EXECUTIVE SUMMARY

The Heath Steele (New Brunswick) mine study is one of four field evaluations carried out in 1997 under the Aquatic Effects Technology Evaluation (AETE) Program, a joint government-industry program to evaluate the cost-effectiveness of technologies for the assessment of mining-related impacts in the aquatic environment. The other three mines studied were Dome (Ontario), Mattabi (Ontario) and Myra Falls (British Columbia). Results of all four studies are summarized and evaluated in a separate summary report.

Heath Steele Division, Noranda Inc., is a base metal mine located northwest of Miramichi, in the Tomogonops River headwaters, which flows into the Northwest Miramichi River. The mine produces zinc, lead, copper and silver concentrations. The mine was first developed in the mid-1950s and, although great strides have been made in cleanup of acid rock drainage (ARD) and metal leaching problems in recent years, the mine continues to release substantial loadings of metals to the Little South Branch Tomogonops River due to the effects of ARD. These loadings are being progressively reduced.

The 1997 field studies were carried out in the Little South Branch Tomogonops River and downstream in the main Tomogonops River, upstream of any effect of the treated effluent from the tailings pond. Sampling was carried out here rather than downstream of the effluent because this reach offered an opportunity for study in a stronger water quality gradient. Sampling was not extended downstream of the treated effluent because of the confounding effects of a greatly increased water hardness in the river produced by calcium added in the form of lime for effluent treatment. The entire section of river studied here consists of riffle/run habitat, with a rock-cobble substrate.

The objectives of the 1997 field program were to test 13 hypotheses formulated under four guiding questions:

1. are contaminants getting into the system (and to what degree and in which compartments)?
2. are contaminants bioavailable?
3. is there a measurable (biological) response? and
4. are contaminants causing the responses?

The hypotheses are more specific questions about the ability or relative ability of different monitoring tools to answer these four general questions about mine effect. The evaluation of tools included: sediment monitoring (sediment toxicity tests); fish monitoring (tissue metallothionein and metal analyses, and population/community indicators), and; integration of tools (relationships between exposure and biological responses and use of effluent sublethal toxicity).

Of the 13 hypotheses, 8 were tested at Heath Steele as outlined in Table 1.1. The hypotheses not tested at Heath Steele include tissue comparisons of metals and metallothionein contents (because resident fish are small and analyses were of whole gut rather than individual organs), and sediment-related hypotheses because no soft sediment occurs in the affected reach. One sediment-related hypothesis was tested at Heath Steele (linkage between benthos and sediment quality) using periphyton as a surrogate for sediment.

Study Design

The study design at Heath Steele was based on river sampling for fish and benthos using a gradient design, including five exposure reaches and three reference reaches, with each reach consisting of two stations. Each exposure reach along the gradient had a different concentration of metals, with the key metals being zinc, copper, cadmium and lead. Three reference reaches were established to span the range of river size represented across the exposure gradient.

Sampling Program

The field survey at Heath Steele was completed in August 1997, and included:

• water sampling at each of 16 stations (8 reaches) where fish and benthos were sampled;
• benthic sampling at each of 16 stations (2 samples at each) using a T-sampler;
• periphyton sampling at each of 16 stations (2 samples at each) carried out by scraping of rock substrate surfaces;
• fish population and community at each of 16 stations using a standard electrofishing effort;
• collection of up to 134 juvenile Atlantic salmon and 47 blacknose dace for measurement of length, weight and age (by length frequency analysis with confirmatory aging). Some stations produced no salmon or dace, due to apparent toxicity at the most exposed sites and in one instance due to habitat limitations (fish migration barriers);
• collection of four viscera samples (where possible) per station from wild juvenile salmon (one fish per sample), one to six composite blacknose dace per station and variable numbers of brook trout at each station. In addition, two samples of viscera were collected from each of two caged juvenile salmon from a nearby salmon rearing facility exposed at each station for nine days; and
• three “effluent” samples for chronic toxicity testing using the Ceriodaphnia dubia survival and reproduction test, the fathead minnow survival and growth test, the Selenastrum capricornutum growth test and the Lemna minor growth test. “Effluent” consisted of water collected from the Little South Branch Tomogonops River at the location most affected by the mine and routinely monitored by mine personnel.

Data Overview

Water Quality

Total and dissolved (0.45 µm-filtered) concentrations of Zn, Cd, Pb, Cu, Al and Fe all showed concentration gradients downstream of Heath Steele. All of these parameters except Al remained elevated relative to reference site concentrations at the downstream extent of the exposure gradient, and all occurred in excess of Canadian Water Quality Guidelines in some or all exposure reaches (depending on the metal). Dissolved and total metal concentrations were similar for Zn, Cu and Cd, while dissolved Al, Fe and Pb were substantially lower than their total concentrations.

Periphyton

Periphyton samples were rich in species and variable in biomass, and no trends were observed in response to the water quality gradient or between exposed and reference reaches. In terms of metal concentrations in periphyton, exposed periphyton contained greater levels of Cd, Cu, Zn and Pb, although only Pb in periphyton appeared to track the water quality gradient in the exposure reaches.

Benthic Macroinvertebrates

Benthic community structure responded to the water quality gradient, with exposed stations showing reduced total numbers of taxa and reduced numbers of Ephemeroptera, Plecoptera and Trichoptera (EPT) taxa. Trends were also observed in apparent indicator taxa such as Micropsectra which was sensitive to high degrees of exposure, and Rheocricotopus which was most abundant at higher degrees of exposure. Total benthic density, however, appeared unresponsive to metal exposure.

Fish

Fish community structure varied from reach to reach, with juvenile Atlantic salmon densities suppressed upstream of the most downstream exposure reach, apparently due to a partial migration barrier. Ten species were represented in the collections, with juvenile salmon, blacknose dace, lake chub and brook being the most common. No fish were found at the most exposed station, apparently due to toxicity.

Catch-per-unit-effort (numbers) and biomass-per-unit-effort (all species) clearly responded to the exposure gradient, and gradually increased from upstream to downstream.

Fish size at age appeared unresponsive to exposure, although Atlantic salmon fry were larger in the exposure area than in the reference area. This effect is probably attributed to higher fry densities and greater competition in the reference area.

Metallothionein (MT) levels in fish viscera were greater in exposed salmon and dace than in reference fish. MT concentrations in caged juvenile salmon viscera and gill closely tracked metal concentrations in water after the exposure period.

Visceral metal levels appeared elevated in exposed wild fish for some metals, although this response was less evident in caged fish.

Effluent Toxicity

All effluent samples tested were chronically toxic to Ceriodaphnia, Selenastrum and Lemna, while sublethal and lethal toxicity occurred in two of the three tests in fathead minnow. The degree of toxicity corresponded with metal concentration in Ceriodaphnia and Selenastrum, while Lemna and fathead minnow responses did not appear to track metal concentrations in the samples.

Hypothesis Testing

Hypothesis testing results are summarized in Table 5.2. Results of testing indicate that some of the metals are bioavailable, that biological responses occur in both benthos and fish, and that metals appear to cause some of these responses.

Technology Evaluation

Many of the monitoring tools evaluated at Heath Steele demonstrated a mine effect. Periphyton community structure, fish growth and benthic community density were ineffective. Those tools that demonstrated mine effects or partially demonstrating mine effects included water quality, periphyton metals, fish viscera and gill metals and MT, fish population/community indicators, effluent chronic toxicity and benthic community indicators. Table 6.2 summarizes the effectiveness of the various tools tested at Heath Steele.

Among those tools compared in hypothesis testing, some appeared more effective than others. Table 6.3 provides a summary of tool comparisons.

Conclusions on the cost-effectiveness of the tools based on results from all four mine sites studied in 1997 are found in a separate document “Summary and Cost-Effectiveness Evaluation of Aquatic Effects Monitoring Technologies Applied in the 1997 AETE Field Evaluation Program”.