Fish from Peace, Athabasca and Slave rivers and their tributaries are exposed to a variety of pulp mill, municipal and industrial effluents (EnviResource 1995; Brown and Vandenbyllaardt, 1996). Assessments of effects of contaminants have focussed on chlorinated organic compounds, such as dioxins and furans (Pastershank and Muir, 1995), and on alterations of parameters affecting reproduction physiology in individual fish (Brown et al., 1993; Brown et al., 1996; Lockhart et al., 1996). These studies have demonstrated that there is exposure to organic contaminants because mixed function oxidase activities are elevated (Lockhart, et al., 1996; Lockhart and Metner, 1996); and that fish collected downstream from the pulp mills may be stressed, because they exhibit a high percentage of sexually immature individuals, and they have depressed circulating concentrations of gonadal steroid hormones (Brown et al., 1993; Brown et al., 1996).
The purpose of the research described in this report was to initiate studies to see if metals may be contibuting to these stresses. The objective was to evaluate whether the metal-binding protein, metallothionein, was elevated in organs of burbot, longnose sucker, northern pike or flathead chub collected downstream from pulp mills and other effluent discharge points, and whether there was evidence of cumulative impacts with progression downstream in these rivers. An increase in MT concentrations in fish represents a molecular response that generally indicates exposure and development of resistance to toxicity to metals, especially Cd, Cu, Hg and Zn (Klaverkamp et al. 1991; Roesijadi, 1992). The study was designed by the Northern River Basins Study Science Directors and the Contaminants Component Leader, and was based on selecting fish collection sites on their proximity to discharges from pulp mills. Additional information on fish collection sites and on general biological parameters of fish collected in 1994 is presented in other reports (EnviResource
1995; Brown et al. 1996).
Two observations were made, both in burbot, which may indicate exposure to elevated metal concentrations and the presence of cumulative impacts. First, the greatest difference in MT concentrations between collection sites was observed in kidney of burbot collected in the Slave River Delta (SRD) of Great Slave lake. MT concentrations in kidneys from these fish ranged from approximately 7-times to 26-times higher than those concentrations found in kidneys of burbot from other collection sites. MT concentrations in gill of burbot from SRD were also the highest observed. The SRD burbot may be exposed to metals due to natural conditions of high mineralization in the Great Slave Lake Delta or other parts of the lake; or these fish may be exposed to metals discharged by mining operations, such as the decommissioned lead-zinc mine at Pine Point. The counterclockwise current in this portion of the lake could transport metals from a western source, such as Pine Point, to the Slave Delta (English, 1984). Second, a progressive increase in MT concentration in proceeding from upstream fish collection sites to downstream sites was observed in concentrations of MT in burbot liver. In the Peace River and associated tributaries (Little Smoky, Smoky, and Wapiti), there is a progressive increase of up to 3.34-fold in burbot liver [MT] moving from upstream to downstream collection sites. In the upper Athabasca River system, there is a progressive increase of up to 2.33-fold in burbot liver [MT] moving from upstream to downstream collection sites.