Linking biosurface reactivity and photosynthesis to investigate Sphagnum mosses as ecosystem engineers.

Sphagnum mosses regulate peatland carbon storage, hydrology, nutrient cycling, and ecosystem functioning. However, the links among their surface chemistry, photosynthesis, responses to submersion and pH remain poorly understood. We quantified surface-chemical properties and biosorption potential in 20 field-collected species and four axenically cultivated conspecific clones. We measured gas exchange and Chl fluorescence in five representative species under submerged conditions across pH gradients. All Sphagnum species shared basic surface-chemical characteristics but differed in surface charge and abundance of reactive sites involved in proton and gas exchange, with generally higher biosorption potential in the Acutifolia and Sphagnum subgenera. Photosynthesis was maintained under waterlogging, although it varied among species and pH conditions. Reactive surface groups enhanced CO2 assimilation. Sphagnum palustre showed the broadest physiological tolerance, maintaining stable photosynthesis and photoprotection across all pH levels. In vitro cultivation reduced chemical variability among species but preserved the main surface-chemical properties. These results demonstrate that surface chemistry contributes to species-specific photosynthetic responses and ecological strategies under variable environmental conditions, while supporting the use of Sphagnum clones as standardized models for physiological research and environmental applications.