Corals in shells of death

The shores of the Andaman and Nicobar islands are losing their magnificent coral reefs because of heavy siltation caused by developmental activities

 
Last Updated: Saturday 04 July 2015

-- WIDESPREAD deforestation and heavy siltation are steadily destroying the beautiful, but ecologically fragile, coral reefs of the Andaman and Nicobar archipelago.

The islands experience high rainfall, 50 per cent to 90 per cent of which runs off into the sea. Bad land use practices result in high turbidity which then acts as a barrier to sunlight, so vital for photosynthesis by the living corals. This results in reduced oxygen in the water, eventually leading to coral death.

A survey carried out by the Madras chapter of the Indian National Trust for Art and Cultural Heritage (INTACH) found that, on an average, only 1.3 per cent of all the coral reefs in the archipelago were in excellent condition, while about one-third were in a good state. Some 14 per cent reefs were in very poor condition with over 75 per cent of the corals dead. In Little Andaman, as much as 67 per cent of the coral reefs were in the poor slot.

These endangered reefs, which are home to 135 species in the Andamans and 103 in the Nicobars, have attracted little research in the past. The reefs abound in commercially-valuable molluscs like the giant clam, different kinds of shells, cowries, pearl oysters, and starfish. The present study is the first of its kind in the region.

During the monsoons, sea water becomes muddy to a distance of about 200 m to 300 m from the shore near deforested and freshly cleared agricultural areas. Suspended silt load ranged from 0.1 mg/litre to 1.6 mg/litre of sea water.

The fringe reefs around South Andaman, particularly at Port Blair, have suffered much due to developmental activities such as construction of roads, wharfs, jetties, navigation of large ships and oil spills. Besides, pollution from sewage disposal, discharge of effluents by timber industries and an expanding population are taking their own toll. The population of the Andaman and Nicobar islands has already reached about 3,50,000.

The problem is compounded by the felling of mangrove trees, which trap silt in their roots, along the creeks and bays. Reefs are not isolated ecosystems. They depend on mangroves to reduce tidal currents and to provide a good habitat and breeding ground to many reef species.

Despite a ban on collection of small coral blocks and rubble for construction of roads, the survey has found that the practice continues blatantly near the Nancowry settlement. A shortage of hard rock for road construction had started this destructive practice of using "the cheapest, locally available material."

Another threat to the reefs is the Crown of Thorns starfish (Anthacaster planci). This starfish has destroyed reefs in many parts of the world. The study has recommended monitoring of the starfish population though only a small number has been sighted yet. Nocturnal observations are needed to get a more accurate assessment.

According to the study, the Andaman and Nicobar coral reefs can still be saved. But this will need environmentally-sound farming practices, phasing out of timber-based industries, afforestation, checking the island's population and banning the exploitation of endangered marine life like sharks and sea turtles. More precisely, a strong authority responsible for both research and protection is the most urgent requirement of the coral reefs right now.

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