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Effects of chlorinated hydrocarbons on the heterotrophic activity of aquatic microorganisms

University of British Columbia

This study investigated the short-term inhibitory effects of 8 chlorinated compounds on aquatic microorganism heterotrophic activity. A technique involving the measurement of substrate uptake rates using radio-actively labeled glucose was employed. All compounds studied have been identified as foreign pollutants in aquatic environments and include the highly toxic ones DDT, dieldrin and a PCB (Aroclor 1254). The aquatic microorganisms were predominatly bacteria. On a short-term basis, the PCB and tetrachlorophenol were the most toxic pollutants, decreasing the maximum glucose uptake rate (Vmax) by 50 percent at 250 ppb concentrations. The remaining pollutants had little effect under 2500 ppb. In addition, tetrachlorophenol was the only compound to significantly increase glucose turnover time (Tt). Results from other experiments were: the toxicity of tetrachlorophenol varied according to the (environmental) water temperature; tetrachlorophenol affected the uptake of glucose more than that of two amino acids, alanine and glutamic acid; with respect to di-, tri-, and tetrachlorophenol, neither the chlorine percentage per pollutant molecule, nor the number of pollutant molecules per mole of water, varied linearly with the pollutant's ability to inhibit glucose uptake; the combined toxicities of various pollutants reduced uptake to only 9 percent below the average of their separate effects; and none of the 4 pollutants tested for long-term effects (DDT, PCB, dieldrin and tetrachorophenol) inhibited uptake after 4 days. It was concluded that the two tests (Type I and Type II as described in Section 2) were quick and reliable techniques for assessing the short and long-term effects of a concentration of a pollutant on heterotrophic activity. It was also determined that other pollutants should be tested for their long-term effects under a variety of conditions (for example, their effects on different substrates and on the sediment microbial community).

Text

2010-02-23

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http://hdl.handle.net/2429/20750

Zoology

University of British Columbia

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