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Water Availability and Air Humidity Strongly Affect Photosynthesis in Biofilms on Tree Trunks: Predictions for a
Ana Beatriz de Lima Freitas1, Tiago Vilas-Boas1,2, Cleber Cunha Figueredo1
1Departamento de Botânica, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
Environmental Microbiology
|July 25, 2026
Summary
Epiphytic cyanobacterial biofilms rapidly recover photosynthesis after rehydration, but require significant water availability for full function. Increasing drought frequency due to climate change threatens these vital organisms.
Area of Science:
- Environmental Microbiology
- Plant Physiology
- Climate Change Science
Background:
- Epiphytic cyanobacterial biofilms play crucial roles in ecosystems.
- Climate change is increasing drought frequency globally.
- Understanding factors affecting biofilm photosynthesis is vital for predicting ecosystem responses.
Purpose of the Study:
- To investigate the impact of water availability and air humidity on the photosynthesis of epiphytic cyanobacterial biofilms.
- To assess the recovery rates of photosynthetic parameters after rehydration.
- To analyze long-term climate trends and their implications for biofilm survival.
Main Methods:
- Field measurements and controlled laboratory experiments involving hydration-dehydration cycles.
- Chlorophyll fluorescence measurements: potential quantum yield (Fv/Fm), relative electron transport rate (rETRmax), and photosynthetic photon flux density at saturation (PPFDsat).
- Analysis of historical precipitation and relative humidity data (1961-2024).
Main Results:
- Biofilms were inactive when dry (Fv/Fm=0) but recovered rapidly (Fv/Fm≈0.5) within 2 hours of rehydration.
- 50% Fv/Fm recovery required ~16% bark water content; full recovery of rETRmax and PPFDsat needed >30% water.
- Photosynthetic reactivation depends on liquid water, while air humidity affects water availability duration.
Conclusions:
- Epiphytic cyanobacterial biofilms are highly vulnerable to water stress caused by increasing drought.
- Climate change-induced drying trends pose a significant threat to the ecological function of these biofilms.
- These findings underscore the need to consider the impact of climate change on epiphytic communities and ecosystem services.
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