Development and field validation of a predictive copper toxicity model for the green alga Pseudokirchneriella subcapitata

Abstract

In this study, the combined effects of pH, water hardness, and dissolved organic carbon (DOC) concentration and type on the chronic (72-h) effect of copper on growth inhibition of the green alga Pseudokirchneriella subcapitata were investigated. Natural dissolved organic matter (DOM) was collected at three sites in Belgium and The Netherlands using reverse osmosis. A full central composite test design was used for one DOM and a subset of the full design for the two other DOMs. For a total number of 35 toxicity tests performed, 72-h effect concentration resulting in 10% growth inhibition (EbC10s) ranged from 14.2 to 175.9 micrograms Cu/L (factor 12) and 72-h EbC50s from 26.9 to 506.8 micrograms Cu/L (factor 20). Statistical analysis demonstrated that DOC concentration, DOM type, and pH had a significant effect on copper toxicity; hardness did not affect toxicity at the levels tested. In general, an increase in pH resulted in increased toxicity, whereas an increase of the DOC concentration resulted in decreased copper toxicity. When expressed as dissolved copper, significant differences of toxicity reduction capacity were noted across the three DOM types tested (up to factor 2.5). When expressed as Cu2+ activity, effect levels were only significantly affected by pH; linear relationships were observed between pH and the logarithm of the effect concentrations expressed as free copper ion activity, that is, log(EbC50Cu2+) and log(EbC10Cu2+): (1) log(EbC50Cu2+)= - 1.431 pH + 2.050 (r2 = 0.95), and (2) log(EbC10cu2+) = -1.140 pH -0.812 (r2 = 0.91). A copper toxicity model was developed by linking these equations to the WHAM V geochemical speciation model. This model predicted 97% of the EbC50dissolved and EbC10dissolved values within a factor of two of the observed values. Further validation using toxicity test results that were obtained previously with copper-spiked European surface waters demonstrated that for 81% of tested waters, effect concentrations were predicted within a factor of two of the observed. The developed model is considered to be an important step forward in accounting for copper bioavailability in natural systems.

Evaluating the effects of pH, hardness, and dissolved organic carbon on the toxicity of aluminum to freshwater aquatic organisms under circumneutral conditions

“…The DOC effects evaluated in the present study were based on laboratory exposures to Suwannee River NOM, which is a commonly used natural form of DOC for metal toxicity studies. Although it is recognized that natural forms of DOC can vary in composition and, hence, their metal binding properties [35], the effects of DOC complexation even in the face of this variability is well characterized using bioavailability-based models [15,16]. Although water quality effects on algal toxicity were broadly similar, hardness relationships differed markedly with pH.…”

Humic Ion-Binding Model VII: a revised parameterisation of cation-binding by humic substances

“…Examples include 71 the acidification of soils [7][8][9][10][11][12][13][14] and surface waters [15] , trace metal behaviour in soils [16][17][18][19][20][21][22] , surface 72 waters [23][24][25][26][27][28][29][30][31] and groundwaters [32] , lake sediment diagenesis [33,34] , rare earth geochemistry [35-73 37] , iron and manganese geochemistry [38][39][40][41] , radionclide geochemistry [42][43][44][45] , organic matter 74 solubility in soils [46,47] , catchment modelling [48,49] , interactions of metals with biota [50,51] , 75 ecotoxicology [52][53][54][55][56][57][58][59] and Critical Loads …”

Estudo dos mecanismos de detoxificação e tolerância aos metais cromo e cobre em Pseudokirchneriella subcapitata e Pistia stratiotes e o uso das macrófitas Typha sp e Phragmites sp na remoção de nutrientes em wetlands construídos

“…Similar results were observed for us in leaves of P. stratiotes to both enzymes. Srivastava et al (2006) suggested that, high increase in activities of these enzymes could mean a breakdown of SCHAMPHELAERE et al 2003). Statistical advancement in ecotoxicology is necessary to improve the guidelines in this area.…”

“…The disadvantage of this type of design is twofold: the effect of only one parameter is studied, and possible interactions of different parameters cannot be assessed . In contrast, the advantage of the Central Composite Design (CCD) is that it can generate a maximum amount of information on the direct effect of test variables and their interactions while testing a minimum number of combinations (DE SCHAMPHELAERE et al, 2003).Thus, a way to develop, improve and optimize processes consists of applying the CCD and the Response Surface Methodology (RSM), which can be very useful and advantageous for both the evaluation and optimization of some capacidade parameters. More specifically, the experimental design helps the researcher to verify if changes in the independent variables produce a statistically significant variation of the observed response, and this approach can be used each time this type of information is required (FURLANETTO et al, 2003).…”

“…Similarly to the use of multivariate methods which have proven to be efficient for analyzing datasets with complex inter-relationships among the variables (SINHA et al, 2009) the use of the Central Composite Design (CCD) is advantageous; it can generate a maximum amount of information on the direct effect of test variables and their interactions while testing a minimum number of combinations (DE SCHAMPHELAERE et al 2003). Statistical advice in current ecotoxicity test guidelines is in need of improvement, and the recent use of the factorial design in this area has presented promising results, which generate predictive models of toxicity to aquatic organisms.…”