Individual reefs probably would not have survived. The polyps would have taken root elsewhere (probably closer to the equator in ice ages). The organisms have e

Individual reefs probably would not have survived. The polyps would have taken root elsewhere (probably closer to the equator in ice ages). The organisms have evolved over millions of years and are clearly hardy to drastic climate change. The issue is that the reefs themselves will certainly die and big, new ones won't form for thousands of years. So from our point of view, they're "extinct".