Resumo

Microbial communities play an important role in nutrient cycling and geochemical processes in soils and sediments. However, it is not known how the structure of microbial communities in soils of mangrove changes over time. Understanding the temporal and spatial patterns of diversity and distribution of communities is a key issue in ecology, given that this knowledge can help predict responses to impacts and guide conservation and/or restoration actions of impacted ecosystems. Aiming to monitor the microbial community structure of sediments in the vicinity of the roots of Rhizophora mangle from Pacoti mangrove (State of Ceará, NE Brazil) sediments were sampled during dry and wet seasons in 3 different sites along the river course over 5 years, and the structure of Bacteria and Archaea was monitored by DGGE for the 16S rRNA gene. Furthermore, we aimed to verify the correlation, by means of redundancy analysis (RDA), between the microbial community structure and the environmental variables (pH, salinity, organic matter and silt-clay contents) measured for each sample. Analyzing the clusters derived from the DGGE profiles for the communities of Bacteria and Archaea, we noticed that the sampling sites were grouped quite differently over the years. Analyzing the ribotype richness, i.e. the number of bands in the DGGE, it can be observed that for Bacteria, the number of bands in the gels ranged from 10 to 29, with site 3 (the farthest from the river mouth) presenting the lowest average richness. For Archaea, the number of bands ranged from 14 to 38, and also the lowest average richness over the 5 years of monitoring was observed in site 3. The RDA revealed that the silt-clay contents explained most of the variance along the majority of the years of monitoring for both Bacteria and Archaea. In this study, we observed a large variability in the structure of microbial communities over the five years and a part of the community structure can be related to the silt-clay contents in the sediments. Studies such as this restate the need of long-term researches intending to monitor soil microorganisms in mangroves, as these are key parts for conservation and resilience of such important ecosystems.