DHAKA (AFP) - Bangladeshi fishermen using sponges and sacks began cleaning up a huge oil spill in a protected area that is home to rare dolphins on Friday, after environmentalists warned of an ecological "catastrophe".
Thousands of litres of oil have spilled into the protected Sundarbans mangrove area, home to rare Irrawaddy and Ganges dolphins, since a tanker collided with another vessel on Tuesday.
The government has sent a ship carrying oil dispersants to the area, which is inside one of three sanctuaries set up for the dolphins.
But environmentalists say the chemicals could harm the delicate ecology of the Sundarbans, a UNESCO world heritage site.
The head of the local port authority told reporters that fishermen would use "sponges and sacks" to collect the spilled oil, which has already spread over an 80-kilometre area.
But Amir Hosain, chief forest official of the Sundarbans, admitted authorities were in the dark about what to do for the best.
"This catastrophe is unprecedented in the Sundarbans and we don't know how to tackle this," he told AFP. "We're worried about its long-term impact, because it happened in a fragile and sensitive mangrove ecosystem."
Rescue vessels have now salvaged the tanker, which was carrying an estimated 357,000 litres of oil when it sank.
But officials said the damage had already been done as the slick had spread to a second river and a network of canals in the Sundarbans, the world's largest mangrove forest, which straddles India and Bangladesh.
Rubayat Mansur, Bangladesh head of the New York-based Wildlife Conservation Society, said most of the oil appeared to have already leaked out.
"I visited the sunken trawler this morning. Only few hundred litres of oil remain inside, so almost all the oil has spilled into the Sundarbans," he said.
Mansur said oil dispersants were "not appropriate for the mangrove ecosystem" and urged local villagers to help collect the oil from nets that have been placed in the river to contain its spread.
Spread over 10,000 square kilometres, the Sundarbans is a UNESCO-listed World Heritage Site and home to hundreds of Bengal tigers. The delta comprises a network of rivers and canals.
Mansur said Bangladesh's coastal areas including the Sundarbans were the "largest known home" of the Irrawaddy dolphins.
"Irrawaddy Dolphins can be found in South East Asia. But their population size is very small compared to Bangladesh," said Mansur.
Bangladesh set up sanctuaries in the Sundarbans in 2011 after studies showed there were hundreds of endangered Irrawaddy and Ganges river dolphins there.
Fishing is banned, but tankers and other boats are allowed to pass through.