A crucial warning has been issued by scientists: our climate models are overlooking a vital component of Earth's climate system. These nearly invisible yet incredibly important players are calcifying plankton, microscopic organisms with a big role in regulating our planet's temperature. A recent study published in Science, led by researchers from the Institute of Environmental Science and Technology at the Universitat Autònoma de Barcelona (ICTA-UAB), highlights this oversight.
The study focuses on three key groups of calcifying plankton: coccolithophores, foraminifers, and pteropods. These tiny organisms, despite their size, have a massive impact on the global carbon cycle. By building shells made of calcium carbonate, they capture carbon and transport it through the ocean's depths, a process known as the ocean carbon pump. This pump is a critical regulator of Earth's climate, stabilizing it over long periods and influencing seawater chemistry and sediment formation.
"Plankton shells may be small, but their collective impact is massive," says Patrizia Ziveri, ICREA research professor at ICTA-UAB and lead author of the study. "By excluding them from climate models, we risk missing the bigger picture of how our planet responds to climate change."
One of the key processes missing from climate models is shallow dissolution. Much of the calcium carbonate produced by plankton doesn't make it to the ocean floor; instead, it dissolves in the upper ocean due to biological activities like predation, particle clumping, and microbial respiration. This shallow dissolution significantly alters ocean chemistry but is largely absent from major Earth System Models, potentially leading to inaccurate predictions of carbon movement and system responses to stress.
Furthermore, not all calcifying plankton behave identically. Each group has unique characteristics affecting their distribution, function in marine ecosystems, and vulnerability to climate change. Coccolithophores, the largest CaCO3 producers, are highly sensitive to ocean acidification due to their lack of specialized mechanisms for acidity removal. Foraminifers and pteropods, while possessing such mechanisms, face other threats like declining oxygen levels and rising temperatures. Treating these diverse groups as a single entity oversimplifies the ocean's response to climate pressures.
The authors emphasize the need to measure calcium carbonate production, dissolution, and export to deeper waters for each plankton group. Incorporating these details into climate models could enhance predictions of ocean-atmosphere interactions, long-term carbon storage, and the interpretation of sediment records for Earth's climate history. "By integrating calcifying plankton into climate models, we can gain sharper insights into the potential impacts on ecosystems and societies," Dr. Ziveri explains.
The study concludes that addressing these knowledge gaps is crucial for developing more accurate climate models that reflect the biological complexity of our oceans. This is a call to action for the scientific community to prioritize the study of these microscopic yet mighty organisms.
