AME 80:29-41 (2017)  -  DOI: https://doi.org/10.3354/ame01837

ABSTRACT: Microbial communities play key roles in biogeochemical cycles across the planet and their composition and the factors that structure them are well documented. However, how changes in abiotic conditions can affect the active proportion of the microbial community that is responsible for the delivery of key ecosystem services is poorly understood. Salt marshes, in particular salt marsh ponds, are highly dynamic habitats with abiotic conditions in the pond water that fluctuate on daily cycles. To determine how diurnally driven changes in abiotic conditions affect active microbial communities, we sampled a single salt marsh pond every 4 h over 2 diel cycles, sampling 2 dynamically different habitats: the pond sediment and overlying water. We assessed abiotic conditions and the total and active microbial communities using high-throughput sequencing of the 16S rRNA gene and 16S rRNA. Sediments displayed no discernable pattern and low variation in abiotic conditions, leading to stable active microbial communities. However, the cyclical, rapidly changing abiotic conditions in the overlying water resulted in large changes in the active microbial community and in the percent of inactive taxa. Our data suggest that changes in environmental condition over short time periods alter the structure of active microbial communities. Further, our data show that the most abundant taxa in the active communities in the overlying water were rare (<1% total abundance), suggesting that under environmental change, rare taxa can disproportionally contribute to the activity of microbial communities.

KEY WORDS: Microbial activity · Dormancy · Rare biosphere · Salt marsh · Marsh pond