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Prediction of mono‐, bi‐, and trivalent metal cation relative toxicity to the seaweed Gracilaria domingensis (Gracilariales, Rhodophyta) in synthetic seawater
Author(s) -
Mendes Luiz Fernando,
ZambottiVillela Leonardo,
Yokoya Nair Sumie,
Bastos Erick Leite,
Stevani Cassius Vinicius,
Colepicolo Pio
Publication year - 2013
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.2340
Subject(s) - metal , chemistry , artificial seawater , metal ions in aqueous solution , seawater , aqueous solution , electronegativity , ionic radius , ionic bonding , ion , biology , organic chemistry , ecology
The present study reports a 48‐h aquatic metal‐toxicity assay based on daily growth rates of the red seaweed Gracilaria domingensis (Gracilariales, Rhodophyta) in synthetic seawater. The median inhibitory concentration (IC50) for each metal cation was experimentally determined, and the ratios of free ions (aqueous complex) were calculated by software minimization of the total equilibrium activity (MINTEQA2) to determine the free median inhibitory concentration (IC50F). A model for predicting the toxicity of 14 metal cations was developed using the generic function approximation algorithm (GFA) with log IC50F values as the dependent variables and the following properties as independent variables: ionic radius ( r ), atomic number ( AN ), electronegativity ( X m ), covalent index ( X m 2 r ), first hydrolysis constant (|log K OH |), softness index (σ p ), ion charge ( Z ), ionization potential (Δ IP) , electrochemical potential (Δ E o ), atomic number divided by ionization potential ( AN/ Δ IP ), and the cation polarizing power for Z 2 /r and Z/AR . The 3‐term independent variables were predicted as the best‐fit model (log IC50F: –23.64 + 5.59 Z/AR + 0.99 | log K OH | + 37.05 σ p ; adjusted r 2 : 0.88; predicted r 2 : 0.68; Friedman lack‐of‐fit score: 1.6). This mathematical expression can be used to predict metal–biomolecule interactions, as well as the toxicity of mono‐, bi‐, and trivalent metal cations, which have not been experimentally tested in seaweed to date. Quantitative ion–character relationships allowed the authors to infer that the mechanism of toxicity might involve an interaction between metals and functional groups of biological species containing sulfur or oxygen. Environ Toxicol Chem 2013;32:2571–2575. © 2013 SETAC