Cyanobacteria in semi-arid inland floodplain wetlands

Microbial communities provide vital metabolic processes in semi-arid inland floodplain wetlands. We used high-throughput sequencing to investigate the composition and relative abundance of soil bacterial communities in the Macquarie Marshes of south-east Australia, targeting bacterial 16S rRNA gene. Dry soil samples were collected from 50 locations at sites in two wetlands (25 samples from each wetland) with different geochemical properties and past inundation frequency. All samples were inundated in the laboratory. Of the bacterial communities recovered from the inundated soil samples, cyanobacteria formed a minor component, relative to other bacterial phyla like Actinobacteria and Proteobacteria. The spatial distribution of Actinobacteria showed a significant negative relation, and Proteobacteria showed a significant positive relation, with the past inundation frequency. However, there was no significant relation between the spatial distribution of cyanobacteria (dominated by Nostocophycideae) and the past inundation frequency. Cyanobacteria seem to occupy a different hydro-ecological niche from other major components of the bacterial communities in these semi-arid inland floodplain wetlands. Further analysis of cyanobacterial spatial dispersion with other environmental gradients should be considered to explain their spatial occurrence in those environments.