EXECUTIVE SUMMARY
The Aquatic Effects Technology Evaluation (AETE) Program was established to conduct field and laboratory evaluation and comparison of selected environmental effects monitoring technologies for assessing impacts of mine effluents on the aquatic environment. Field evaluations were conducted at seven mine sites in 1996 to determine which sites were suitable for further evaluation in 1997. This final field survey report provides detailed information on work conducted at the Gaspé Mine site in Murdochville, Quebec.
The 1996 field survey at Gaspé Mine involved the following study/field components:
- historical data review;
- sublethal toxicity testing;
- habitat characterization and classification;
- water chemistry sampling;
- benthic invertebrate sampling;
- fish population sampling; and
- fish tissue collection.
A summary of the results of the 1996 survey at the Gaspé Mine are presented in the executive summary table. The 1996 field survey results indicated that the Gaspé Mine site meets some of the suitability criteria for hypothesis testing in 1997. The evaluation of the suitability of this site is presented in the report.
An extensive historical database exists for the site with respect to effluent and water chemistry data, benthic invertebrate community data and fisheries population data. This data was valuable for selection of sampling stations and comparison of results with those from the 1996 study. The Gaspé Mine site was easily accessible and multiple reference and exposure areas were available of uniform habitat type and substrate composition. The municipal sewage treatment plant discharges into the reclaim basin upstream of the exposure area. However this discharge is not considered to be a major confounding factor relative to the discharge of the mine effluent and water chemistry analyses in the exposure area and of the effluent did not illustrate a nutrient enrichment effect. Effluent is discharged continuously at the site. Sublethal toxicity testing was conducted on the effluent but testing did not clearly illustrate toxicity except to Ceriodaphnia dubia reproduction and Lemna minor growth. However, sublethal toxicity testing of the effluent in future studies should not be ruled out based upon the results of the 1996 survey due to several confounding factors including toxicity of the Miller River receiving water and invalid test results. It is recommended for future studies involving sublethal toxicity testing, that receiving (dilution) water be collected in the North Branch of the York River, all sublethal tests be performed on effluent collected on the same day, and sublethal tests be conducted on more than one occasion to obtain as estimate of testing variability.
Suitable, representative depositional areas did not exist for sediment sampling. As a result, the water column represents the main source of exposure of aquatic biota to metals discharged from the mine site. A significant difference in general water chemistry and total and dissolved metals existed between the reference and exposure areas.
Results from the benthic invertebrate sampling program showed significant differences in total species richness and richness of sensitive species between areas. Total species abundance did not differ between areas.
Juvenile Atlantic salmon and brook trout were the dominant species in both areas and were abundant. Future population studies should focus on juvenile Atlantic salmon as this species was more abundant and has been sampled historically. Differences in CPU, growth and condition of sentinel species could be evaluated at the Gaspé Mine site based upon the results of the 1996 field surveys. However, comparative studies of growth of juvenile salmon populations would be restricted by the limited age classes present at the site. Metallothionein (MT) was a good indicator of exposure at the Gaspé Mine site with concentrations in whole fish from the exposure area being significantly higher than those sampled from the reference area. Metal concentrations (Zn+Cu+Cd) were related to the MT results. Future studies on fish tissue are possible at this site with two restrictions. Firstly, a barrier does not exist at the site to eliminate the possibility of fish migration between the reference and exposure areas. Thus, caged fish would be a suitable alternative for evaluating effluent exposure at this site. Secondly, as only small fish are available in the North and South Branches of the York River, comparisons of different tissue burdens could not be evaluated as the fish are too small for dissection.
