Estrutura e diversidade taxonômica e funcional das assembléias de archaea e bactéria associadas a sedimentos portuários da plataforma continental do Ceará (NE – Brasil)

Abstract

This research describes the structure, diversity and function of Bacteria and Archaea assemblages associated to sediments from two seaports in the Continental shelf of Ceará state and the evaluation of the effects of architectural and operational differences on those communities. Structure and richness of Archaea and Bacteria assemblages were studied by Denaturing Gradient Gel Electrophoresis (DDGE), using 10 samples obtained at Port of Pecém and 15 at Port of Mucuripe. After this preliminary evaluation, the samples were pooled and compared against an external pool from a region without seaport activities. The sediments also had its granulometry, carbonate, organic matter, nitrite, nitrate, sulfate, metals, biphenyls and polycyclic aromatic hydrocarbons (PAHs) contents analyzed. The DGGE profiles were compared based on Jaccard similarity index, richness estimators and measures of beta diversity. Finally, the taxonomic and functional diversities associated with the sediments were accessed by pyrosequencing of the metagenomes. The sediments differed in relation to its amounts of carbonate, organic matter, metals (Cu, Cr, Ni, Zn and Fe), nitrate, nitrite and sulfate, more concentrated in Port of Pecém, as well as total organic carbon, more concentrated in Port of Mucuripe. The structure of Archaea and Bacteria assemblages were different in both ports as well as the sampling stations in each port, with a more elevate richness found on Port of Mucuripe. Besides, beta diversity measures pointed Port of Mucuripe as a more heterogenic environment than Port of Pecém. The comparison of the pooled samples suggested the selection of peculiar operational taxonomic units in each port. The metagenomic analysis showed the prevalence of Deltaproteobacteria and Actinobacteria in Port of Pecém, and Cyanobacteria, Bacteroidetes and Chloroflexi in Port of Mucuripe, and that both ports did not differed functionally. In Port of Pecém, the dominance of Thaumarchaeota stand out. The peculiar taxonomic composition of Port of Mucuripe suggested that changes caused by the impacts accumulated in more than 50 years of operation lead to the selection of dominant taxa, Synechococcus, Rhodothermus and Sphaerobacter, which could be evaluated as potential bioindicators of chronically contaminated sediments from ports.