According to new computer model simulations, a metabolic hack makes phytoplankton more resilient to 21st century climate change than previously thought. Credit: Institute for Basic Science
Key Points:
- A study shows that marine phytoplankton are more resilient to future climate changes than once thought.
- Analysis of the upper ocean phytoplankton shows that productivity can be sustained, even in very nutrient-depleted conditions.
- Scientists can use future models to predict phytoplankton’s response to 21st century global warming.
An international team of scientists published a new study in Science Advances that provides evidence that marine phytoplankton are much more resilient to future climate change than previously thought.
The scientists combined data from the long-term Hawai'i Ocean Time-series program with new climate model simulations, to reveal that a mechanism known as nutrient uptake plasticity allows marine algae to adapt and cope with the nutrient-poor ocean conditions predicted over the next decade due to oceanic global warming.
The tiny algae known as Phytoplankton live near the ocean’s surface and are able to absorb nutrients and take up dissolved carbon dioxide and release oxygen, which makes up for about 50% of the oxygen that we breathe.
Earlier studies suggest that the future depletion of nutrients near the surface would lead to a substantial reduction of ocean’s phytoplankton production, but new upper ocean analyses of the phytoplankton shows that productivity can be sustained, even in very nutrient-depleted conditions.
“Under such conditions individual phytoplankton cells can substitute phosphorus with sulfur. On a community level, one might see further shifts towards taxa that require less phosphorus,” said David Karl, co-author of the study, professor in oceanography at the University of Hawaii.
The team ran a series of climate model simulations with the Community Earth System model to study how this unique metabolic “hack” will impact global ocean productivity over the next few decades. First, authors qualitatively reproduced previous model results of a decline in global productivity by turning off the phytoplankton plasticity in their model. Next, they turned on the plasticity parameter to capture the observations from the past three decades, which revealed an increase of up to 5 % in global productivity until the end of the 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.
“Models without plasticity tend to project overall declining primary production for the 21st century, whereas those that account for the capability of phytoplankton to adapt to low nutrient conditions show on average increasing global productivity,” said M.G. Sreeush, co-corresponding author of the study and a postdoctoral fellow at the IBS Center for Climate Physics.
The team says future Earth system models need to use improved observationally-based representations of how phytoplankton respond to multiple stressors, including warming and ocean acidification.