Longitudinal sampling from rainwater tanks throughout Australia was employed to analyse the microbial ecosystems in water supplies. Epidemiological research indicates that drinking rainwater does not create averse health impacts. The concept that domestic rainwater storage tanks may host sustainable microbial ecosystems that improve water quality has not previously been addressed. The bacterial diversity, cultivated from more than 80 samples from 22 tanks at various locations across eastern Australia, is presented as evidence of potential operation of a functional micro-ecology within rainwater storage systems. In combination with low abundance of bacteria associated with faecal contamination, the results indicate high quality water and beneficial ecosystem processes. A recent presentation to the RHAA on water quality processes in rainwater harvesting systems is also provided.
Cultivated isolates were found to comprise members of four major bacterial divisions; Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes, including more than 200 species from 80 different genera. The pattern of abundance distribution was typical of that observed in most natural communities, comprising a small number of abundant taxa and a multitude of rare taxa, while the speciﬁc composition resembled that previously described in a number of natural aquatic systems. Although Proteobacteria from α, β and γ sub-classes were dominant, a set of core taxa comprising representative genera from all four phyla could be identiﬁed. Coliform and other species speciﬁcally associated with faecal material comprised < 15% of the species identiﬁed, and represented < 1.5% of total average abundance. The composition of the cultivated populations and scope of diversity present, suggested that rainwater tanks may support functional ecosystems comprising complex communities of environmental bacteria, which may have beneﬁcial implications for the quality of harvested rainwater.