Metabolic Hack Makes Ocean Algae more Resilient to 21st Century Climate Change
Published:26 Dec.2022    Source:ScienceDaily
A study published in Science Advances by an international team of scientists provides clear evidence that marine phytoplankton are much more resilient to future climate change than previously thought.Combining data from the long-term Hawai'i Ocean Time-series program with new climate model simulations conducted on one of South Korea's fastest supercomputers, the scientists revealed that a mechanism, known as nutrient uptake plasticity, allows marine algae to adapt and cope with nutrient-poor ocean conditions expected to occur over the next decades in response to global warming of the upper ocean.
The latest report of the Intergovernmental Panel on Climate Change (IPCC) states an uncertainty of -20% to +20%, which implies an uncertainty as to whether phytoplankton will increase or decrease in future. And global warming affects the upper layers of the ocean more than the deeper layers. Earlier studies suggested that the expected future depletion of nutrients near the surface would lead to a substantial reduction of ocean's phytoplankton production with widespread and potentially catastrophic effects on both marine ecosystems and climate. To study how this unique metabolic "hack" will impact global ocean productivity over the next few decades, the team ran a series of climate model simulations with the Community Earth System model (version 2, CESM2) on their supercomputer Aleph. By turning off the phytoplankton plasticity in their model, the authors were able to qualitatively reproduce previous model results of a decline in global productivity by about 8%. However, when turning on the plasticity parameter in their model, in a way that captures the observations near Hawai'i for the past 3 decades, the computer simulation reveals an increase in global productivity of up to 5% until the end of this century.  Inspired by the results of their sensitivity computer model simulations, the authors then looked at 10 other climate models, whose data were used in the recent 6th Assessment Report of the IPCC. The results confirmed the author's initial conclusions.

Even though our study demonstrates the importance of biological buffering of global-scale ecological changes, this does not imply that phytoplankton are immune to human induced climate change. For instance, worsening ocean acidification will reduce the calcification rates of certain types of phytoplankton, which can lead to large-scale shifts in ecosystems. These factors are neither well understood nor represented yet in climate models. Future Earth system models need to use improved observationally-based representations of how phytoplankton respond to multiple stressors, including warming and ocean acidification. This is necessary to predict the future of marine life on our planet.