The PEMEX accident, in 1979, streamed oil into the Gulf of Mexico for almost 10 months. I’d be curious to know how the area around it was affected, ecologically.
I suspect the catastrophic effects of this are being overblown. We're already seeing some of these Gulf coast state governors complaining that the media is making people believe the beaches are all covered with oil, when in fact few if any are.
Some level of crude oil leaks into the oceans constantly and naturally, and the ocean can handle it. Obviously a large amount in a confined space can overwhelm natures ability to deal with it for awhile, but the Gulf will survive just fine.