Acute Copper and Cupric Ion Toxicity in an Estuarine Microbial Community

Abstract

Copper was acutely toxic to the estuarine microbial community of Middle Marshes, N.C. Under ambient water quality conditions, 10 ,ug of added total copper [Cu(II)] liter-' reduced the CFU bacterial abundance by up to 60% and inhibited the amino acid turnover rate (AATR) by as much as 30%. Copper toxicity, however, was a quantitative function of free cupric ion (Cu2+) activity that was not directly related to Cu(II) or ligand-bound copper. By using a nitrilotriacetic acid-cupric ion buffer to control pCu (-log Cu2' activity), it was found that an in situ pCu of 10.1 was bactericidal, reducing the CFU by 60%, but inhibited the AATR by only about 10%. A bacterial bioassay that was used to estimate the pCu in Cu(II)-treated Middle Marshes samples indicated that less than 0.5% of added Cu(II) was in the free cupric ion form. CFU was a more sensitive indicator of low-level copper stress than was AATR. When tested at different times, native microbial community responses to acute cupric ion stress were quantitatively quite similar even when there were large differences in bacterial abundances and in situ metabolic rates. Variations were observed in response to Cu(II) treatments at different times, but these were likely due to differences in water quality, which would quantitatively influence the distribution of copper complexes that were present. Asymptotic response curves suggest that some degree of copper resistance exists in this community. At a pCu of 8, more than 2 orders of magnitude above the minimum inhibitory level, the CFU was still 5 to 10% and the AATR was about 3% of the control values.

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

“…However, thymidine incorporation in aerobic and anaerobic slurries of marine sediments was slightly more sensitive to organic aromatic pollutants than uptake of ['4C]glucose [8]. ['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.…”

The effects of copper on the microbial community of a coral reef sponge

“…This mechanism may extend to a protective role against toxicants for the host sponge. Jonas (1989) demonstrated that free Cu 21 and not total or ligand-bound copper was responsible for toxicity to an estuarine bacterial community. In our experiments, the density of total culturable bacteria was reduced significantly at and above 1.7 mg l 21 Cu 21 after 14 days (Fig.…”

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

“…These observations agreed with those of Banoub (19841, who found that organic matter considerably reduced the toxicity of copper to bacterial populations in the Rivers Rhine and Neckar and in sewage sludge. Similarly, Zevenhuizen (1979) and Jonas (1989) showed that additions of complexing substances alleviated the free Cu-ion concentration to a tolerable level for the growth of surviving bacteria. In this study, it was hypothesized whether or not increased community tolerance had been induced in the moderately copper-exposed waters in the tests.…”