CHITTAGONG: An oil spill on a river in southeast Bangladesh has threatened the breeding ground of the critically endangered Ganges dolphin, environmentalists said on Sunday, describing it as a “major disaster” for the mammal.

A tanker carrying 1,200 tonnes of diesel collided with another ship on the Karnaphuli river near Chittagong port on Friday and spilled tonnes of fuel, port authority spokesman Omar Faruk said.

At least 10 tonnes of diesel spread across an area of 16 kilometres, he added, but local media said the amount spilled was likely to be far higher.

Environmentalists said the spillage posed a “serious threat to the marine biodiversity in the river”, particularly for some 60 freshwater dolphins who use the area as their breeding ground. Marine science expert Shafiqul Islam said it was a “major disaster” for the river’s dolphin population as they could inhale toxic petroleum vapours while surfacing to breathe.

“The dolphins could experience both acute and chronic exposure through their respiratory system and through ingestion of contaminated prey,” he said.

Karnaphuli — a key breeding ground for the dolphins — experienced a similar accident in 2016.

The dolphin population is already threatened by nets used to catch fish and shrimp. In the past four years at least 20 dolphins died unnaturally — mostly through pollution — in the Karnaphuli and the adjacent Halda river.

Senior port authority official Faridul Alam said most of the oil had been cleaned up, saying it was given “high importance” due to the dolphin breeding zone.

Bangladesh banned ship movement in major rivers in the country’s southwestern mangroves in 2014 after a oil spillage occurred at the heart of an Irrawaddy dolphin sanctuary.

Published in Dawn, October 28th, 2019