Petroleum effects on soil microbial communities
Crude oil is still the dominant energy source in Brazil where oil consumption keeps rising since 2013, reaching nowadays 2.2% of the world‟s energy consumption. A recent discovery of crude oil reservoirs at the Espirito Santo, Campos and Santos basins, can represent an excellent opportunity to meet the country‟s economic and energetic demands. However, offshore exploration offers risks to the microbiota and the whole sea life. Microbes are responsible for nutrient cycling can degrade recalcitrant organic compounds and several species have been reported as sensitive to petroleum hydrocarbons. This work aimed to evaluate microbial community shifts in soils under crude oil contamination and assess the effects of Biodiesel co-product (BCP) as a protecting agent of soil microbiota under crude oil addition. We used soils from the Trindade Island and from the Highfield research station at Rothamsted Research, UK. We assembled microcosms of 20 grams and contaminated the soils using weathered crude oil. Soils were incubated at 26° C with moisture correction to ca. 60% water holding capacity. We used CO2 evolution measurements to evaluate soil activity, during the incubation, and soil genomic DNA extraction, at the end of incubation period, to evaluate microbial community changes from treatments and controls. DNA was submitted to amplicon sequencing of 16S rDNA for Bacteria and Archaea and the ITS1 region for Fungi using Illumina MiSeq platform. We compared alpha and beta-diversity and taxonomic shifts. This thesis is divided in two chapters. The first describes the effects of crude oil on Trindade Island‟s soil microbial communities. In the second chapter we tested the protective effects of BCP on Trindade Island, Rothamsted‟s Bare Fallow and Grassland soils, against the amendment with crude oil. Crude oil had a major negative effect on microbial diversity for Trindade Island, but didn‟t change the diversity of Rothamsted agricultural soils. Taxonomy comparisons showed rise of the Actinobacteria phylum, shifts in several Proteobacteria classes and reduction of the Archaea class Nitrososphaerales. This is the first effort in acquiring knowledge concerning the effect of crude oil contamination in soils of a Brazilian oceanic island. This information is important to guide any future bioremediation strategy that can be required.
Micro-organismos, Bactérias, Solos - Contaminação, Hidrocarbonetos
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