Why did warm-water planktonic foraminiferans become more common in oceans during the Holocene?

During the Holocene Epoch, warm-water planktonic foraminiferans became more common in the oceans primarily due to the global warming that followed the end of the last glacial stage. As the climate transitioned from the cold conditions of the Pleistocene to the warmer Holocene, these organisms responded to the rising water temperatures by migrating poleward—in some cases by distances of 1,000 to 3,000 kilometres—to remain within their optimal temperature habitats.1

Because marine organisms are highly sensitive to water temperature, depth, and salinity, their distribution in deep-sea cores serves as a reliable indicator of past oceanic conditions. Studies of globigerina ooze show that approximately 10,000–11,000 years ago, there was a marked increase in the relative number of warm-water foraminiferans. Additionally, some species exhibited physiological changes, such as shifting their coiling direction from left-handed to right-handed spirals, as a reaction to the environmental stress of warming waters.231