None of the dolphins kept in The Living Seas would be able to survive in the wild, as they've all been born in captivity. Not sure about Sea World, but I imagine that's the case there as well. Most reputable aquariums and aquatic parks haven't taken animals out of the wild in years, in some cases, decades. Their captive breeding programs are more than sufficient. The manatees that are kept in The Living Seas are only there for a few months, then they're released. They're rescued, rehabilitated, then released back in to the wild.
I think we could all agree that removing healthy dolphins from the wild for the purposes of entertainment is cruel. If that's what was occurring, I'd be the first one to sign that petition. Heck, I'd help circulate it. However, that's not the case here.