Coral Reefs of India

Definition and introduction

Coral reefs are one of the most ancient and dynamic ecosystems of India. Coral reefs not only provide a sanctuary to a myriad of marine life but also play a key role in protecting the coastline from erosion. In addition, people living along the 8,000 km long coastal stretch of India depend on coral reefs for their livelihood (Venkataraman and Alfred, 1998, Venkataraman, 2003). India is centrally placed within the warm tropical region of the Indian Ocean and exhibits extensive coral reefs in its marine territories. In India, major coral reef ecosystems are seen in Gulf of Mannar, Gulf of Kachchh, Andaman & Nicobar, and Lakshadweep Islands, which embrace all the three major reef types (atoll, fringing, and barrier) and include diverse and extensive reef areas of the Indian Ocean (Figure 1). Fringing reefs are found in the Gulf of Mannar and Palk Bay. Platform reefs are present along the Gulf of Kachchh. Patch reefs are present near Ratnagiri, Malvan, and Kerala coasts. Fringing and barrier reefs are found in Andaman and Nicobar Islands. Atoll reefs are found in Lakshadweep. Absence of reefs in the Bay of Bengal along the northeast coast is attributed to the immense quantity of freshwater and silt brought by the rivers such as Ganga, Krishna, and Godavari. The total area of coral reefs in India is estimated to be 2,375 sq km.

Coral Reefs of India. Figure 1

Major coral reef areas in India.

The studies on the taxonomy of Indian coral reef started as early as 1847 by Rink in Nicobar Islands, and later in 1898, Thurston worked on coral reefs in Gulf of Mannar region. During the whole of twentieth century, many foreigners contributed to coral reef studies in India. Pillai (1983, 1986), the first Indian worker, published many papers on the coral diversity from all the four major coral reefs of India followed by Venkataraman (2003, 2006), Venkataraman and Alfred (1998), and Venkataraman et al. (2003).

Coral reefs: East Coast of India

Gulf of Mannar

The Gulf of Mannar reefs are found around a chain of 21 islands that lie along the 140 km stretch between Tuticorin and Rameswaram. These islands are located between latitude 8° 47’N and 9° 15’N and longitude 78° 12’E and 79° 14’E. The islands lie at an average distance of 8 km from the main-land. They are part of the Mannar Barrier reef, which is 140 km long and 25 km wide between Pamban and Tuticorin. Different types of reef forms such as shore, platform, patch, and fringing type are observed in the Gulf of Mannar (Venkataraman et al., 2003). The islands have fringing coral reefs and patch reefs around them. Narrow fringing reefs are located mostly at a distance of 50–100 m from the islands. On the other hand, patch reefs rise from depths of 2–9 m and extend to 1–2 km in length with width of as much as 50 m. Reef flat is extensive in almost all the reefs in the Gulf of Mannar. Reef vegetation is richly distributed on these reefs. Reef flat and reef vegetation including algae occupies 65 and 14 sq km, respectively (D.O.D and S.A.C., 1997). Pillai (1986) had provided a comprehensive account of the coral fauna of this region. There are about 94 species of corals belonging to 32 genera in the Gulf of Mannar. The most commonly occurring genera of corals are Acropora, Montipora, and Porites. Extensive sea grass beds are present; green turtles, olive ridley turtles, and dugongs are dependent on these sea grasses as their feeding ground.

Andaman and Nicobar Islands

The Andaman and Nicobar group of Islands is located in the South East of the Bay of Bengal, between 6°–14°N latitude and 91°–94°E longitude. They are the emerged part of a plate edge mountain chain and lie on a ridge that extends southward from the Irrawaddy delta area of Burma, continuing the trend of the Arakan Yoma range.

The Andaman and Nicobar group of islands consist of 530 islands, of which only 38 are inhabited, along with a number of exposed islets and rocks. The principal of these is the North Andaman, Middle Andaman with Ritchies archipelago in the east, South Andaman, little Andaman, Baratang, and Rutland Island. The coral reefs are of fringing type and except for a few investigation reports, the reefs of the area still largely remain unknown. A deep oceanic ridge along 10°N separates the Andaman Group and the Nicobar group of islands. The orientation of the chain of islands is north-south. In these island groups, there are two Marine National Parks viz., Mahatma Gandhi and Rani Jhansi Marine National Parks. The coral fauna is diverse when compared to other parts of India (Turner et al., 2001).

West Coast of India

The West Coast of India between Mumbai and Goa is reported to have submerged banks with isolated coral formations (Nair and Qasim, 1978). Coral patches have been recorded in the intertidal regions of Ratnagiri, Malvan and Rede, south of Mumbai (Qasim and Wafer, 1979), and the Gaveshani bank, 100 km west to Mangalore (Nair and Qasim, 1978).

Malvan

The Malvan coast forms part of the Western Ghats where the Sahyadri ranges gradually meet the Arabian Sea. From Vengurla point, the coast tends towards the north for about 22 km. From Malvan bay, a chain of submerged and exposed rocky islands extends directly south to 15°53’N and 73°27’E. In this chain, several islands exist including Vengurla Rocks at the Southern tip and Sindhudurg Fort at the northern tip. Other small islets around Sindhudurg Fort are Mandel Rock, Malvan Rock, etc. Most of the marine flora and fauna in the intertidal area are exposed during low tide. However, during lowest low tides (particularly negative tides), the coral reefs get exposed. Porites, Coscinaraea, Turbinaria, Favia, and Pseudosiderastrea are some of the genera reported from this coast (Venkataraman et al., 2003). Siltation is high and salinity may drop to 20 ppt during the monsoons in some habitats, which may restrict the growth of ecologically sensitive forms of ramose corals.

Lakshadweep Islands

The Lakshadweep Islands lie scattered in the Arabian Sea at about 225 – 450 km from the Kerala coast. Geographically, the islands lie between 8°N–12°3’N latitude and 71°E – 74°E longitude. The islands consist of coral formations built up on the Laccadive-Chagos submarine ridge rising steeply from a depth of about 1,500 to 4,000 m off the west coast of India. The Union Territory of Lakshadweep along with the Maldives and the Chagos Archipelagoes form an interrupted chain of coral atolls and reefs on a continuous submarine bank covering a distance of over 2,000 km. This ridge is supposed to be a continuation of the Aravali Mountain, and the islands are believed to be remnants of the submerged mountain cliffs. There are six tiny islands, 12 atolls, 3 reefs and 5 submerged banks, covering an area of 32 km² with lagoons occupying about 4,200 km². Only 11 of the 36 islands are inhabited. Minicoy Island is separated from the rest of the islands by a 180 km wide stretch of sea known as the Nine-degree Channel.

The coral fauna of Lakshadweep is known to harbor 105 species belonging to 37 genera (Pillai, 1996). Acropora spp., Pocillopora spp., Porites spp., and massive and encrusting favids dominate the lagoon and reef flat faunal elements. Psammocora spp. are common in the northern islands. There is an abundance of blue coral Heliopora coerulea. Millepora spp. is dominant in the lagoon. Minicoy has species such as Lobophyllia and Diploastrea that are common to the Maldives but rarely found in the northern islands. Similarly, the genera Montipora and Echinopora recorded from the northern group of atolls are not recorded in Minicoy.

Gulf of Kachchh

Gujarat State has a 600 km long coastline, which is very rich in various edible fishes and various types of algae. The Gulf of Kachchh is the richest source of floral, faunal and marine wealth of India, as it provides favorable conditions for breeding and shelter to all marine life in the 42 islands. The corals in the Gulf of Kachchh survive through extreme environmental conditions such as high temperature, salinity changes, and high-suspended particulate loads. Gulf of Kachchh Marine National Park and Sanctuary is the first National Park in the country (457.92 sq km). The Gulf of Kachchh has the best developed coral reefs along the western coast. Out of the 42 islands in the Gulf, 34 islands are surrounded by fringing or platform reefs. Out of 37 hard coral species reported earlier, only 36 are currently found.

Geology and geomorphology of Indian coral reefs

Coral reefs characterize an ecosystem of high biological diversity, having the greatest number of species of any marine ecosystem. Coral reefs act as a barrier against wave action along coastal areas thus preventing coastal erosion as well as protecting mangroves and seagrass beds in certain areas, which are the breeding and nursing grounds of various economically important fauna (Venkataraman and Alfred, 1998). However, the processes of erosion, sedimentation, periodic storms, flooding, and sea level change, continually modify the ecosystem. The Holocene transgression, the latest episode of sea-level fluctuations, has left behind many signatures which provide insight into the nature of these changes. Direct and indirect palaeo sea-level indicators (see: Sea Level Indicators ) have been identified with transgressive, regressive or still-stand conditions. These include specific biological indices of corals, molluscs, foraminifers, etc., and certain geomorphological features such as submarine terraces, reefs, notches, raised marine deposits, beach rocks, buried channels, etc (Vora et al., 1996). Glacio-eustatic sea-level fluctuations, along with relief, lithology, sedimentation, tectonic movements, etc., produce depositional and erosional patterns which govern the topography of the continental shelf of the Andaman and Nicobar Islands and other coral reef areas of India (Bruckner, 1988). The topography of the continental shelves where major coral reefs of India are found (Gulf of Kachchh, Gulf of Mannar, Lakshadweep, and Andaman and Nicobar Islands) is mainly governed by depositional and erosional processes, which occur during glacio-eustatic sea level fluctuations. Other factors involved, directly or indirectly, are structure, lithology, sedimentation, tectonic movements, and climatic changes.

Seismic data from the west coast of India revealed the occurrence of buried reefs off Saurashtra and Ratnagiri, indicating pinnacles and protuberances of different heights. The cliffy coast of southern Saurashtra has preserved a record of the sea level changes during the late Quaternary (Rao and Wagle, 1997). Based on the geomorphic positions of the notches, the older sea strand lies at an elevation ranging from 12 to 15 m above the present BMSL and has been attributed to the last interglacial (MIS-5). Following this, a major tectonic uplift of about 6–9 m was experienced by the southern cliffed coast. The Holocene sea level was recorded at 4–5 m which is about 2 m higher than the general MIS-1 sea level. Thus, the submarine terraces on the shelf must have also been formed during the late Pleistocene to mid-Holocene still stands of the sea level. Radiocarbon dates of surficial samples of algal, oolitic, and coralline limestone (Nair and Hashimi, 1980) collected from the terraces and/or in their vicinity suggest that the innermost terrace along the shelf (55–60 m) is ca 7,845 yrs B.P., and the outermost terrace on the shelf is ca 11,150 yrs B.P.

The distribution of reefs on the west coast shelf is random which perhaps may imply that conditions for reef growth have not been uniform. It is interesting to note that between Mumbai and Mormugao, where the shelf is relatively broader, reefs occur abundantly on the middle and outer shelf. On the other hand, south of Mormugao, where the shelf is narrow, they are sparsely present and only on the outer shelf. Submerged coral reefs may be defined as reefs that were established in relation to a pre-existing sea-level lower than present and occur at depths greater than that commonly associated with vigorous growth of reef building, hermatypic corals. Further, the radiocarbon dating of coral and associated fauna indicates that they are of early Holocene age.

The Lakshadweep Islands rise from a submarine platform with coral reefs in the form of an atoll. It is crescent-shaped having a north-south orientation. The western margin of the lagoon is a submarine bank with a narrow reef below. The lithology is composed of an upper 1–2 m-thick layer of coral rubble, below which is a compact porous crust of conglomerate and soil composed mostly of coral sand. Topography is a flat 1–2 m above sea level. Erosion occurs mostly along the shore towards the northeast and northwest (Anon, 1990).

The Gulf of Mannar extends from Tuticorin to Rameswaram Island in a SW-NE direction and lies between 78°5’ & 79°30’E longitudes and 8°47’ & 9°15’N latitudes, a distance of about 140 km. There are 21 islands between Tuticorin and Rameswaram. All islands are composed of a calcareous framework of dead reef and sand and have a low and narrow sandy coast. Around all offshore islands, well-developed coral reefs occur. Geomorphologically, coral reefs in this area are of fringing type, though some patchy corals are also observed in between Appa Island and Pilliyarmuni Island, and in some areas such as the Bharathinagar coast and the southeast coast of Kariya Shuli Island (Loveson, 1993). Wave cut platforms are common on the coast of Mandapam, Ramaswami Madam, Pudumatam, Valinokkam, etc. Along the coast of the Gulf of Mannar, cliffs occur though at some places these features have been destroyed due to slumping. In the Gulf of Mannar, the slope and width of the continental shelf is approximately the same as the average for the eastern coast of India (Ahmed, 1972). The total width of the shelf is around 30 km having a slope of about 21’. The slope near the shore is about 4’. Recent depth contour maps indicate that the seafloor level decreases along the coast and around the islands due to emergence of the land or lowering of sea level (due to tectonism) and sediment deposition. The beach is gently sloping and marked with altered crests and troughs that are formed due to wave action. As the Gulf of Mannar is on the lee side of the northeast monsoon, there is no long-shore drift from the northeast that might affect the morphology of the spit, (Ahmed, 1972). The southwestern shore of Rameswaram has a tongue shaped spit.

The Andaman and Nicobar Islands are parallel to the arcuate plate boundary separating the Indian and Sunda Plates east of the 9°E ridge (Dasgupta and Mukhopadhyaya, 1993; Rajendran and Gupta, 1989). The ridge is believed to have been formed from sediments scraped off the descending Indian Plate interleaved with ophiolites from the ocean floor beneath the Bengal Fan. In that, the islands are bounded to the east by strike-slip faults and spreading centers, and to the west by a subduction zone, the Andaman and Nicobar ridge acts as a small tectonic plate that has been referred to as the Burma Plate by Curray et al. (1982) and as the Andaman Plate by Dasgupta (1993). The geology of the Andamans is described by Oldham (1884) and Tipper (1911).

A series of earthquakes ranging up to a magnitude of 7.5 under the Andaman and Nicobar Islands on 26 December 2004 shook the entire Andaman Sea region. The end result was that the Burma Plate, which contains the Islands, tilted during an earthquake “swarm” lasting for about 8 min after the major quake off Sumatra. Thus, these islands were a source of the tsunamis that spread out across the Indian Ocean and themselves impacted by tsunamis from the whole series of plate movements on that morning. The effects were very different on the mainland of India to the offshore Andaman and Nicobar Islands.

The primary slip offshore of Sumatra was followed by two other slips towards the north. Though some of these findings need to be further substantiated, the fact remains that the Sumatra earthquake caused significant changes to the earth’s tectonic processes (Ortiz and Bilham, 2003). The Andaman and Nicobar area, including Car Nicobar, Katchel, and Campbell Islands were not only affected by the earthquake but also by the tsunami surge. A subsidence of 1–2 m affected the Nicobar Islands with the maximum down-throw at Indira Point near Great Nicobar. Out of the total area of the Nancowry group of islands, 15.64% of the area has undergone major changes. Nearly 6.8% of the area is submerged and 8.9% of area damaged. Maximum change (more than 42%) has been observed in Trinket Island. More than 23% of Katchall and 9% of Camorta and Nancowri and Tarasa groups have undergone major changes. This resulted in a rise in sea-level, inundating the coastal settlements and narrowing the beaches of the islands. Measurements made at Aerial Bay (Diglipur) and Rangat revealed retreat of sea level to the extent of 1.3 m at Campbell Bay, 1.0 m at Chattam Island, 0.8–1.0 m in Aerial Bay and 0.4–0.6 m at Rangat. Land surveys at Diglipur and Mayabunder jetties (North Andaman) confirm a vertical uplift of the land up to 1.2 m from the pre-earthquake levels; exposed piles of the jetties, coral reefs and the receded waterline at these jetties stand as testimony to this change (Figure 3).

Coral Reefs of India. Figure 3

The exposed coral reef in the Landfall Island, North Andaman.

The coral reefs of Andaman and Nicobar Islands have been damaged by the impact of the recent tsunami and physical removal of other coral reef associated flora and fauna. The tsunami waves increased the sediment load which has smothered and killed sediment sensitive corals and sea grasses. There is significant contamination of coral reefs and coastal waters by run-off from the land, with large quantities of waste and pollutants, debris, soil, and organic matter. Nesting beaches for the five species of globally threatened marine turtles in the Andaman and Nicobar Islands and on the east coast of India have also been damaged.

Coral reef associated biodiversity

Scleractinian corals

Pillai (1983) recorded a total of 199 species divided among 37 genera, from India, which includes Lakshadweep (78 species), the Gulf of Kachchh (37 species), Palk Bay and the Gulf of Mannar (94 species) and Andaman and Nicobar Islands (135 species) (Figure 2). This account includes both hermatypic and ahermatypic corals from the four major coral reefs of India. Venkataraman et al. (2003) identified 15 families, 60 genera and 208 species of Scleractinia (reef building and hermatypic corals) from the four major reefal areas of India such as Gulf of Kachchh (36 species), Lakshadweep (91 species), Gulf of Mannar and Palk Bay (82 species), and Andaman and Nicobar Islands (177 species).

Coral Reefs of India. Figure 2

Diversity Scleractinia in the major coral reef areas in India.

The diversity of scleractinian corals in Gulf of Kachchh is very poor when compared to all the other three major regions of India. Families such as Asterocoeniidae, Pocilloporidae, Euphyllidae, Oculinidae, Agariciidae, Fungiidae, and Trachyphylliidae are totally absent. Species such as Siderastrea savignayana and Acanthastrea hillae are reported only from Gulf of Kachchh. Twelve families, 34 genera and 91 species are reported from the Lakshadweep Islands. Families such as Astrocoeniidae, Pectiniidae, and Trachyphylliidae are absent. Among the 60 genera recorded in India, only 34 are reported so far from Lakshadweep. Thirteen families, 27 genera and 82 species are reported from the Gulf of Mannar and Palk Bay. From the Andaman and Nicobar Islands, 15 families, 57 genera, 177 species are reported. All the fifteen families reported from India are represented in these islands.

Algae

Marine algae or seaweeds form an important reef resource in India. A recent publication on the compilation of all the new records of marine algae of India shows that benthic marine algal flora of Indian coasts comprises 844 species under 217 genera including forms and varieties (Oza and Zaidi, 2000). Out of these, the maximum number have been recorded from the Gulf of Mannar (302), followed by 202 species from the Gulf of Kachchh, 159 species from the Malvan coast, 89 species from the Lakshadweep group of Islands and 82 from Goa. In India, seaweeds are exploited and used as raw materials for the production of agar, alginates and seaweed liquid fertilizer. Data on seaweed landings in Tamil Nadu from 1978 to 2000 reveal that the quantity (dry wt) extracted in a year during this period varied from 102 to 541 t for Gelidiella acerosa, 108–982 t for Gracilaria edulis, 2–96 t from G. crassa, 3–110 t for G. foliifera, and 129–830 t for G. verrucosa (Ramalingam, 2000).

Sea grass

Indian coral reefs embrace only 6 genera and 14 species of sea grasses. Distribution of sea grasses along the Indian coast varies with varying species diversity viz. Gulf of Mannar 13 species, Gulf of Kachchh and Lakshadweep 7 species and Andaman and Nicobar reefs 9 species (Kannan et al., 1999). All the 6 genera of sea grasses with 11 species are recorded from the Palk bay region. Of the 11 species, C. serrulata, H. ovalis ovalis, K. pinifolia, and S. isoetifolium are the most widely distributed. Out of the 14 species of sea grasses, nine species occur in the Andaman and Nicobar Islands.

Other marine fauna

Other marine fauna illustrate the great diversity of India’s coral reef biota. Some 451 species of sponges from 169 genera have been recorded (Pattanayak and Buddhadeb, 2001). Dominated by Desmospongia, greatest diversity is found in the Gulf of Mannar and Palk Bay. Four turtle species (leather back, Hawksbill, green and Olive ridley) have been observed nesting in the Andaman and Nicobar Islands, (Basker, 1984). Dolphins are common in many areas and dugong in areas of sea grass. More than 1,000 coral reef fish species are found with greatest diversity in the Andaman and Nicobar Islands. There are 3,570 species of marine molluscs (Subba Rao, 1998), almost 3,000 species of Crustacea (Venkataraman and Krishnamoorthy, 1998) and 765 species of echinoderms, 257 in the Andaman and Nicobar Islands alone (James, 1987).

Threats to coral reefs

Coral reef resources have traditionally been a major source of food for local inhabitants and of major economic value in terms of commercial exploitation. The human exploitation of marine resources has increased dramatically over the last few decades for both reasons of commercial and subsistence living. Coral reef ecosystems of India have been exploited for a very long time, but it is only in the last century that the rate of exploitation has increased dramatically due to the increase in the human population. Except for some of the Andaman-Nicobar Islands, no pristine area exists today.

Varied human activities which are a cause for concern over and above the natural disturbances include, runoff and sedimentation from developmental activities (projects), eutrophication from sewage and agriculture, physical impact of maritime activities, dredging, collecting, and destructive fishing practices, pollution from industrial sources and oil refineries and the synergistic impacts of anthropogenic disturbance.

Fishing is a major activity, and at present in the 3,651 fishing villages situated along the 8,129 km coastline of India, about one million are occupied in full time marine capture fisheries. The value of the annual marine fish production of 4.6 m t during the year 2002–2003 and the value of marine products export were US $152.92 m. This is mainly due to the introduction of bottom trawlers, into Indian waters in the early 1960s. Several types of net fishing have also been responsible for the over-exploitation of marine resource. Along with increase in the targeted catch, a number of untargeted fish and other biota are removed from their habitat and discarded as waste (trash fish). Shrimp trawlers probably have the highest rate of by catch bringing in up to 90% more of “trash fish”. A total of 1,006 purse seines in India employed for fishing may have the same effect on the seabed as that of the trawl netting. Random capture techniques employed in India destroy immature fish and other non-targeted marine species. Gill nets used to catch fish bring in a host of other animals such as dolphins, turtles, etc. Because of the large size of the areas concerned (Gulf of Mannar and Andaman and Nicobar Islands or other areas in India), and the general lack of resources for enforcement, awareness education appears to be more successful than legislation in controlling these activities.

Although now illegal, blast fishing has been a widespread fishing technique in India. Schooling reef fishes are located visually, after which the capture boat moves within close range and a lighted bomb is thrown into the middle of the school. Due to blasting, branching, tabulate and foliose hard corals are shattered while massive and columnar corals are often fractured. Bombs made of chemical fertilizers such as ammonium/potassium nitrate were confiscated from the foreign poachers apprehended in Andaman and Nicobar Islands. Gelatin sticks were observed to be used to blast fish by the fishermen around Gulf of Mannar reefs (Venkataraman et al., 2003).

Sedimentation throughout the coast of India physically interferes with the recruitment of coral larvae, which require a solid substratum upon which to settle and metamorphose. Illegal sand mining in Andaman Islands and illegal coral quarrying in Gulf of Mannar (Tuticorin group of Islands) and some islands of Gulf of Kachchh have caused a lot of sedimentation and siltation on coral reefs.

There has been unprecedented bleaching of hard and soft corals throughout the coral reefs of the world from mid 1997 to late 1998 (Wilkinson, 1998, 2000). Most of the corals in the coral reefs of India have been adversely affected during the bleaching in 1998, which destroyed most shallow water corals. This event has greatly reduced live coral cover in the reef (Venkataraman, 2000). Study conducted after or during the bleaching event reported a reduction in live cover of corals in Gulf of Kachchh (20–40%), Gulf of Mannar (20–40%), Lakshadweep (20–30%) and Andaman and Nicobar Islands (<10%). The live coral cover in Andaman and Nicobar Islands was between 50–75%, which is very high when compared to other reefs in the Indo-Pacific region (Muley et al., 2000, Rajasurya et al., 2002).

In addition to natural and human induced coral degradation, coral diseases are considered to be one of the major problems faced by the coral reefs in recent years. Necrotic lesions, fleshy algal over-growth, black band disease, and white band disease have been reported from the Andaman and Nicobar and Lakshadweep Islands. In addition, a new disease called pink line disease has also been reported recently from Lakshadweep (Ravindran and Raghukumar, 2006).

The coral eating starfish, Acanthaster planci was the focus in the late 1980’s and early 1990’s in the Andaman and Nicobar Islands as well as in other coral reef areas of India (Venkataraman and Rajan, 1995). Although sediment core data have indicated Acanthaster outbreaks 10,000 years ago, recent studies have shown a relationship between nutrient input and recruitment success of the larvae. Studies on echinoderm reproduction have demonstrated that the success of the recruitment of their planktonic larvae depends on phytoplankton availability following spawning.

Coral damage from the Tsunami of 26th December, 2004

The major damage to reefs is caused by storms, particularly tropical cyclones and by tsunami. These cause major intermittent damage to reefs, particularly to those reefs that rarely experience these storms. Due to a 1969 cyclone, a large area of coral was buried under sand in the Rameswaram area of the Gulf of Mannar. Likewise, the cyclone of December 1987 in the Bay of Bengal devastated the coral reefs of the Mahatma Gandhi Marine National Park of Port Blair, Andaman that resulted in piles of broken coral colonies scattered near the shore.

A very severe earthquake with a magnitude of 9.0 on Richter scale struck northern Sumatra, Indonesia on 26th December, 2004, and it was widely felt along the east coast of India. In Tamil Nadu, people felt distinct tremors in many parts of Chennai. The quake was also felt along the Coromandel Coast up to some areas in Vizakapatinam. The devastating tidal waves consequent to the earthquake lashed several coastal districts of Tamil Nadu and Puducherry as well as the archipelagos of the Andaman and Nicobar Islands. The Nicobar Islands were most severely hit given their proximity to the island of Sumatra and the epicenter of the earthquake. It is reported that shallow water coral reefs in the Andaman Islands have been exposed 2 m above the water mark (Figure 3) whereas the Nicobar group are submerged 2.0 m below the water mark (Venkataraman, 2006).

Conservation

India has 36 marine protected areas of which 20 are entirely located in intertidal/subtidal or seawater-mangroves, coral reefs, lagoons, estuaries, beaches, etc., and 13 having major parts in marine ecosystem and some part in terrestrial ecosystem (Singh, 2002). The Wildlife Protection Act, 1972 provides protection for these areas and certain marine species. Corals are protected under this act. India’s Coastal Regulation Zone Notification (1991) regulates onshore development activities, which affect coastal environments. Coral reef conservation is also included in the Environmental Protection Act (1986), the National Conservation Strategy and Policy Statement on Environmental Development (1992) and the Action Plan of the Ministry of Environment and Forests.

Conclusion

Coral reefs in India have drawn great attention from the eighteenth century onwards. This was achieved from many surveys and expeditions conducted by foreigners, in particular by the British. The introduction of Surgeon Naturalists in the expedition ships helped marine research to flourish in varied fields of fauna and flora. However, in India, major studies have been conducted only on the commercially important organisms such as crustaceans, molluscs, holothurians, and higher vertebrates. Many minor phyla which are not commercially important have not been studied so far. For example, species of different minor phyla that live as the interstitial fauna of coral reef areas have not been studied till date, due to a lack of expertise in this field. Though taxonomy is being taught as a subject in the curricula of schools and colleges, there is no committed institution for the learning of taxonomy except survey departments under the placard of the Government of India. Probably, more than 75% of the biodiversity of coral reefs of the Andaman and Nicobar and Lakshadweep is not yet studied. This is mainly attributed not only to the decline in the number of taxonomists but also due to the lack of facilities. Geological and geomorphological studies are probably even less advanced which is unfortunate given the wide geographical distribution of coral reefs in India.

Cross-references

Eastern Indian Ocean – Northern Sector

Indian Ocean Reefs

Maldives

Tropical Cyclone/Hurricane

Tsunami

Western Indian Ocean