During the Gulf War, the Iraqis opened the valves on wells and tankers in the Persian Gulf. 11 million tons of oil went into the water. And there was a study done earlier this year that shows that it's had very little measurable effect on the ecosystem.
There was a vastly larger oil spill off Mexico back in the 80s and it has had zero long term effect. People who are worried about this very very very small spill--look at wiki for a list of the biggest--are ignorant fools.