## 4 Discussion
### Microbial Communities' Characterization  
Alpha diversity analysis showed that the alkylphenol compounds (NP and OP) did not significantly impact the microbial community, whereas the presence of PCP leaded to a decrease of the microbial diversity in CWs substrate at the end of the experiment. The impact of PCP in microbial diversity has been already observed in compost bacterial community [82], in aerobic granular sludge doped with PCP [83] and in soil acclimated with PCP [84]. In addition, [PERSON] et al. [85] observed that the microbial community of a mangrove soil was greatly influenced by PCP, with the preferential growth of bacterial groups that were active during PCP transformation, which might inhibit and compete with other bacteria for the limited living space and resources. Therefore, CWs microbial communities adapted to the presence of the contaminants, probably selecting the communities with capability to resist and degrade the compounds, leading also to the compounds biodegradation observed in CWs systems. However, microbial community structure showed that there was also an adaptation of the microbial community to the CW system conditions and not only to the presence of each contaminant. In both experiments, the \"initial\" microbial community (in T0) was different of the microbial community at the end of the experiment (in T8) independently of the exposure to non-doped or doped stream water. Over time, a natural species selection in the microbial community of each CW microcosms was observed, showing an adaptation to the experimental conditions. In the current study, the following bacterial phyla with abundance above 1% in CW substrate were detected: _Acidobacteria_, _Actinobacteria_, _Bacteroidetes_, _Dependentiae_, _Chloroflexi_, _Cyanobacteria_, _Firmicutes_, _Gemmatimonadetes_, _Thaumarchea_, _Nitrospirae_, _Planctomycetes_, _Proteobacteria and _Verrucomicrobia_. With the exception of the phylum _Dependentiae_ that was identified only in microbial community of experiment#2 (exposure to PCP), the remaining bacterial phyla were identified in CWs substrate from both experiments. A similar bacterial community with capacity to degraded NP was detected in river sediment: _Acidobacteria_, _Actinobacteria_, _Actinobacteria_, _Cyanobacteria_, _Firmicutes_, _Gemmatimonadetes_, _Nitrospirae_, _Planctomycetes_, _Proteobacteria and _Verrucomicrobia_[86]. Most of the phyla identified in this study have been discussed in the literature on their contribution in CWs treating wastewater, e.g., [87; 88; 89; 90] and on their contribution to the biodegradation or biotransformation of different types of emerging contaminants [87; 91; 92]. Plant species-specificity, with similar rhizobacterial communities, can be found in different environments where the same plant is present [93; 94]. For instance, [PERSON] et al. [95] have studied the microbial community of the same plant used in this study (_P. australis_) but retrieved from substrate samples of the CWs treating industrial wastewater and reported several phyla similar to those observed in this work, such as _Proteobacteria_, _Bacteroidetes_, _Firmicutes_ and _Actinobacteria_. The microbial degradation is reported to be the more important process by which organic compounds are biodegraded/biotransformed into less toxic, persistent and complex metabolites [96]. In this study, the _Proteobacteria_, _Bacteroidetes_ and _Planctomycetes_ were the three more abundant phyla in both experiments with relative abundance 58-72%. Due to their diversity and marked adaptability, these dominant phyla are able to degrade a variety of environmental organic contaminants, and also dominate the microbial community of the CW rhizosphere in wastewater treatment, e.g., [87; 89; 90].