Cadmium Ecophysiology in Seven Stonefly (Plecoptera) Species:  Delineating Sources and Estimating Susceptibility

Abstract

A major challenge in ecotoxicology lies in generating data under experimental conditions that are relevant to understanding contaminant effects in nature. Biodynamic modeling combines species-specific physiological traits to make predictions of metal bioaccumulation that fare well when tested in the field. We generated biodynamic models for seven predatory stonefly (Plecoptera) species representing the families Perlidae (5) and Perlodidae (2). Each taxon was exposed to cadmium independently via diet and via solution. Species varied approximately 2.6 fold in predicted steady-state cadmium concentrations. Diet was the predominant source of accumulated cadmium in five of the seven species and averaged 53.2 +/- 9.6% and 90.2 +/- 3.7% of net Cd accumulation in perlids and perlodids, respectively. Differences in Cd bioaccumulation between the two families were largely driven by differences in dissolved accumulation rates, which were considerably slower in perlodidsthan in perlids. We further examined the subcellular compartmentalization of Cd accumulated from independent aqueous and dietary exposures. Predicted steady-state concentrations were modified to only consider Cd accumulated in metal-sensitive subcellular compartments. These values ranged 5.3 fold. We discuss this variability within a phylogenetic context and its implications for bioassessment.

Aquatic insect ecophysiological traits reveal phylogenetically based differences in dissolved cadmium susceptibility

“…We offer a few possible explanations for this. First, the efflux rate constant k e applies to both dissolved and dietary exposure routes (14) and is arguably the most important determinant of bioaccumulation (17). Second, we have already established that uptake rates of Cd and zinc (Zn) covary strongly among species (12), so our rate constants of Cd uptake are likely also reasonable approximations for Zn.…”

“…These fractions included cell debris, cellular organelles, microsomes, cytosolic proteins denatured by heat treatment (heat-denatured proteins, HDPs), and HSPs. In previous papers, we have referred to these cytosolic protein fractions as metallothionein-like proteins and nonmetallothionein-like proteins (13,14,21). Here, we have changed our nomenclature because our recent work has failed to demonstrate the presence of cysteine-rich, metallothionein-like proteins in the HSP fractions of various aquatic insects.…”

“…This variation in susceptibility has practical implications, because the ecological structure of aquatic insect communities is often used to indicate the ecological conditions in freshwater systems (7)(8)(9). Differences among species' responses to environmental stressors can be profound, but it is uncertain whether the cause is related to functional ecology [usually the assumption (10, 11)] or physiological traits (5,(12)(13)(14), which have received considerably less attention. To the degree that either is involved, their link to phylogeny and evolutionary history remains poorly understood.…”

“…18 and 20). We have used this integrated approach to reconcile apparent discrepancies between insect responses to trace metals in toxicity assays and in nature (13), to infer Cd sensitivity differences among predaceous stoneflies (14), and to understand the mechanisms underlying the metal tolerance of a caddis fly (21).…”

Bioaccumulation of Heavy Metals and Hydrocarbons in Hemichromis Fasciatus Exposed to Surface Water in Borrow Pits Located Within Onshore Oil Exploration and Production Area

“…Many laboratories bioaccumulation studies have been reported by researchers (Wang & Rainbow, 2006;Noegrohati, 2006;Martin et al, 2007;Kamunde, 2009). However, field bioaccumulative studies, gives a real situation approach, whereby aquatic organisms are exposed to retinue of inorganic and organic compounds that interplays within the natural environment.…”