Thermal trait variation may buffer Southern Ocean phytoplankton from anthropogenic warming

Area of Science:

• Marine biology
• Climate change science
• Genetics

Background:

• Marine phytoplankton are crucial for ocean ecosystems and are sensitive to climate change.
• Southern Ocean surface waters are warming rapidly, yet phytoplankton responses to temperature are uncertain.
• Intraspecific trait variation is key for adaptation but poorly understood in phytoplankton.

Purpose of the Study:

• To investigate inter- and intra-specific thermal trait variation in Southern Ocean diatoms.
• To reduce uncertainty in predicting marine ecosystem responses to climate change.
• To assess the adaptive potential of phytoplankton to projected ocean warming.

Main Methods:

• Developed a high-throughput growth assay for simultaneous thermal performance analysis.
• Examined 43 diverse and important Southern Ocean diatom species.
• Analyzed growth responses across a range of temperatures.

Main Results:

• Significant differences in thermal traits (optimum and maximum growth temperatures) were observed among species.
• Intraspecific variation (among strains) showed coefficients of variation from 3% to 48%.
• Predicted biogeographic ranges varied by up to 97% based on strain-specific temperature tolerance.

Conclusions:

• Southern Ocean diatoms possess substantial thermal trait diversity.
• This genetic variation may allow phytoplankton communities to adapt to projected 21st-century warming.
• Strain-level differences are critical for accurate predictions of future phytoplankton biogeography.