I was about to ask, “What does this have to do with Toba?” But you beat me to it. True, the earth was already in an Ice Age at that point, but if you look at long term temperature charts you can see a significant dip after 74,000 ya.
I don’t know when temperatures hit their maximum low, but glaciers did not reach maximum until 20,000 years ago.
About 19,000 years ago, CO2 reached its maximum low around 180 ppm, which I believe is still the all time record low, at least in “modern” times.
The consensus is that 150 ppm is the tipping point where most plants and trees would die, which, of course, means that almost all large herbivores and carnivores would die, too.
I’m not sure what 150 ppm would mean for sea life, but phytoplankton, which need sunlight and CO2, are the first link in the food chain for most sea life.