Roughly 3 billion years ago, a single-celled photosynthetic bacterium began burping a new chemical that was poisonous to nearly every species on Earth. Over the following hundreds of millions of years, more microorganisms began producing this toxic gas, first saturating Earth's oceans and eventually its atmosphere. Up here, this chemical changed the composition of pre-existing gases so drastically that it caused a global ice age. And the name of this powerful, poisonous, world-changing gas? Oxyg
I mean, sure. We’d deserve it for striking first.
Edit: I misunderstood your comment. I see it now :)
My bad. I meant the “lethal” in the title. Title makes it sound as if a deadly pandemic happens if that lake thaws.