On 26th December 2004, an earthquake measuring 8.9 on the Richter scale hit the region. This was due to substantial tectonic activity in the region. Due to the same, low lying areas from South Andaman to Nicobar group of islands have been submerged from 1-4 meters. However large areas including reefs were uplifted in the northern group of islands. Soon after the earthquake, a tsunami of 2 to 10 meters followed in South Andaman to Nicobar Islands. This caused a huge loss of human lives and infrastructure destruction in the islands. The impact continues to affect peoples’ lives as basic infrastructure such as roads, jetties have been destroyed. Sea water has entered paddy fields and houses and inundation continues during high tides.

The impact of tsunami is also very visible on coral reefs and coastal habitat. Prone areas for the negative impacts mainly are coastal habitats, coral reefs, sea grass and turtle nesting sites.

The tsunami had washed away several important turtle nesting beaches in Nicobar Islands. However, several new beaches are formed in these islands and some cases of turtle nesting has been reported. Fortunately, one of the important Leatherback turtle nesting sites in M. G. Marine National Park survived the tsunami.

Huge deposition of sand is expected to have happened on sea grass beds due to the tsunami. This will have a long term impact on the population of dugongs. On 16th February, there was a sighting of 5 dugongs in one herd in North West coast of South Andaman. One salt water crocodile was sighted attacking dugong in same area. It is feared that the population of the Giant Robber Crab must have dwindled as this crab’s habitat is mainly coastal areas. The distribution of robber crab ranges mainly in Nicobar group of islands.

Outcome of surveys in brief
Jolly Buoys: Coral reefs of this island have been extensively damaged. In reef flat sand/silt is deposited on coral reefs. Several large colonies (larger than 2 meter in diameter) have been uprooted and scattered all over the reef, coral colonies occurring on reef edge have pushed to the deeper water up to 20 meter, broken branches of Acropora and Hydnophora rigida scattered all over, visibility is reduced, fish abundance and diversity has reduced, logs and other debris originated from the land has been found on reefs.

Redskin: As in the case of Jolly Buoys, the reef is largely destroyed. This reef is mainly dominated by massive Porites lutea. On reef flat, corals had little damage. However the colonies have shifted to the reef slope. Some colonies are also found at the depth of 15 meter. Visibility has been reduced. The beach width has been reduced and the beach slope has increased.

Alexandra: Compared to Jolly Buoys and Redskin, damage is lower but visibility has reduced substantially. The corals beyond 15 meter have sand/silt deposits. This reef earlier was dominated by Porites and Acropora however the species that suffered most is Acropora. A few colonies of Porites lutea have been uprooted.

Grub: Interestingly, this area had very minimal impact of tsunami. Large colonies of Acropora (fig 1) are still in excellent condition. Earlier Porites, Acropora and Echinopora lamellosa dominated the reef. Presently it appears that Acropora has been increased. Due to the tsunami, a few colonies of Acropora, Porites, Echinopora and Psammacora have been broken / toppled.

North Bay: This area is closer to Port Blair and the tsunami had very little impact on the reefs. However the topography and composition of beach has changed. This reef is dominated by Porites lutea, Porites nigrescens and Acropora. There are a few sightings of breakage of the Porites nigrescens and Acropora.

Conclusion and Recommendations
This is a natural disaster and evolution point of view; coral reefs have been affected before with this kind of phenomena and have coped and survived. However, from the human point of view there might be an immediate impact on humans. Devastated coral reefs mean reduced natural protection from turbulent sea in the monsoon leading to increased erosion of coastal areas. The destruction of reef will also have a negative impact on fisheries and tourism in this island as both these sectors substantially depend on the coral reefs. To speed up recovery, certain initiatives must be taken such as removal of debris from the reef, overturning toppled colonies and transplantation of broken branches of corals like Acropora. This may be initiated in M. G. Marine National Park in the first phase then could be applied to other devastated coral reefs. This will help coral reefs to have a speedy recovery.