Comparison of methods to measure acute metal and organometal toxicity to natural aquatic microbial communities

Abstract

Microbial communities in water from Baltimore Harbor and from the mainstem of Chesapeake Bay were examined for sensitivity to mercuric chloride, monomethyl mercury, stannic chloride, and tributyltin chloride. Acute toxicity was determined by measuring the effects of [3H]thymidine incorporation, [14C]glutamate incorporation and respiration, and viability as compared with those of controls. Minimum inhibitory concentrations were low for all metals (monomethyl mercury, <0.05 ,ug liter-1; mercuric chloride, <1 ,ug liter-1; tributyltin chloride, <5 ,ug liter-) except stannic chloride (5 mg liter-'). In some cases, mercuric chloride and monomethyl mercury were equally toxic at comparable concentrations. The Chesapeake Bay community appeared to be slightly more sensitive to metal stress than the Baltimore Harbor community, but this was not true for all treatments or assays. For culturable bacteria the opposite result was found. Thymidine incorporation and glutamate metabolism were much more sensitive indicators of metal toxicity than was viability. To our knowledge, this is the first use of the thymidine incorporation method for ecotoxicology studies. We found it the easiest and fastest of the three methods; it is at least equal in sensitivity to metabolic measurements, and it likely measures the effects on the greater portion of the natural community.

Biological and chemical aspects of differences in sensitivity of natural populations of aquatic bacterial communities exposed to copper

“…This notion is also needed for the Rhine Action Plan and the North Sea Action Plan, for which several metals, among them copper, are priority compounds. A previous study indicated that bacterial populations from the River Rhine responded very strongly to small additions of copper (Tubbing and Admiraal, 1991a), which tallies with observations in other waters (Vives Rego et al, 1986;Jonas et al, 1984). Although natural microbial populations may provide sensitive criteria for assessing effects on ecosystems, there are also a number of obstacles.…”

Sensitivity of Bacterioplankton in the Rhine River to Various Toxicants Measured by Thymidine Incorporation and Activity of Exoenzymes

“…['4C]Glucose turnover in pond water [20] and in river water [6] and amino acid turnover in estuarine waters [19] were as sensitive to the addition of 10 to 100 pg L-' copper as thymidine incorporation was in our study. Jonas et al [7] opined that thymidine incorporation should be a more universal parameter for testing acute toxicity of compounds than the activity specific to certain types of bacteria, e.g., sulfate reduction, because thymidine is so upiversally utilized by bacteria. Any interference of a toxicant with the cellular metabolism of heterotrophic bacteria would thus be detected.…”

“…Numerous studies have indicated that metabolic processes of microorganisms are very sensitive to pollutants [2,3] and hence the in situ activity of microbial communities has been used for establishing the effects of perturbations. The responses of aquatic bacteria to toxicants have been studied with various microbial techniques, including respiratory activity [4], acetate incorporation, glucosidase activity [ 5 ] , and, more recently, glucose metabolism [6], thymidine incorporation [7,8], and enzyme activity [9,10].…”

Metals and microbes in toxicity testing

“…These observations reinforce the conclusion that the chemical species of a metal is important. Jonas, et al (1984) used four methods to estimate minimum inhibitory concentrations (MIC) for natural bacterial populations from Chesapeake Bay exposed to mercury and tin compounds (Table VII). MIC values were at least ten times lower when measured using radiolabeled substrates as when measured by plate counts.…”