Past periods of rapid global warming such as the Paleocene–Eocene Thermal Maximum are used to study biotic response to climate change. We show that very high peak PETM temperatures in the tropical Atlantic (~ 37 ºC) caused heat stress in several marine plankton groups. However, only slightly cooler temperatures afterwards allowed highly diverse plankton communities to bloom. This shows that tropical plankton communities may be susceptible to extreme warming, but may also recover rapidly.