Relationship between total heavy metal soil contamination and functional characteristics of microbial communities in urban soils of Bishkek
Ch. B. AIDYRALIEVA1, M. V. GORLENKO2, B. M. KHUDAIBERGENOVA3, S. A. KULACHKOVA2, V. A. TEREKHOVA2
1International Higher School of Medicine, Bishkek, Kyrgyzstan
2Lomonosov Moscow State University, Moscow, Russia
3National Academy of Sciences of the Kyrgyz Republic, Bishkek, Kyrgyzstan
Keywords: ecological assessment, bioindication, microbiome, soil respiration, functional diversity, multisubstrate testing, Saet index, soil health
Abstract
This study evaluates the relationship between soil chemical contamination and the state of the microbiome in urban soils from transportation, transport-industrial, and recreational zones of Bishkek city, as well as the Ala - Archa Nature Park. Total concentrations of Pb, As, Zn, Cu, Co, Mn, Cr, Cd, Hg, and Sb were determined in soils using a DELTA X - ray fluorescence spectrometer. It was shown that the degree of heavy metal contamination depended on traffic intensity and emissions from thermal power plants. Functional diversity of soil microbiomes was assessed via multisubstrate testing, and functional activity was measured by carbon dioxide emission using chromatographic methods. Microbial community health and stability were evaluated by the shape coefficient (d) of the rank distribution of substrate utilization spectra, serving as a measure of microbial system destabilization. A distinct microbial community state was observed in soils from the western part of the city, characterized by reduced substrate utilization, decreased metabolic activity, and community destabilization. The studied heavy metals were grouped according to their influence on biotic indicators such as microbial respiration and substrate consumption. The As - Pb - Cu - Co group was more strongly associated with the integrated heavy metal contamination index (Zst) and most strongly inhibited substrate-induced respiration and consumption of pentose monosaccharides. The Hg - Cr - Mn group mainly suppressed amino acid and organic acid consumption. The Cd - Zn - Sb group reduced basal respiration intensity and slightly increased oligosaccharide consumption and entropy parameters (Hk and χ2) of substrate utilization spectra. It was found that contamination with the ten studied heavy metals did not exert a direct specific effect on the microbiome, as the overall heavy metal contamination index (Zst) showed no significant correlations with any biotic indicators. The conclusion was made that only the combined consideration of abiotic (chemical contamination) and biotic (microbiome responses) criteria should be used to assess ecological risks of soil degradation.
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