Bacteria increase arid-land soil surface temperature through the production of sunscreens.

Estelle Couradeau,Ferran Garcia-Pichel,Ulas Karaoz,Ulisses Nunes Da Rocha,Hsiao Chien Lim,Eoin Brodie,Trent Northen

doi:10.1038/ncomms10373

Abstract

Soil surface temperature, an important driver of terrestrial biogeochemical processes, depends strongly on soil albedo, which can be significantly modified by factors such as plant cover. In sparsely vegetated lands, the soil surface can be colonized by photosynthetic microbes that build biocrust communities. Here we use concurrent physical, biochemical and microbiological analyses to show that mature biocrusts can increase surface soil temperature by as much as 10 °C through the accumulation of large quantities of a secondary metabolite, the microbial sunscreen scytonemin, produced by a group of late-successional cyanobacteria. Scytonemin accumulation decreases soil albedo significantly. Such localized warming has apparent and immediate consequences for the soil microbiome, inducing the replacement of thermosensitive bacterial species with more thermotolerant forms. These results reveal that not only vegetation but also microorganisms are a factor in modifying terrestrial albedo, potentially impacting biosphere feedbacks on past and future climate, and call for a direct assessment of such effects at larger scales.

Highlights

Soil surface temperature, an important driver of terrestrial biogeochemical processes, depends strongly on soil albedo, which can be significantly modified by factors such as plant cover
Surface soil temperatures are a function of the downwelling electromagnetic radiation and of the albedo of the soil surface[1]
Biocrusts can reduce the albedo of the soils they cover[11], and in some instances their development has been linked to concurrent increases in soil surface temperature[12,13,14]

Summary

Introduction

An important driver of terrestrial biogeochemical processes, depends strongly on soil albedo, which can be significantly modified by factors such as plant cover. We found that some cyanobacteria warm the soil surface by as much as 10 °C through the production of scytonemin, an alkaloid sunscreen pigment that strongly absorbs solar radiation and dissipates this energy as heat.

Results

Conclusion