I will comment that while an observation such as a microbial mat the size of Greece is surprising, it is not unexpected. I’ll also note that the recent emphasis on the fundamental importance of microbes as the biogeochemical “engines” of ecosystems is spot on, but it shouldn’t be construed that microbes do it all. I don’t think that there has been enough consideration of the dependence of modern microbial communities on the other end of the size/trophic spectrum. What does a soil microbe community on the African savannah look like without large biomass movers like elephants and wildebeest? How have benthic microbial communities in the North Atlantic changed since the historic extinction of the Atlantic Gray Whale?