two broad categories – hard or stony corals and soft corals. Hard corals are the primary builders of coral reefs. Soft corals, which also include sea fans and sea whips, are found on coral reefs although they do not build reefs. The diameter of a corallite (skeleton of a coral organism) depends on the species and may vary from less than 1 mm to about 20cm. Two hundred and eight (208) species of hard corals have been recorded for Sri Lanka. The number of species of soft corals and sea fans is not known.
Download 2015 greeting cards: Reticulate Sea Fan, Mashroom Coral, Vase Coral, Carnation Coral, Honeycomb Coral, Flat-branched Sea Fan, Star Coral, Leather Coral, Brain Coral, Table Coral, Cup Coral, Staghorn Coral
Annella reticulata (Ellis & Solander, 1786)
Family name: Subergorgiidae
Annella reticulata is a large sea fan that grows to more than 2m in height and 1m in width. Branches consist of a horny material. The entire colony grows on a single plane with several branches growing out of the main axis. Numerous inter-connected sub-branches create the reticulate pattern that is characteristic of this species. Colour is highly variable; common colours are yellow, red, orange, cream and brown. This species is widespread in the Indo-Pacific region. In Sri Lanka, it occurs in relatively deep water, at a depth range between 20-50m in current-swept offshore reef habitats. It feeds on plankton swept in by the currents. Bacterial infections, blooms of filamentous algae and predators affect the health of Annella reticulata.
Fungia scutaria Lamarck, 1801
Family name: Fungiidae
The hard coral Fungia scutaria is among the twenty species of mushroom corals recorded for Sri Lanka. The coral is oval shaped and grows up to 15cm. The colour is usually brown; occasionally with green, pink, or yellow blotches on the upper surface. This species is widespread in the Indo-Pacific region and is common in the northwestern and eastern coastal waters of Sri Lanka at a depth range between 15-30m. It is uncommon in the northern, western and southern coastal waters. Fungia scutaria is rarely eaten by the crown-of-thorns starfish as they are mostly found in isolation from the main reef habitats.
Echinopora lamellosa (Esper, 1795)
Family name: Faviidae
The hard coral Echinopora lamellosa is one of two species of Echinopora recorded for Sri Lanka. Colonies are foliose and forms tiers of thin whorls or plates. Corallites are small; about 4mm in diameter. The colour is usually brown or grey with a pale margin. Echinopora lamellosa colonies can be more than 10m across and up to 1.5m high. This species is fragile and thrive best in calm shallow reef environments. It is widely distributed in the Indo-Pacific region and is a common species among shallow coral reefs of the Bar Reef, and offshore reefs in the Gulf of Mannar at Silavathurai and Arippu. Echinopora lamellosa is highly sensitive to environmental change and is vulnerable to the impacts of climate change. It is also a preferred food species of the crown-of-thorns starfish.
Dendronephthya Kükenthal, 1905
Family name: Nephtheidae
The number of species in the soft coral genus Dendronephthya in Sri Lanka is not known. Dendronephthya species depicted here is widespread in the Indo-Pacific region including Sri Lanka. Colonies are short and attached to the reef with a stalk. Fully expanded colonies are up to 30cm in height and branched with bushy bundles of polyps that form compact crowns as shown. Individual polyps are tiny, but visible to the naked eye and when extended give a fluffy appearance to each crown. The whole colony is capable of shrinking to a small size when not feeding. It is common on current-swept offshore reefs, at a depth range of 20-40m. Colour is variable; red, yellow, and purple are common colours. The stalk is usually white or paler than the brightly coloured crowns. This species is highly sensitive to environmental changes.
Diploastrea heliopora (Lamarck, 1816)
Family name: Faviidae
The hard coral genus Diploastrea has only one species. Diploastrea heliopora colonies are large and solidly built. They may be up to 2m high and 5m in diameter. Corallites are relatively large; up to 15mm in diameter, and neatly arranged giving a smooth appearance to the whole colony. Colour is uniform brown, green or grey. This species is widespread in the Indo-Pacific region. It is common in Sri Lanka, on the eastern and northwestern offshore reefs at a depth range of 10-30m. It is rare among northern and southern coastal reefs. Diploastrea heliopora is highly resistant to predation and is rarely eaten by the coral predator, the crown-of-thorns starfish.
Subergorgia Gray, 1857
Family name: Subergorgiidae
Several species of sea fans belong to the genus Subergorgia. The total number of species that occur in Sri Lanka is not known. Subergorgia shown here grows to about 20cm in height. Branches consist of a horny material. The colony grows on a single plane and branches divide and grow laterally. Branches do not join and form a net-like structure. A groove running along the length of each branch on the opposite face to the growth plane is characteristic of this group. Common colours are brown, red and grey with white polyps. Subergorgia is widespread in the Indo-Pacific region. In Sri Lanka, it occurs in relatively deep water, at a depth range between 15-50m in current-swept offshore reef habitats. Feeds on plankton swept in by the currents. Bacterial infections affect the health of Subergorgia.
Favites halicora (Ehrenberg, 1834)
Family name: Faviidae
The hard coral Favites halicora is among the seven species of Favites recorded for Sri Lanka. Colonies are dome shaped or encrusting with a smooth or hillocky surface. Corallites are about 10mm in diameter and are arranged in a honey-comb like pattern with raised ridges between them. It has a dense strong structure and is capable of withstanding waves. Favites halicora is usually brown or green. It is widespread in the Indo-Pacific region and a common reef building coral in Sri Lanka. This species can be seen among fringing reefs around the country and on some offshore reefs to a depth of about 12m. Favites halicora is highly sensitive to temperature change, and is vulnerable to the impacts of climate change. The crown-of-thorns starfish rarely eat this species.
Sarcophyton Lesson, 1834
Family name: Alcyoniidae
The number of species of soft corals in Sri Lanka in the genus Sarcophyton is not known. This species forms large colonies up to 1.5m in diameter. A large stalk at the base anchors the whole colony to the reef. Individual polyps are tiny, and when extended, give a fluffy appearance to the whole colony. Common colours are brown, grey and green. The Sarcophyton species shown here is one of the most common soft corals in the Indo-Pacific region including Sri Lanka. Sarcophyton is common on fringing and offshore reefs to a depth of about 30m, but is abundant in the east and the north when compared to other areas of the country. This species is highly sensitive to changes in sea surface temperature and vulnerable to impacts of climate change. The egg cowry shell (Ovula ovum) is a predator of this species.
Platygyra daedalea (Ellis and Solander, 1786)
Family name: Faviidae
The hard coral Platygyra daedalea is among the five species of Platygyra recorded for Sri Lanka. Platygyra daedalea forms large colonies up to 2m across and is a common species in shallow reef habitats to a depth of about 15m. They are dome shaped or encrusting. The surface has meandering valleys and ridges. Each valley contains many individual coral polyps that are connected through the living tissue of the colony. The colour of Platygyra daedalea is variable. Usually, colonies have brown ridges and green valleys. This species is widely distributed in the Indo-Pacific region and common on all reef habitats around Sri Lanka. Colonies in shallow water are vulnerable to the impacts of climate change. It is also vulnerable to predation by the crown-of-thorns starfish.
Acropora hyacinthus (Dana, 1846)
Family name: Acroporidae
The hard coral Acropora hyacinthus is among the 33 species of Acropora recorded for Sri Lanka. Colonies are tabulate and round with a diameter up to 1.5m. They are arranged in tiers and form extensive patches over 5m across and up to 1.5m in height. Branches are small, thin and fragile. Colonies are brown with a pale brown or white margin. This species is found up to a depth of about 15m. Colonies in areas exposed to wave action has fused branches whilst those in relatively calm water have longer branches. Acropora hyacinthus is widespread in the Indo-Pacific region and a common species in Sri Lanka. It is highly sensitive to changes in temperature and is vulnerable to the impacts of climate change. This is a preferred food species of the crown-of-thorns starfish.
Tubastraea Lesson, 1829
Family name: Dendrophylliidae
The hard coral genus Tubastraea belongs to non-reef building corals, but occurs on reef habitats. This species does not form large colonies and thus does not contribute to the formation of reefs. Colonies rarely exceed 15cm in diameter. The corallites are relatively large with a diameter of about 10mm. It is common under ledges and on rock surfaces at a depth range of 20m-60m. Orange, yellow, and pink are common colours of Tubastraea. This species feeds on planktonic organisms, which it captures with relatively large tentacles as shown. Tubastraea is widely distributed throughout the Indo-Pacific and is abundant on rock boulders and shipwrecks in Sri Lanka. Many predators avoid this species due to large polyps and stinging tentacles.
Acropora formosa (Dana, 1846)
Family name: Acroporidae
The hard coral Acropora formosa is among the 33 species of Acropora recorded for Sri Lanka. It is a branching coral that forms extensive patches over 10m across among shallow reefs to a depth of about 8m. Thickets are about 1.5m high and formed by intertwined branches. Branch length depends on environmental conditions. Shallow water colonies have short branches whilst deep water colonies have long branches. Colonies are various shades of brown with white or purple branch ends. Acropora formosa is one of the most widespread reef-building corals in the Indo-Pacific region and is abundant on shallow coral reefs all around Sri Lanka. It is highly sensitive to changes in temperature and is vulnerable to the impacts of climate change. It is one of the preferred food species of the crown-of-thorns starfish.
Not all hard corals build reefs. Reef building corals contain photosynthetic microalgae within their tissues, which provide most of the energy requirements of the coral and are sensitive to temperature and salinity of the seawater. When stressed, microalgae are destroyed and the corals lose their source of food and colour. This condition is known as coral bleaching. A large scale coral bleaching event in the Indian Ocean in 1998, caused by global warming destroyed many coral reefs including reefs in Sri Lanka.
Today coral reefs are being lost at an alarming rate due to climate change and human activities such as destructive fishing, over-harvesting of resources, coastal development and pollution. Coral reefs are also damaged by predators such as the crown-of-thorns starfish.
Corals are protected in Sri Lanka under the Fauna and Flora Protection Act. Four marine protected areas have been established to conserve coral reefs. The Hikkaduwa Marine Sanctuary established in 1979 was the first and the largest is the Bar Reef Marine Sanctuary with an area of 306 km2.
Sri Lanka Telecom is committed to “preserving heritage for tomorrow”, for the benefit of the future generations to ensure long term sustainability of the country’s rich natural and cultural heritage. The SLT 2015 calendar is produced under the sub-theme “Corals of Sri Lanka” and aims to raise awareness among the general public about the importance of preserving ecosystems for future generations.
Resource Institute: IUCN (International Union for Conservation of Nature and Natural Resources), country office in Sri Lanka.
All Text & Introduction Page Photograph by Arjan Rajasuriya, Coordinator of Marine & Coastal Thematic Area at IUCN.
Photographs by: Arjan Rajasuriya - IUCN, Naren Gunasekara and Nishan Perera.
Graphic designer: H.K.S. Sathyajith.