About 2,000 metric tons of oil, and almost 7,000 tons of sulfur in containers, were spilt into the sea amid a powerful storm on Sunday that killed at least six sailors, sank four ships and split open an oil tanker.
"Most of the fuel oil will settle on the bottom and will be thrown ashore gradually," said Vitaly Spiridonov of World Wildlife Fund Russia, adding that the seabed's fauna and flora would suffer the most.
The storm is continuing in the Kerch Strait, which links the Black Sea with the much smaller Sea of Azov, hindering the cleaning up effort.
"Oil products usually stay in the water for no more than six months," said Alexander Minin, a senior academician at the Institute of Global Climate and Ecology.
He also said the cyclone that had caused the storm in the Kerch Strait affected the area every year. However, he noted that it was moving further and further north, a phenomenon he put down to climate change.
The Environmental Watch on North Caucasus has said the accident was particularly devastating for the environment in the area as the Kerch Strait is the passage route for fish migration between the Black Sea and the Sea of Azov, including for many endangered fish species.