Development and field validation of a biotic ligand model predicting chronic copper toxicity to Daphnia magna

In this study, we developed a toxicity model predicting the long-term effects of copper on the reproduction of the cladoceran Daphnia magna that is based on previously reported toxicity tests in 35 exposure media with different water chemistries. First, it was demonstrated that the acute copper biotic ligand model (BLM) for D. magna could not serve as a reliable basis for predicting chronic copper toxicity. Consequently, BLM constants for chronic exposures were derived by multiple regression analysis of 21-d median effective concentrations (EC50s; expressed as Cu2+ activity) versus physicochemistry from a large toxicity dataset and the results of an additional experiment in which the individual effect of sodium on copper toxicity was investigated. The effect of sodium on chronic toxicity (log K NaBL = 2.91) seemed to be similar to its effect on acute toxicity (log K NaBL = 3.19). However, in contrast to the acute BLM, no significant calcium, magnesium, or combined competition effect was observed, and an increase in proton competition and bioavailability of CuOH+ and CuCO3 complexes was noted. Some indirect evidence was also found for some limited toxicity of complexes of copper with two of three tested types of dissolved organic matter. Because the latter was only a minor effect, this factor was not included in the chronic Cu BLM. The newly developed model performed well in predicting 21-d EC50s and no-observed-effect concentrations in natural water samples: 79% of the toxicity threshold values were predicted within a factor of two of the observed values. It is clear, however, that more research is needed to provide information on the exact mechanisms that have resulted in different BLM constants for chronic exposures (as opposed to acute exposures). It is suggested that the developed model can contribute to the improvement of risk assessment procedures of copper by incorporating bioavailability of copper in these regulatory exercises.

[1]  E. Tipping,et al.  A unifying model of cation binding by humic substances , 1992 .

[2]  B.-P. Elendt,et al.  Trace nutrient deficiency in Daphnia magna cultured in standard medium for toxicity testing. Effects of the optimization of culture conditions on life history parameters of D. magna , 1990 .

[3]  Colin R. Janssen,et al.  The biotic ligand model: a historical overview. , 2002, Comparative biochemistry and physiology. Toxicology & pharmacology : CBP.

[4]  S. Tao,et al.  Bioavailability of Apparent Fulvic Acid Complexed Copper to Fish Gills , 2000, Bulletin of environmental contamination and toxicology.

[5]  P. Paquin,et al.  Biotic ligand model of the acute toxicity of metals. 2. Application to acute copper toxicity in freshwater fish and Daphnia , 2001, Environmental toxicology and chemistry.

[6]  J. Meador.  THE INTERACTION OF PH, DISSOLVED ORGANIC CARBON, AND TOTAL COPPER IN THE DETERMINATION OF IONIC COPPER AND TOXICITY , 1991 .

[7]  R. W. Winner.  Bioaccumulation and toxicity of copper as affected by interactions between humic acid and water hardness , 1985 .

[8]  E. Tipping.  WHAM—a chemical equilibrium model and computer code for waters, sediments, and soils incorporating a discrete site/electrostatic model of ion-binding by humic substances , 1994 .

[9]  A. Bianchini,et al.  Sodium turnover rate determines sensitivity to acute copper and silver exposure in freshwater animals. , 2002, Comparative biochemistry and physiology. Toxicology & pharmacology : CBP.

[10]  D. Rorabacher,et al.  Noncomplexing Tertiary Amines as "Better" Buffers Covering the Range of pH 3-11. Temperature Dependence of Their Acid Dissociation Constants. , 1999, Analytical chemistry.

[11]  C. Wood.  Flux measurements as indices of H+ and metal effects on freshwater fish , 1992 .

[12]  L. Sigg,et al.  Binding of Cu(II) to algae in a metal buffer , 1990 .

[13]  Colin R. Janssen,et al.  Predicting acute zinc toxicity for Daphnia magna as a function of key water chemistry characteristics: Development and validation of a biotic ligand model , 2002, Environmental toxicology and chemistry.

[14]  Colin R. Janssen,et al.  Development and field validation of a predictive copper toxicity model for the green alga Pseudokirchneriella subcapitata , 2003, Environmental toxicology and chemistry.

[15]  E. Tipping.  Modelling ion binding by humic acids , 1993 .

[16]  D. Dixon,et al.  Copper accumulation on gills of fathead minnows: Influence of water hardness, complexation and pH of the gill micro‐environment , 1992 .

[17]  C. Wood,et al.  Physiological effects of chronic copper exposure to rainbow trout (Oncorhynchus mykiss) in hard and soft water: Evaluation of chronic indicators , 2000 .

[18]  E. Tipping,et al.  Testing a humic speciation model by titration of copper-amended natural waters , 1998 .

[19]  F. Morel,et al.  Characterization of Organic Copper-Complexing Agents Released by Daphnia magna , 1983 .

[20]  S. Luoma.  Reassessment of metals criteria for aquatic life protection , 1997 .

[21]  Colin R. Janssen,et al.  Effects of dissolved organic carbon concentration and source, pH, and water hardness on chronic toxicity of copper to Daphnia magna , 2004, Environmental toxicology and chemistry.

[22]  Colin R. Janssen,et al.  Biotic ligand model development predicting Zn toxicity to the alga Pseudokirchneriella subcapitata: possibilities and limitations. , 2002, Comparative biochemistry and physiology. Toxicology & pharmacology : CBP.

[23]  Colin R. Janssen,et al.  A biotic ligand model predicting acute copper toxicity for Daphnia magna: the effects of calcium, magnesium, sodium, potassium, and pH. , 2002, Environmental science & technology.

[24]  S. Cabaniss,et al.  Copper binding by dissolved organic matter: II. Variation in type and source of organic matter , 1988 .

[25]  P. Paquin,et al.  Biotic ligand model of the acute toxicity of metals. 1. Technical Basis , 2001, Environmental toxicology and chemistry.

[26]  Colin R. Janssen,et al.  Refinement and field validation of a biotic ligand model predicting acute copper toxicity to Daphnia magna. , 2002, Comparative biochemistry and physiology. Toxicology & pharmacology : CBP.

[27]  E. Tipping,et al.  Comparison of measured and modelled copper binding by natural organic matter in freshwaters. , 2002, Comparative biochemistry and physiology. Toxicology & pharmacology : CBP.

[28]  W. Sunda,et al.  Effect of complexation by natural organic ligands on the toxicity of copper to a unicellular alga, Monochrysis lutheri1 , 1978 .

[29]  G. K. Pagenkopf.  Gill surface interaction model for trace-metal toxicity to fishes: role of complexation, pH, and water hardness , 1983 .

[30]  Colin R. Janssen,et al.  Uncertainties in the Environmental Risk Assessment of Metals , 2000 .

[31]  Duane A. Benoit,et al.  The effects of water chemistry on the toxicity of copper to fathead minnows , 1996 .