Xenobiotics’ impact on black sea prokaryotic communities’ qualitative composition

Abstract

Abstract. Biotransformation and bioremediation mediated by microbial communities is known to determine the fate of pollutants in the ecosystems and their effect on other biota preventing from xenobiotics accumulation in the food web. These processes are even more important in semi-closed marine ecosystems, which receive plenty of river run-off, such as the Black Sea. An ubiquity of polyaromatic hydrocarbons and organochlorine compounds, are present in the Black Sea water in concentrations, which exceeded maximum permissible, according to the results of the Joint Black Sea Surveys 2016 conducted in the course of UNDP EMBLAS project.  In addition, the presence of pesticides, herbicides and pharmaceutical products was detected at the majority of monitoring stations. Therefore, it is expedient to assess microbial communities’ taxonomic and functional diversity with the emphasis on xenobiotics’ biotransformation potential, in order to analyze the Black Sea ecosystem functional response towards constant pollution inflow. Such research has the potential to contribute to the estimation of Marine Framework Strategy Directive indicators and to Black Sea ecological status assessment. Black Sea microbial taxonomic diversity was assessed in seawater and sediments samples collected during Joint Open Sea Survey conducted in the course of UNDP EMBLAS-II project. Genomic DNA was extracted from the samples and 16S V3 was sequenced at Ion Proton platform. Consequently, prokaryotic taxonomic diversity was determined with QIIME-II pipeline using Green Genes and SILVA databases. Our data indicates the presence of a number of taxonomic groups, known to be responsible for organic pollutants’ degradation. Such taxa, as Rhodobacteraceae, Rhodospirillaceae, Halomonadaceae Oceanospirillaceae, Alcanivoracaceae, Bacilliaceae, Actinomycetales and Acidobacteriaceae were detected in Black Sea water at the majority of the stations. Sediments samples were characterized by overall higher bacterial diversity and harbored Alteromonadales and Piscirickettsiaceae, which have experimentally proven polyaromatic hydrocarbon degradation capability. Besides, Desulfuromonadaceae, Desulfobacteraceae, Syntrophaceae, Peptococcaceae and Dehalococcoideaceae, previously shown to act in organochlorine compounds biotransformation, comprised a significant portion of sediments microbial community. The results obtained are the baseline for subsequent detailed studies of Black Sea microbial communities functional biodegradation potential. This, in turn, sets the background for the research of ecosystem adaptation strategies to anthropogenic xenobiotic pollution and to the identification of novel metabolic pathways involved in this process.