Dehydrogenase activity of soil microflora: significance in ecotoxicological tests
1991
Rossel, D. | Tarradellas, J.
The dehydrogenase activity (DHA) of the microflora of a gleyic luvisol artificially contaminated by 1, 10, and 100 microgram tributylin (TBT)/g dry wt soil was compared with its ATP content, long-term CO2 evolution, and esterase activity. DHA was measured by reduction of triphenyltetrazolium chloride. This 203-day laboratory experiment comprised a phase of air drying, a remoistening, and the addition of a substrate (alfalfa and yeast extract). The half-life of TBT ranged from 40 (10 and 100 microgram/g) up to 70 days (1 microgram/g). The microflora was not affected by 1 and 10 microgram TBT/g. After an initial 60% stimulation, the respiration and esterase activity in the soil contaminated by 100 microgram/g TBT/g recovered to the level of the control soil in 2 and 14 days, respectively. About 50% depression of DHA and ATP content was observed throughout the 203 days of the experiment. DHA inhibition was correlated with depression of ATP content (r = 0.82). Air drying, remoistening, and substrate addition had little influence on the depression of DHA and of the ATP content. Unlike long-term CO2 evolution, DHA did not reflect the total effective activity of soil microflora; rather, it reflected its total potential activity. As for biomass estimates using substrate-induced respiration, a clear distinction should be made between short-term DHA and other measurements of DHA. Short-term DHA, as a substrate-induced maximum initial activity, appears mainly to reflect the biomass of soil microflora. The measurement of DHA appears to be a suitable low-cost and sensitive tool for assessing side effects of chemicals.
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