Cadmium bioaccumulation assays. Their relationship to various ionic equilibriums in Lake Superior water

The alga Selenastrum capricornutum Printz is used to investigate the potential of natural lake water to reduce cadmium toxicity. The two lakes involved differ in trophic status and in concentration and composition of dissolved organic matter, one being a typical dystrophic bog lake, the other a less humus influenced, eutrophic lake. In the dystrophic lake, the toxic effect is determined mainly by the free cadmium activity. In the eutrophic, less humus influenced lake, however, the toxic effect shows considerable seasonal variations with a toxicity far exceeding what would be expected according to the estimated free ion activity during summer.It is hypothesized that qualitative changes in the composition of the dissolved organic matter during the production period are responsible for this effect.

Section: Discussionsupporting

confidence: 54%

Seasonal variation of cadmium toxicity toward the alga Selenastrum capricornutum Printz in two lakes with different humus content

Lægreid¹,

Alstad²,

Klaveness³

et al. 1983

“…The bioavailability of cadmium in the presence of DOM depends on the organism under investigation and the kind and concentration of DOM. For some species the bioaccumulation or toxicity of cadmium was found to be in accordance with the FIAM (14,(22)(23)(24)(25). On the other hand, in some studies concerning bivalve molluscs, the accumulation of cadmium increased in the presence of DOM (26)(27)(28).…”

Section: Introductionmentioning

confidence: 76%

Cadmium Bioavailability and Accumulation in the Presence of Humic Acid to the Zebra Mussel, Dreissena polymorpha

Voets

Bervoets

Blust

2004

Metal speciation in aquatic systems is mainly determined by the type and concentration of ligands present in solution. A very important group of complexing agents is dissolved organic matter (DOM), e.g., humic and fulvic acids. According to the free-ion activity model, only the free metal ion is available to biota. Nevertheless, DOM has been reported to decrease or increase metal uptake, leading to uncertainty concerning the bioavailability of metal-DOM complexes. In this work the effect of Aldrich humic acid on cadmium accumulation by the zebra mussel, Dreissena polymorpha, was studied under laboratory conditions. Mussels, collected in a drinking water reservoir, were exposed to varying environmentally relevant concentrations of cadmium in the presence and absence of humic acid. Cadmium concentrations in the mussel tissues were analyzed, and measurements with a cadmium-ion-selective electrode were made to determine the free cadmium ion activity in the exposure waters. The uptake of humic acid by the zebra mussels was measured by the decrease of the total organic carbon (TOC) concentration in the water over time. The free cadmium ion activity in the water decreased from 51.6% to 19.9% of the total cadmium concentration in the presence of humic acid. This decrease by a factor of 2.6 resulted in a decrease in the cadmium uptake rate in the soft tissue of zebra mussels from 12.9 to 7.9 nmol/g dry wt/day, which corresponds to a decrease by a factor of 1.6. This implies that cadmium uptake rates were higher than predicted by the free-ion activity model and indicates that cadmium-humic acid complexes are partly available to zebra mussels.

“…Either mechanism may account for the positive correlation between Cdz and Cda(}. While the binding of Cd to natural or synthetic organic compounds does not always depress Cd availability (31)(32)(33), the negative correlation of Cdz with DOC is presumably attributable to the formation of relatively unavailable organo-Cd complexes in the waters of dystrophic lakes. Negative correlations between DOC and biotic Cd concentrations have also been recorded for aquatic amphipods and molluscs in Canadian Shield lakes (12,34).…”

Section: Resultsmentioning

confidence: 99%

Cadmium concentrations of crustacean zooplankton of acidified and nonacidified Canadian Shield lakes

Yan¹,

Mackie²,

Dillon³

1990

The cadmium in Epilimnetic zooplankton (Cdz) collected from 33 nonacidified, south central Ontario lakes, most of which were remote from local point sources of Cd emissions, ranged in concentration from 0.16 to 29.8 Mg/g of dry weight. Levels were positively correlated with aqueous Cd concentrations and negatively correlated with lake water Ca, organic carbon, and total phosphorus concentrations. A stepwise regression model developed for these lakes overestimated Cd concentrations in zooplankton from acidic (pH <5), clear-water lakes, presumably because the acidity of these lakes depressed Cd uptake. Cdz levels varied by 5-fold over the ice-free season in Plastic Lake, an acidifying lake in south central Ontario.While Cdz levels were not correlated with zooplankton composition in the lake survey, temporal variations in Cdz levels in Plastic Lake were attributed, in part, to seasonal and annual changes in zooplankton community structure in the lake.