Archaeal communities in the sediments of three contrasting mangroves

Purpose: This study evaluates the presence and diversity of 16S rRNA (rrs) and amoA genes from archaea in three mangrove sediments under different stages of preservation (one pristine mangrove, one affected by anthropogenic activity, and another contaminated by an oil spill) in the state of São Paulo (Brazil). Materials and methods: A combination of DGGE, coupled with ordination analysis, and clone libraries of both targeted genes (rrs and amoA) was used to infer the diversity and phylogeny of archaeal communities in the mangrove analyzed samples. Results and discussion: The DGGE combined with multivariate analysis revealed, based on the ribosomal gene, differences in archaeal communities according to environmental parameters such as mangrove location, anthropogenic activity, and oil contamination. The profiles based on the amoA gene were more similar than those obtained for the gene rrs, with the only difference statistically observed for the community found in the mangrove under anthropogenic pressure. Furthermore, phylogenetic analysis revealed most archaeal groups affiliated to sequences belonging to the Thaumarchaeota (53. 1%, 24 OTUs) and Euryarchaeota (29. 6%, 14 OTUs) phyla, in addition to 14 sequences affiliated to an unclassified Archaea (16. 1%, 8 OTUs). Concerning the analysis of the amoA gene, mangroves harbored sequences affiliated with those previously described in water column and soil/sediment samples, besides two possible clusters specifically found in mangroves. Conclusions: The findings are that the mangroves act as a reservoir for archaeal diversity, are possibly involved in nitrogen transformation in this ecosystem, and are affected by distinct pressures caused by anthropogenic activities.