EXECUTIVE SUMMARY
As part of the Aquatic Effects Technology Evaluation (AETE) Program, a field survey was conducted of the Lupin Mine in the Northwest Territories. This site has been suggested as a candidate for detailed testing of monitoring tools in 1997 studies sponsored by the AETE Program. The purpose of this survey was to provide information on whether or not to include this site in 1997 and, if so, for what particular hypotheses.
As part of this field survey, available historical information was reviewed. Transitory changes in water quality (copper, zinc, arsenic concentrations) have occurred related to effluent discharges. Historic data provided evidence for metals accumulation in sediments but no clear relationship between contamination and biological effects. Metallothionein measurements have not been made. Lake trout have elevated arsenic concentrations in their livers apparently related to the effluent discharge, but again there is no evidence of adverse effects related to this contamination.
Effluent discharge only occurs over a two week period in the summer; because the field survey was conducted in September soon after the work was contracted, neither effluent quality nor water quality during discharge could be assessed. However, data from the mine indicate the effluent is not acutely toxic nor are Permit limits exceeded.
Field studies were conducted at an exposure area (Sun Bay) and a reference area (South Bay), both in Contwoyto Lake. Significant elevations in some parameters occurred at the reference area compared to the exposure area. Some parameters exceeded Canadian freshwater guidelines for the protection of aquatic life at both exposure and reference areas. However, no conclusions are possible relative to conditions during effluent discharge, since the mine was not discharging.
Sediments showed significant elevations in some metals at the exposure area compared to the reference area. Arsenic was identified as a contaminant of concern in both areas relative to Canadian interim sediment quality criteria; nickel was identified as such only in the exposure area. However, arsenic (and most other metals) concentrations in the reference area are comparable to pre-discharge concentrations.
There was no significant difference between reference and exposure areas for total abundance or species richness of the benthos. However, some species were specific to one area and not the other, and habitat differences between the two areas may have confounded the comparison.
Three fish species (lake trout, round whitefish, lake cisco) were collected in sufficient numbers to be considered potential sentinel species; an additional species, burbot, was collected in low numbers but in both areas. Overall, catches were not abundant, and neither tissue nor metallothionein analyses were conducted due to the relative paucity of the catches. Additional information regarding this site is provided in Table ES-1.
Overall, the exposure and reference areas were judged acceptable for 1997 studies by the AETE Program. Fish can be collected with reasonable effort; burbot is the preferred sentinel species (if adequate numbers can be collected using angling or trap nets). Sediments and historic water quality data show differences between reference (lower) and exposure areas (higher) for some parameters. Sediment quality triad-type studies can be conducted.
