If the tanks hold up, and they likely will.
The oil will be OK.
If it leaks out slowly, it will be bio degraded over years.
Then again, there could be a rupture and it could all come out quickly and create a big problem. It is heavy bunkers, and in the cold atlantic, it may stay under water until destroyed by bateria.
All I am saying is that while it is certainly a huge problem, it is by no means a huge disaster yet, and may not become one.
Ed