The discovery raises intriguing new questions about the role wildfires may play in spurring the growth of microscopic marine algae known as phytoplankton, which absorb large quantities of climate-warming carbon dioxide from Earth’s atmosphere through photosynthesis and are the foundation of the oceanic food web.
“Our results provide strong evidence that pyrogenic iron from wildfires can fertilize the oceans, potentially leading to a significant increase in carbon uptake by phytoplankton,” said Nicolas Cassar, professor of biogeochemistry at Duke’s Nicholas School of the Environment.
The algal blooms triggered by the Australian wildfires were so intense and extensive that the subsequent increase in photosynthesis may have temporarily offset a substantial fraction of the fires’ CO2 emissions, he said. But it’s still unclear how much of the carbon absorbed by that event, or by algal blooms triggered by other wildfires, remains safely stored away in the ocean and how much is released back into the atmosphere. Determining that is the next challenge, Cassar said.