Hydrology Masks Warming Effects on Microbial Communities in Salt Marsh Soils

Soil microbial communities play a pivotal role in salt marsh ecosystem functioning, including organic matter decomposition and greenhouse gas cycling. It is currently unknown how climate warming will affect the diversity and activity of salt marsh soil microbial communities, hindering our ability anticipate the fate of the vast stores of soil organic carbon in these so-called Blue Carbon ecosystems. In this study, we therefore leveraged the Marsh Ecosystem Response to Increased Temperature (MERIT) experiment, to investigate the effect of experimental warming on the putatively active microbial community structure (rRNA transcripts) and the exo-enzymatic activity of both C- and N-acquiring enzymes. We show, that the putatively active microbial community structure remains stable after five years of experimental warming. Yet, we demonstrate that experimental warming promotes drought-tolerant phyla (Actinobacteriota, Firmicutes), these changes were associated with an increase potential for the degradation of relatively recalcitrant soil carbon compounds. Please note that this is not a classifical analysis on the DNA of the 16S rRNA gene. Instead the RNA as a measure for the active microbial community was extracted, and reverse transcribed to cDNA. Subsequently, 16S rRNA amplicon libraries were generated.