Changes in the soil diatom community induced by experimental CO2 leakage

The role of soil biotic communities has received increasing attention in relation to global climate change management and, particularly, greenhouse gas dynamics. Soil CO2 fluxes are regulated by several physical, chemical and biological properties, and diatoms constitute a relevant component of the soil microbiological community. This study tests experimentally the effect of CO2 leakages and soil texture on soil diatom communities. Our results show profound changes associated to both factors, namely an increase in species richness in CO2-added treatments containing sandy-loam soils, and a segregation of diatom assemblages according to CO2 fluxes, irrespective of soil typology, as revealed by multivariate analysis. These effects seem to result from changes in soil pH since communities growing on alkaline plots show higher abundances but lower taxa numbers. No differences were found, however, when the two CO2 fluxes tested were compared. Finally, soil texture is revealed as an important factor explaining structural differences in the observed diatom assemblages. The findings described here may help to develop accurate CO2 leakage surveillance methods for geological storage sites.