1. 3.2 billion barrels translates into a bit less than 200 billion gallons.
2. The Gulf contains roughly 643 Quadrillion gallons of water http://www.gulfbase.org/facts.php
3. Which means that one is altering less than 1 ppm if my math is correct. I’d guess that one would not be altering content in an even manner.
I think it was once described by Rush as a single drop from an eye dropper into a full bathtub.