Short-Time Effect of Heavy Metals Stress on Key Enzyme Indicators in River Sediments

Y. TODOROVA and Y. TOPALOVA
Sofia University “St. Kliment Ohridski”, Faculty of Biology, Department of General and Applied Hydrobiology, BG – 1164 Sofia, Bulgaria

Abstract

Todorova, Y.  and Y. Topalova, 2013. Short-time effect of heavy metals stress on key enzyme indicators in river sediments. Bulg. J. Agric. Sci., Supplement 2, 19: 282–285

 

The pollution of aquatic ecosystems made the necessity of new technologies for environmental decontamination more urgent. Bioremediation approaches involving microbial degradative capacities are regarded as effective and environmental friendly alternatives. As mediators in key biodegradation processes, the complex enzyme activities (measured as a total of extracellular and intracellular activity on organism and sub-organism level) have the potential to be used as indicators for mechanisms and rate of transformation processes. However, the presence of some toxic and xenobiotic substrates can modulate (activate or inhibit) the enzyme activities and affects the degree of pollutants transformation. The main objective of this study was to assess the effect of heavy metals on key enzyme indicators (total dehydrogenase activity – DHA and phosphatase activity index – PAI) in sediments of Iskar River middle part. The inoculation with moderate concentrations of cadmium stimulated the DHA but the further increasing inhibited the activity with 80%. The Cu2+ had a specific effect by the location of sediments. The Pb2+ and Zn2+ in all used concentrations inhibit the DHA with 35–95%. The PAI was inhibited by all tested heavy metals but the Zn2+-ions have the higher impact (over 75% inhibition).

Key words: enzyme indicators; Total Dehydrogenase Activity, Phosphatase Activity Index, heavy metal stress, river sediments
Abbreviations: DHA – total dehydrogenase activity; PAI – phosphatase activity index; MHPPs – micro-hydro power plants; HMs – heavy metals

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