Diversity and composition of molecular biome profiles in Danish freshwater streams
Diversity and distribution of the obtained biome profiles was assessed using the estimated richness as calculated per domain by alpha diversity index Chao1 (Figure 1). The lowest average number of bacterial ZOTUs was observed in the samples from good ecological status (4,243 ± 1,414 ZOTUs) (Figure 1a), while the highest was seen in the samples of poor ecological status (5,790 ± 1,777 ZOTUs). No immediate relationship between the bacterial diversity and ecological status of the sampled locations was apparent (p > 0.05), and a similar pattern of diversity was observed for the Archaea ZOTUs. A trend towards increased diversity with better ecological status was observed for the Eukaryotic ZOTUs (Figure 1b), where an average 54 ± 3 ZOTUs were observed in the samples representing bad ecological quality, opposite 93 ± 25 ZOTUs in samples of high ecological status. However, statistical testing revealed no significant differences (p > 0.05) in the estimated number of ZOTUs across all 5 ecological status categories in all three domains. Bacterial and Eukaryotic ZOTUs had a relatively low variation between samples of the same groups, compared toArchaea , where a larger variation was observed.
The composition of the molecular biome profiles across ecological status categories was further examined per domain (Figure S2-S4). Prior to analysis, all ZOTUs associated to Chloroplasts were filtered from the dataset. The majority of the abundant bacterial community members were observed across all ecological status groups (Figure S2), including multiple representatives of Rhodoferax, Nitrospira, Comamonadaceae and Anaerolineaceae . Representatives of the genusBacillus , as well as one ZOTU representing Nitrospira were almost exclusively detected in samples representing good and high ecological quality. Representatives of the domain Archaea were detected sparsely in samples across all five ecological status categories (Figure S3). The majority of abundant archaeal ZOTUs were associated to the class Bathyarchaeia and the familyNitrososphaeraceae . For the Eukaryota , several abundant organisms were observed across all ecological status groups, including representatives of the insect order Diptera and the plant division Magnoliophyta (Figure S4). Other eukaryotic ZOTUs were more sparsely detected in the sampled locations, and included invertebrates, fungi and annelids. Representatives of the flatworm groupContinenticola were primarily observed in samples of good and high ecological status.