Assessing effects of dissolved organic carbon and water hardness on metal toxicity to Ceriodaphnia dubia using diffusive gradients in thin films (DGT)

Environmental context Interaction of metals with dissolved organic matter is one of the key processes defining metal bioavailability in water. The technique of diffusive gradients in thin films was used to investigate the kinetics of the interaction between metals and dissolved organic matter released by algae. For most metals the rate at which they were released from the organic matter was fast, but release of iron was kinetically limited. AbstractThe interaction of metals with organic matter is one of the key processes determining metal speciation and bioavailability in water. Fulvic acid tends to dominate dissolved organic carbon (DOC) in freshwaters, but organic carbon produced in situ, e.g. exudates released by algae and bacteria, is also significant. The technique of diffusive gradients in thin films (DGT) was used to investigate the lability of metal–exudate complexes using a kinetic signature approach. Exudates were harvested from three cultured freshwater alga (Chlorella vulgaris, Cryptomonas pyrenoidifera, Anabaena flos-aquae) and the filtered media supplemented with trace metals. DGT-labile metal concentrations and kinetic signatures were determined (24-h deployment). The relationship between Fe and DOC was a defining feature of the kinetic signatures. Iron was the most kinetically limited metal followed by Al and Cu, whereas Co, Ni and Pb were effectively completely labile. Exudates from Chlorella vulgaris produced the most DOC and the most marked kinetic limitation.

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Relationship of Mercury Concentrations in Lake Trout (Salvelinus namaycush) and Smallmouth Bass (Micropterus dolomieui) to the Physical and Chemical Characteristics of Ontario Lakes

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f89-057 ◽

1989 ◽

Vol 46 (3) ◽

pp. 426-434 ◽

Cited By ~ 92

Author(s):

Michael J. McMurtry ◽

Donna L. Wales ◽

Wolfgang A. Scheider ◽

Gail L. Beggs ◽

Patricia E. Dimond

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Lake Trout ◽

Water Hardness ◽

Salvelinus Namaycush ◽

Smallmouth Bass ◽

Stepwise Multiple Regression ◽

Lake Area ◽

Micropterus Dolomieui ◽

The Relationship

Concentrations of mercury in dorsal muscle tissue of lake trout (Salvelinus namaycush) from Ontario lakes were positively correlated with variables indicating lake dystrophy (dissolved organic carbon, colour, iron, transparency) and were also correlated with watershed area and lake area. Stepwise multiple regression selected dissolved organic carbon as the only variable which explained a significant amount of variation (37%) in mercury concentrations in lake trout. The relationship between dissolved organic carbon and mercury appeared to be strongest in the group of lakes with values of dissolved organic carbon less than 4.0 mg∙L−1. In contrast, mercury concentrations in smallmouth bass (Micropterus dolomieui) were correlated with variables reflecting both water hardness (magnesium, calcium, conductivity) and acidity (pH, alkalinity). The relationship was inverse for the water hardness variables and positive for acidity. Stepwise regression identified three variables significant in explaining variation in mercury in smallmouth bass: calcium, dissolved organic carbon, and latitude. Mechanisms that may explain the effects of organic matter, water hardness, and acidity on mercury accumulation by fish are discussed.

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