How fast do these creatures reproduce? Are they going to generate billions in between now and the next hot season? How many more will die this hot season? Will even more die next hot season?
It doesn’t have to reproduce right away, that’s just unrealistic. But the larger amounts of free space will mean a land grab by the survivors. That’s how it works in nature.
If the climate changes and the water heats up then the ecosystem will be replaced by those animals that would survive in warmer water. That’s science.
(Meanwhile poor humans are trying to grow crops and raise animals. We may get very hungry, for decades)
You could look to the intertidal regions near the equator for more reasonable comparison. They are much less rich in life compared to the waters around Vancouver.
The point others and I are making is that life does not expand arbitrarily, or in a weaker form, the life that may expand will be a much less desirable environment for us humans than the present.
Even though you deny it, we can very simply create environments, right here on earth, where life as we know it will not be possible. Look into an operating steel smelter for example, just to remove any subtlety and ambiguity.
Sure, maybe ‘Science’ can replace all of our biosphere with extremophiles, but I for one do not desire to live in such a world. I like trees and birds and mammals and lizards and (you get the point).
It's july 18. It both is hot season and was an abnormal heat wave.
So the questions are valid.