Ecologia microbiana de riachos influenciados pela exploração de petróleo no Brasil.

Abstract

Human activities can cause degradation of ecosystems and interfere with the availability of the environmental services they provide to society itself. Preventing degradation from happening is the best strategy to ensure the availability of these services, and for this to happen, human activities have to be constantly monitored. One of the most used monitoring strategies is the measurement of indicators that represent the homeostasis of the environment and have the sensitivity to identify the initial signs of degradation. In this study we characterize the microbial communities of continental aquatic environments in the Amazon, Atlantic Rainforest, Cerrado and Caatinga and use this data to select indicators of oil exploration activity impacts (oil fields operating for at least 25 years with no history of spills). We evaluated the taxonomic and functional diversity through 16S gene sequencing and GeoChip 5.0M functional gene microarray. Results from water, sediment, biofilm and stream banks soil samples influenced by oil fields were compared to minimally impacted reference areas. In addition to the microbial communities, we analyse physical-chemical parameters of water, inorganic parameters in water, soil and sediment and organic parameters (n-alkanes and polycyclic aromatic hydrocarbons) in water and sediment. All sampling stations showed microbial communities with high species richness and more than 80% functional genes detected with GeoChip. The microbial communities presented low taxonomic similarity, sharing less than 30% of the species with each other. On the other hand, they showed high functional similarity, sharing more than 70% of the genes. The main impact of the oil exploration activity was land use, as evidenced by the increase in the concentration of metallic ions, the electrical conductivity, the number of genes related to the metal homeostasis, the abundance of metal related oxidative stress response genes and the number of soil microbial species in the water of the streams influenced by the exploration activity. No evidence of hydrocarbon contamination was found at the sample stations evaluated. Several microbial species and functional genes were identified as promising indicators of oil exploration activity in streams but it was not possible to link these indicators to specific taxonomic groups nor to preferential metabolic activities. This points to a paradigm shift in the use of indicators for environmental monitoring, indicating that instead of indicator species or indicator functional groups, it will be more promising to develop a concept related to indicator genetic sequences.