Could oil improve the soil and help growth?

Oil is bad. Period. There is absolutely nothing good about it.

As per this one particularly bay, lagoon, whatever it is in those pictures, you have to ask some questions. How much oil did it get. Obviously, it wasn't much. Oil doesn't just go away, it grabs onto plants, animals, and eventually settles on the substrate. Also, where is this, specifically, with regard to passing Gulf currents or freshwater input, both of which would help to "flush" the lagoon (whatever).

Sure, it's possible that this area has a naturally rich substrate. Probably why it was green to begin with.

But miracle? No.

It's possible that the oil settled on the substrate at a "lucky" time, when the small plant shoots had already come up through the soil/water interface, and were big enough to reach the surface, but *after* the surface slick had "passed."

*If* this is a special, unusual thing happening, it's likely that luck more than anything else is at play.

Oil is bad, it carries toxin that are toxic to almost all life.

Oil does not and cannot not help with plant growth as oil does not contain the necessary nutrients for plant growth.