Reply to comment of Kidron et al. (2025) on Büdel et al. (2008).

Abstract

In their recent paper Kidron et al. (Journal of Phycology, 2025) aimed to demonstrate that the reported extreme differences of up to 25°C between air and rock temperatures measured by Büdel et al. (Journal of Phycology, 2008) at Mt. Falconer in the Antarctic Taylor Valley, were likely in error. They suggested possible sources of errors that might have led to our modeling of dewfall. By reprogramming our (Hoffmann, 1955) and their (Beysens, 2018) suggested models, we have shown that our calculations regarding climatic data were correct, even with both models. We have provided new climate data from Linnaeus Terrace (Dry Valleys, Antarctica) to support our results, by water-related net photosynthesis of a unicellular (Chroococidiopsis sp.) and a filamentous cyanobacterial strain (Funiculus sociatus). In contrast to the claim of Kidron et al., both cyanobacteria showed positive net photosynthesis well below 1 mm precipitation equivalent water content. We suggest further improved field measurements to strengthen our observation and conclude that reactivation of inactive endolithic cyanobacteria by condensation could be possible but might not be the main source of water.