Impact of the December 24, 2004 Tsunami on Coral Reefs of Andaman and Nicobar Islands, India

CURRENTS vide are compromised. Management reef sites over the past few years ac- Gustavo A. Paredes via marine reserves must be applied tually persist and extend to other Ca- Center for Marine Conservation and in conjunction with other conserva- r ibbean reefs. We believe that only a Biodiversity tion actions such as the improvement multinational Caribbean-wide conser- Scripps Institution of Oceanography of the water quality and run-off con- vation strategy will ensure the survival University of California San Diego trol. We must ensure that the sporadic of these ecosystems. 9500 Gilman Dr. events of recovery revealed in some La Jolla, CA 92093-0208 Impact of the December 24, 2004 Tsunami on coral reefs of Andaman and Nicobar Islands, India The Andaman & Nicobar Islands man and Nicobar islands. As per the tsunami-victims have been in 207 relief are a low mountainous chain of is- year 2001 census, 25 islands in Anda- camps. lands, which rise from a submerged man group and 13 islands in Nicobar The Indian Ocean tsunami caused north-south trending ridge separat- group are inhabited with a total pop- extensive damage to coral reefs of the ing the Andaman Sea from the Bay ulation of 356,265 people. Recently Andaman and Nicobar islands. Most of Bengal between 6°45ʹ13ʹʹ.41 N and there was an undersea earthquake in of the islands’ coastline was eroded 92°12ʹ93ʹʹ.57 E. This island group in- the Indian Ocean. A rupture occurred by the tsunami surge and sediments cludes 306 islands and 226 rocks, with off Banda Aceh in northern Sumatra were dumped on adjacent reefs. a coastline of about 1962 kilometers. (3°09’ N, 940 26’ E) at 00:58:49 GMT These island reefs were not affected The islands located north of 10° N Lati- (06:28:51hrs IST) on Sunday Decem- by the bleaching event in 1998. It has tude are known as Andamans (Figure ber 26, 2004, with a magnitude of been found that the area has moved 1) while those located south of 10° N Mw = 9.3. The rupture spread north- southwestward about 4-5 meters at Latitude are called Nicobars with a total ward at roughly 2.8 km s-1 for approxi- North Andaman (Diglipur), about 4.5 area of 8249 square kilometers. These mately 8 minutes over a 1300 km-long meters at Middle Andaman and about islands are supposed to have arisen aftershock zone. Comparisons with 3 - 4.5 meters at South Andaman. In from the ocean bed in the Mesozoic the aftershock areas of other great addition to this the North Andaman period about 110 million years ago and earthquakes indicate that the Suma- landmass was lifted up by 0.60-0.90 have since then undergone several tra-Andaman earthquake did indeed cm resulting in a fall in the water level. periods of partial submergence and have a moment magnitude of ~9.3. Due to this, almost all reef fl ats on elevation. Fringing, Patch and Barrier Its rupture, in both reefs are present here, covering about duration and ex- 948.8 square kilometers. The total tent, is the longest mangrove area is approximately 762 ever recorded.1 The km2. There are 106 Protected Areas, earthquake gen- 96 designated as wildlife sanctuaries, erated a tsunami 9 National Parks and one Biosphere surge that was reserve. Among the 9 National Parks, among the dead- 2 are Marine National Parks (Mahatma liest disasters in Gandhi Marine National Park and Rani modern history. Ac- Jhansi Marine National Park). cording to offi cial 6000 species were recorded from data, the tsunami Andaman & Nicobar Islands, amount- took a toll of 3513 ing to 7.5% of the total Indian fauna lives, including 1177 (3% of the Terrestrial Fauna and 4.6% children. About 350 of Marine Fauna). So far 235 species children were or- of scleractinian corals, 111 species of phaned and 85 of soft corals, 112 species of sponges, the 322 government 411 species of crustaceans, 1422 schools on the is- species of mollusks, 425 species of lands were washed echinoderms, 750 species of fi shes, away, another 34 14 species of reptiles, 50 species of were left com- marine birds and 64 species of al- pletely dilapidated. gae have been reported from Anda- As many as 46,000 Figure 1. Map of Andaman & Nicobar Islands. Reef Encounter 34, May 2007 25 CURRENTS Figure 4. Incredible coral damage around North Reef. Figures 2&3. Mass mortality of corals on reef fl at at Anderson Island. Figure 5. Mass mortality of corals at reef fl ats of Interview Is- land. the western side of northern group by 1-2 m, and seawater inundated Bay reefs, overturning of large corals of islands (i.e west coast of Interview the agriculture fi elds and coastal especially Porites lutea colonies was Island, North Reef Island, Latouche mangroves. The western coast of the observed. There was more damage Island, South Reef Island, West Is- North Sentinel Island, which is further on the northeastern side of Jolly Buoy land, Landfall Island, East Island and south in South Andaman, was uplifted Island where nearly 10m2 of reef area Anderson Island) were exposed and by half a meter. was covered by sand. The Jolly Buoy dried up (Fig 2-5). Almost all corals Extensive coral reef surveys were Island lies in a northeast/southwest di- in the reef fl ats and other associated made at Mahatma Gandhi Marine rection. On the northeastern side, the fauna seemed dead beyond regener- National Park at South Andaman dur- beaches and near shore land areas ation, appearing like a graveyards of ing the month of January 2005 using were around 6-10 m wide and were corals. The corals in reef slope were SCUBA diving and snorkeling. It con- devastated by the tsunami. At one not as affected by the tsunami and sists of 15 islands of different sizes, site, nearly 20m2 area of coral reef was the live coral percentage is 55-60%. scattered over a total area of 281.50 buried under the sediment and no cor- In contrast, South Andaman subsided km2. In Jolly Buoy, Redskin and North als were visible. Most of the branching 26 Reef En coun ter 34, May 2007 CURRENTS Figure 6. Overturned massive coral Porites lutea. Figure 9. Sand deposited over on coral beds in MG National Park. Figure 10. Sand deposition on Porites colonies in MG National Park. corals belonging to the genera Acro- pora, Hydnophora and Montipora were broken into small pieces and some washed away. Large size boul- der corals, Porites spp., (more than 1m wide), were overturned and most of the colonies were uprooted (Fig 6- 8). Some colonies were completely buried under sediment excepting the top portion (Fig 9&10). The island reef was remarkable for its richness of mushroom coral species belonging to the family Fungiidae. Most of these Figure 7&8. Uprooted massive coral Porites lutea. Reef Encounter 34, May 2007 27 CURRENTS Figure11. Massive Porites coral washed to the Land of Car Nicobar Island. specimens were washed away by the The corals around the Nicobar fected by tsunami and 20,000 coco- tsunami and existing live mushroom group of islands were extensively nut trees were uprooted. The corals corals were suffocated by sedimenta- damaged due to heavy sand and silt were washed away onto the land at tion and likely result in death. The sur- deposits brought by tsunami waves. Car Nicobar island(Fig 11&12). The vey showed 50% mortality in north- The Nicobar Islands include serpen- tsunami caused the worst damage eastern reef of Jolly Buoy Island. The tine gabbros, marine deposits of the to this island and the wave reached reef at the southwestern side was not late Tertiary including sandstones, almost more than 7 meters in height. much affected by the tsunami, and slates, clay marls and plastic clays The area between 7°45ʹ–8°15ʹN and the reef slope corals were in pristine and coral reefs of recent origin. About 93°25ʹ–93°40ʹE consists of Camorta, condition. 6000 ha of coconut gardens were af- Trinkat, Nancowry, and the Katchall 28 Reef En coun ter 34, May 2007 CURRENTS Figure 12. Uprooted coconut trees along with coral fossils in Car Nicobar Island. islands. Extensive coral reef fl ats of groves and 94% of mangroves were 3 meters affected the Great Nicobar about 2.5 km2 occur at the northeast- submerged. On Katchall Island alone Island and a maximum down throw ern and northwestern side of the Cam- 1550 ha, or 38% of mangroves were at Indira Point (Southern most land orta Island. These reefs were severely submerged. The coral reefs of these part of India). The lighthouse on Indira damaged by the earthquake and tsu- islands somehow played an important point and the adjacent land are still un- nami. On the northeastern side about role in attenuating the tsunami wave der the sea. Large amount of mud and 2.0 km2 of landmass was eroded and height, thus lessening its destruc- trees settled down over the reef fl ats all sediments were dumped onto the tive effects. Similar phenomena were smothering the corals. The corals in reef. The reef fl ats around the Trinkat observed in the Philippines during the reef fl ats of Great Nicobar Islands, Island extend up to 2.5-3.0 km2 from 1992.2 particularly on the western side, were shore. Due to the earthquake and Detailed coral reef survey in Great in pristine condition before the tsu- tsunami the island was divided into Nicobar Island showed the live coral nami.

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