Climate Change Could Cause Tropical Plankton Exodus

December 12, 2023

Modern plankton biodiversity in the tropics is a surprisingly recent development and the result of 8 million years of global cooling, according to a study led by researchers at the University of Texas Institute for Geophysics (UTIG.)

The finding raises concerns that rapid ocean warming could force plankton, which form the base of marine food chains, to move away from the tropics. This would negatively affect ocean ecosystems, including those of important fish such as tuna and billfish, and coastal communities that depend on them.

The research was published in the journal Nature.

Using microfossils to track the history of a group of zooplankton called Foraminifera, the researchers found that the last time Earth was this warm — just before global cooling began 8 million years ago — tropical plankton populations lived in waters more than 2,000 miles from where they are today. The natural cooling of the past 8 million years that allowed the plankton to flourish in the tropics has been reversed by climate change during the past century.

“Earth’s current biosphere evolved for ice ages,” said lead author Adam Woodhouse, a UTIG postdoctoral fellow. “By suddenly switching to an Earth of 8 million years ago, we’re not just killing off a few species, we’re changing the entire chemistry of the atmosphere and oceans, and nothing is ready for that.”

The findings suggest that plankton species could evacuate the equator and head poleward, researchers said. Other studies of modern plankton have already documented signs of this happening. Researchers fear that the loss of diversity in plankton populations could trigger a cascade of extinctions like those seen in rainforests after logging and fires.