Mangrove trees will influence the communities of soil Bacteria and Archaea byaffecting soil properties. Here, we tested the effect of two mangrove species(Rhizophora mangle and Avicennia germinans) on soil microbial communities at three locations in Florida, with a particular focus on ammonia oxidizers. Two of the sampling locations were tidal stations, while the other was impounded. Total bacterial and archaeal community compositions were assessed by MiSeq sequencing of 16S rRNA genes. Changes in the community compositions of ammonia-oxidizing bacteria (AOB) and archaea (AOA) were analyzed by 16S rRNA gene sequencing and Denaturing Gradient Gel Electrophoresis (DGGE) of amoA genes, and their abundance was established by quantitative PCR of amoA genes. In addition, we explored the influence of soil physico-chemical properties on microbial communities. Bacterial, archaeal, and ammonia oxidizers composition in soils associated with R. mangle and A. germinans differed only at the tidal stations. Hence, we concluded that tide may be required to maintain the differences in microbial communities between both mangrove species. Moreover, a correlation between soil salinity and OTU richness (? = -0.833, p < 0.05)suggested a strong influence of tides on structuring microbial communities. Since these conclusions are based on only two tidal and one non-tidal location, more of these locations should be analyzed to substantiate the role of tide in maintaining microbial community structures in the zones of mangrove trees. AOA were always more abundant than AOB, but the effect of mangrove species on total numbers of ammonia oxidizers was location-specific. AOB but not AOA abundances correlated negatively with several physicochemical variables, suggesting that AOB could be more easily influenced by the environmental factors measured, whereas AOA may be less sensitive to them and therefore became numerically dominant in this environment.