Indian Coast Guard  /  AP file
The retreat of the ocean’s waters from North Sentinel Island in India’s Andaman and Nicobar archipelago after the tsunami exposed the coral reefs in the foreground in this Dec. 28 photo released by the Indian Coast Guard.
updated 1/6/2005 10:07:00 PM ET 2005-01-07T03:07:00

The tsunami that took a heavy toll in human life also battered Indian Ocean coral reefs that already were in distress from pollution and global warming, possibly causing damage that will require decades to recover, experts say.

Scientists have yet to conduct a complete survey of damage to the coral reefs from the tsunami, but experts fear that some of the Earth’s most spectacular coral formations may carry scars from the killer wave for many years.

Tom Hourigan, a coral reef expert for the National Marine Fisheries Service, said that coral formations throughout the Indian Ocean were severely damaged by El Nino warming in 1997 and 1998 and were just beginning to recover when they were slammed by the tsunami last month.

“It is very likely that the tsunami would damage the coral and some of the worst damage would come from debris thrown up against the reefs,” said Hourigan.

‘One-two tsunami punch’
He said the shallow reefs along hundreds of miles of beach in Indian Ocean would be victimized by a “one-two tsunami punch.”

First, the tsunami wave would rise as it entered shallow water and smash into the coral reef, said Hourigan. The force of the wave itself could damage the reef. But then would come the second punch. As the wave swept back into the ocean, it would carry tons of debris — including cars, trees, refrigerators and furniture — along with sludge and silt.

The heavy debris would hit the reefs like battering rams, bulldozing the fragile coral formations. The sludge can bury the coral, suffocating it.

“One of the biggest impacts will be from the debris pulled off the land onto the reefs,” said Hourigan. “We’ve been doing quite a bit of work in the western Hawaiian islands in removing debris. It is likely that a lot of debris coming off the land will be damaging to the reefs.”

He said studies following typhoons in Guam showed that tin roofs blown onto coral caused significant damage when ordinary wave action caused the tin to grind away at the reef.

Some minor damage is repaired by the coral fairly quickly, but major reef destruction can take decades to heal, he said.

Coral disease, death possible
Coral reefs also may suffer more diseases and even death from the silt and sand that chokes the tiny organisms that builds the reefs.

“Some entire reef ... ecosystems could have been buried by sediments flushed into shallow environments,” said Russel E. Brainard, chief of the coral reef division of the National Oceanographic and Atmospheric Administration Pacific Islands Fisheries Science Center in Honolulu. For reefs normally washed by high tidal action, this sediment could be swept clean within weeks or months. But in reef areas protected from tidal waves or currents, the cleansing could take years or decades, Brainard said in an e-mail.

As tsunami waves retreat to the ocean, they also flushed off the land oils, paints and other hazardous chemicals, said Brainard.

“All of these chemicals are now in the near shore ecosystems interacting with all types of marine life,” he said. “These stressors could result in diseases to corals, algae, fish and other (organisms). The impacts could be long lived.

Brainard said that plastics, including such things as fishing nets, fish line and traps, are also washed into coral reefs and the near shore environment. Such plastics will last in the marine environment for years, even decades, he said.

The loss of coral reefs could severely reduce the amount of fish available to some small, oceanside rural communities in Asia and Africa that depend on the sea for food.

“The three-dimension structure of a coral reef is the most important factor in the richnesses you see on a reef,” said Hourigan. “Fish depend on it for hiding places, for the prey they feed on.

“A large amount of the protein that human communities need come from fishing on the coral reefs,” he said. If the reefs are severely damaged, then this could affect the fish population “and have an impact on those communities for a long period of time.”

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