Scientists bring oxygen back to dead fjord

So is this fjord naturally anaerobic, or is this some sort of remediation for some damage we caused? All it says is that climate change will "increase of this phenomenon in the future," not the history of this particular site.

Far from reviving from the dead, it seems likely that we're just replacing one ecosystem with another. How many species are unique to that habitat?

If you think the idea of humanity wiping out an entire biome and its associated species seems absurd, look at what agriculture has done to Earth's grasslands.