Effects of natural organic matter source on reducing metal toxicity to rainbow trout (Oncorhynchus mykiss) and on metal binding to their gills

Abstract

Juvenile rainbow trout (Oncorhynchus mykiss, 3 g) were exposed for 74 h in ion-poor (soft) water to a mixed-metal solution in the presence of 4, 6, and 10 mg C/L natural organic matter (NOM). The metals were 0.2 microM Pb, 0.1 microM Hg, 0.1 microM Cd, 1.3 microM Cu, 0.05 microM Ag, and 3.5 microM Co, and the natural organic matter was isolated by reverse osmosis from three sources in southern Ontario, Canada. The six-metal solution alone was extremely toxic to the fish. Increasing concentrations of each NOM increased trout survival, but the NOM having the most allochthonous properties (from Luther Marsh) increased fish survival most, while the NOM having the most autochthonous properties (from Sanctuary Pond, Point Pelee) increased fish survival least. This pattern was reflected in the degree of reduction of Pb and Cu accumulation by the gills. Relatively simple chemical characterization of NOM, such as protein-to-carbohydrate ratios, or optical characterization, such as absorbance-to-fluorescence ratios (e.g., representing aromaticity), may adequately reflect these biologically relevant differences in organic matter quality.

Evaluating the ameliorative effect of natural dissolved organic matter (DOM) quality on copper toxicity to Daphnia magna: improving the BLM

“…elevation appears to have been negligible. Given the observed similarity in water chemistry of the exposure water in all other treatments, variability in Cu LC 50 to D. magna supports the source-dependent phenomenon reported earlier by Richards et al (2001), Ryan et al (2004), Schwartz et al (2004) andDe Schamphelaere et al (2004). In the following sections, the absorbance and fluorescence indices as quality predictors of DOMs are explored and discussed for their influence on the protective effect of DOMs against Cu toxicity (Cu LC 50 ) to D. magna.…”

“…For multiple regression models, data for AHA were excluded from the analysis based on statistical criteria as outliers, especially for SAC 340 data, and the fact that AHA as a humic substance is not a real aquatic DOM (Malcolm and MacCarthy 1986). Since SAC 340 is supported by previous research for its strong influence on Cu toxicity (De Schamphelaere et al 2004;Richards et al 2001;Ryan et al 2004;Schwartz et al 2004), the method for placing SAC 340 in models was the forced entry, while backward stepwise entry was used for the other variables, according to the guidance of Field (2005). Although octanol solubility showed no correlation with LC 50 in the presence of 3 mg C l -1 , this quality parameter was also added to the aforementioned predictors based on its significant relationship with LC 50 at 6 mg C l -1 .…”

“…The former tends to be optically darker, composed of larger molecules with a higher aromatic content, while the latter is optically lighter, and composed of smaller molecules with lower aromatic content (Richards et al 2001;Ryan et al 2004;De Schamphelaere et al 2004;Schwartz et al 2004). In addition, characterization and toxicological data recently compiled by Al-Reasi et al (2011) revealed that fluorophore concentrations obtained by PARAFAC, as another potential DOM quality parameter, explain considerable variability in the protective effects against Cu toxicity.…”

“…Recent studies have indicated that protection may also be source-dependent (e.g. Richards et al 2001;Ryan et al 2004;Schwartz et al 2004), highlighting the possible influences of chemical structure and composition of DOM source on its protective ability.…”

Watershed land use as a determinant of metal concentrations in freshwater systems

“…In fish, the embryonic and larval stages are usually the most sensitive to metals. The metal-gill interactions model takes into account metal speciation in water and the interactions between cations, anions, and organic ligands which can compete in solution for metals and decrease binding to the gill ligands (McGeer et al 2000;Richards et al 2001).…”