Temperature variability interacts with mean temperature to influence the predictability of microbial phenotypes.

Area of Science:

• Marine microbiology
• Climate change biology
• Eukaryotic ecophysiology

Background:

• Tropical taxa may be vulnerable to rising temperatures due to stable environments near their thermal optima.
• Understanding responses to temperature variation is crucial for predicting microbial community shifts.

Purpose of the Study:

• To investigate how microbial eukaryotes with different thermal histories respond to temperature fluctuations.
• To assess the impact of temperature variability on growth, carbon fixation, and molecular responses.

Main Methods:

• Selected dinoflagellates with distinct thermal traits (tropical/temperate Coolia, Amphidinium strains).
• Exposed cultures to temperature fluctuations (±2, ±4°C) around sub- and supra-optimal means.
• Analyzed population growth, carbon fixation, cell volume, and molecular markers (gene expression).

Main Results:

• All strains showed reduced growth under fluctuations; narrower niche breadth strains had greater reductions.
• Suboptimal temperatures led to cell cycle arrest, reduced carbon fixation, and enlarged cell volumes.
• Supra-optimal temperatures induced novel trait combinations, increased phenotypic diversity, and divergent molecular responses (heat-shock proteins vs. energy pathways).

Conclusions:

• Temporal temperature variability interacts with thermal means to mediate microbial responses to climate change.
• Divergent physiological and molecular strategies observed between taxa highlight varied vulnerabilities and adaptations.
• Findings have implications for understanding future biogeochemical cycling in changing oceans.