Nice article, but that headline is so misleading, I'm not inclined to upvote it.

tl;dr: Microorganisms used to live without oxygen. Some organisms started sprewing oxygen. Oxygen killed off most of these oxygen-free microorganisms. Life evolved and adapted. There's this lake in which the bottom layer is oxygen-less and oxygen-free microorganisms exist there. Scientists are doing a bunch of studies of this ecosystem.

I wouldn't call those organisms "alien." They were first in this planet!