Spatial patterns in bacterial community structure and function within shallow alpine tarns

Abstract

Small scale spatial variation in bacterial community structure and function in freshwater ecosystems is poorly understood. I investigated the spatial variation of bacterial communities within three tarns located at Tekapo Scientific Reserve using automated ribosomal intergenic spacer analysis (ARISA). I examined the variability in bacterial community structure both within and among tarn locations and explored whether bacterial communities adhere to the same biogeographical patterns commonly reported for communities of larger organisms; these were the taxa-area and distance-decay relationships. I also attempted to identify physicochemical variables that were significantly related to the observed community heterogeneity. To achieve these aims, I collected more than 100 samples in total across the three tarns and measured a range of physicochemical variables (pH, conductivity, total carbon and anion concentrations) for each sample. The ARISA data revealed significant variability in bacterial community structure among the tarns and some variation within the tarns that was related to correlated spatial variability in a range of physicochemical variables such as, pH, total carbon and conductivity. Distance-decay and taxa-area relationships in bacterial community similarity were also observed. There was no correlation between the structural and functional attributes (i.e., carbon substrate utilisation patterns) of the bacterial communities, suggesting that there was some functional redundancy in these bacterial communities in terms of carbon substrate utilisation. This study provides valuable information about how freshwater bacterial biodiversity is maintained and expands our understanding of the link between bacterial community structure and function.