Research Priorities > Impacts Domain
 

Detection of Metal-Induced Effects in Indigenous Fauna and Flora
  Research Team
P.G.C. Campbell, (Université du Québec, INRS-Eau) - PI; L. Chan, (McGill University); G. Dixon, (University of Waterloo); A. Hontela (Université du Québec à Montréal); J. Rasmussen, (McGill University); U. Borgmann (NWRI); T. Scheuhammer (CWS)

 
  Summary
Attempts to define the impacts of metals on aquatic ecosystems have traditionally involved laboratory experiments under defined conditions (toxicity tests) and, to a lesser extent, field observations on impacted indigenous populations (abundance; condition; growth; reproduction) [1]. To link these two approaches, one needs a common measure of metal exposure in laboratory and field settings. The determination of metal concentrations or burdens in tissues (or whole organisms) has been suggested as a means of achieving this linkage. In the present project we propose to explore this approach with aquatic biota, and to expand the concept of metal Abody burden@ to take into account the speciation of the metal within the organism, i.e. the organism=s ability to detoxify the metal. The aquatic biota to be considered include benthic invertebrates, indigenous fish and waterfowl.

 
  Scientific Background

Aquatic organisms can take up metals, both essential and non-essential, from water and/or food. For both modes of uptake, the total metal concentration [M]T (i.e., in the water column or in the diet) is an unreliable indicator of how much metal will be taken up by the organism. To predict metal bioaccumulation one must consider the speciation of the metal, some metal forms being more "bioavailable" than others [2].

The concept of metal speciation and its relevance to metal bioavailability do not stop at the biological surface, however. Once within the organism the metal can be directed to different tissues, to different compartments (vacuoles, granules, concretions, cytosol, ...), within each of these compartments the metal will tend to partition among different ligands [3]. Intuitively one would expect the intracellular bioavailability of a metal, i.e. its effects (deleterious or otherwise) on the host organism after absorption, to vary as a function of its tissue distribution and its intracellular partitioning within a given tissue. The corollary is that relations between metal body burdens in aquatic organisms and metal-induced effects at the organism, population and community levels are likely to be improved if the metal body burdens are expressed not as total metal ... but rather in terms of the metal=s partitioning within particular target tissues.

The long-term objectives of the project are thus (i) to demonstrate a mechanistic link between the intracellular speciation of metals and the manifestation of deleterious effects at the organism and population levels, and (ii) to provide rationale/validated measurement endpoints for the ecological risk assessment of metals.

 
  Practical Background
Over the time frame 1998-2004 we propose to test relations between metal body burdens in aquatic organisms and metal-induced effects at the organism, population and community levels at three levels: with aquatic invertebrates (Dixon and Borgmann), with indigenous fish (Campbell, Hontela, Rasmussen) and with waterfowl (Chan and Scheuhammer). Various funding options are being explored for the period 1999-2004 (e.g., applications to NSERC for University-Industry funding in the <Research Network> or <Cooperative Research and Development> areas). However, since we could not realistically expect to receive levered funding until 1999 at the earliest (i.e., well after the 1998-99 field season), we designed the 1998-99 research program on the basis of a budget of $75,000.

 
  Overall Goals
An overriding goal for the current funding exercise was to maintain and foster interactions among those MITE researchers who are involved in research on the impacts of metals in the environment. The 1998-99 time-frame was thus seen as a transition year, during which these contacts were maintained even while we worked on obtaining complementary funding from NSERC and other sources. Each sub-project was designed to test certain key hypotheses and to yield short-term results that will help us to refine the experimental approached for the subsequent field work.

 
  References

[1] Munkittrick, K.R. and D.G. Dixon. 1989. Use of white sucker (Catostomus commersoni) populations to assess the health of aquatic ecosystems exposed to low-level contaminant stress. Can. J. Fish. Aquat. Sci. 46:1455-1462.

[2] Campbell, P.G.C. 1995. Interactions between trace metals and organisms: critique of the free-ion activity model. In Tessier, A. & Turner, D. [Eds.], Metal Speciation and Bioavailability in Aquatic Systems. J. Wiley & Sons, Chichester, UK, pp.102.

[3] Roesijadi, G. and W.E. Robinson. 1994. Metal regulation in aquatic animals: mechanisms of uptake, accumulation, and release. In: Aquatic toxicology. Molecular, biochemical, and cellular perspectives. D.C. Malins and G.K. Ostrander, editors. Lewis, Boca Raton, pp. 387-420.