Oil from a barge that sank in a bay off the Bulgarian section of the Danube is in danger of leaking into the main river, posing "potentially serious" consequences, environmental group WWF said Wednesday.
The vessel went under on November 9 with around 20 tonnes of fuel in its tanks in a small bay near Bulgaria's largest Danube port of Ruse while unloading firewood, but news of the accident broke only late on Tuesday.
Ruse maritime administration chief Georgy Ivanov said Wednesday that authorities have managed to contain any pollution from the vessel within the bay, although attempts to pump out the fuel have failed so far.
"For the time being there is no oil spill in the Danube river itself," he told state BNT television.
Petrochemical spills form a thin, monomolecular film on the surface of water, stopping oxygen from penetrating and causing fish and other aquatic organisms to suffocate, WWF said.
"Some of the most valuable riparian wetlands in Bulgaria and in the lower Danube, such as Kalimok Marsh and Srebarna Lake, are situated downstream of Ruse and the 10-day delay in disclosing news of the spill may mean that it is already too late to protect these areas," Stoyan Mihov from the WWF said.
Oil slicks also cause birds' feathers to stick and cease to be waterproof while toxicity can also kill birds directly, the group added.
Explore further: Danube's near-record lows strangle shipping