It's likely that the dolphins will make the next evolutionary jump to develoup great intelligence and psychokinesis, large dorsal fins, and the ability to fly in the sky due to the biological develoupment of helium sacs. Also, the ocean has developed it's own mind.
It's all right here, in this picture:
The reason why the smaller dolphin does not have the aformentioned features (minus the telekinesis) is just because he's a time traveler. This does not weaken the credibility of my assertion.
Now, when this smaller dolphin (lets call him "Ecco") traveled into the future, he created a split in the timeline. One future is a world of psychic flying dolphins and waterways extending into the sky, while the other is "a dead, mechanical world, sucked dry by the Vortex":
Hopefully Ecco will be able to take care of that...