Third national assessment
- Executive Summary
- 1.0 Introduction
- 2.0 Methods
- 3.0 Presence or Absence of Effects
- 4.0 Effluent Quality
- 5.0 Biological Monitoring Studies Investigating Observed Effects
- 6.0 Key Findings
- 7.0 Glossary
- 8.0 References
- Appendix A: Metal Mines Subject to the Metal Mining Effluent Regulations in 2013
- Appendix B: Effect Indicators, Critical Effects Sizes and Studies Conducted
- Appendix C: Mine-by-Mine Results of Studies Assessing Potential Effects
- Appendix D: Fish Tissue Mean Total Mercury Concentrations per Mine
- Appendix E: Trends in Sublethal Toxicity
- Appendix F: Trends in Sublethal Toxicity for Ore Types
- Appendix G: Annual Mean Concentrations of Effluent Characterization Data
- Appendix H: Mine-by-Mine Summary of Investigation Studies
3.0 Presence or Absence of Effects
3.1 Overall Effects
Of the 82 mines that had completed two or more biological monitoring studies to assess effects on fish and/or fish habitat, 76% (62/82) confirmed the presence of at least one effect (Figure 1) and approximately half (32/62 or 52%) of these mines confirmed effects on both fish and fish habitat indicators. Ninety-two percent (57/62) of mines with confirmed effects observed at least one effect equal to or greater than the critical effect size (CES). This included 45 mines where the effect was equal to or greater than the CES in both consecutive studies used to confirm effects and 12 mines where the effect was equal to or greater than the CES in one study and less than the CES in the other study used to confirm effects. Variable results between consecutive studies were observed by 23% (19/82) of mines, resulting in unconfirmed effects. One mine confirmed the absence of effects on fish, fish habitat and the use of fisheries resources.
Figure 1. Effect categories for mines completing two or more studies to assess effects on fish and/or fish habitat
Description
Figure 1 is a pie chart illustrating effect categories for 82 mines completing two or more biological monitoring studies. The effect categories are shown in number of mines. The four types of effect categories identified in the graph are confirmed effects equal to or greater than CES (57), confirmed effects less than CES (5), unconfirmed effects (19) and confirmed absence of effects (1).
Of the 33 mines with a single completed biological monitoring study for both the fish and fish habitat components, 31 mines observed effects and 25 observed at least one effect equal to or greater than the CES. Two mines observed an absence of effects on all fish and fish habitat (benthic invertebrate community) indicators that were successfully assessed (Figure 2).
Figure 2. Effect categories for mines completing a single study to assess effects on fish and fish habitat
Description
Figure 2 is a pie chart illustrating effect categories for 33 mines completing one biological monitoring study. The effect categories are shown in number of mines. The three types of effect categories identified in the graph are effects equal to or greater than CES (25), effects less than CES (6) and absence of effects (2).
3.2 Effects on Fish
The indicators used to assess effects on fish include growth, reproduction, body and liver condition, and survival. Sixty-six mines completed at least two studies to assess effects on the fish population and 66% (44/66) of these mines confirmed an effect on at least one fish effect indicator (Figure 3). Sixty-four percent (28/44) of mines confirming effects observed at least one effect equal to or greater than the CES. This included 19 mines with effects equal to or greater than the CES in both studies and 9 mines with effects equal to or greater than the CES in one study and less than the CES in the other study used to confirm effects. Unconfirmed effects were observed by 29% (19/66) of mines and 3 (5%) mines confirmed an absence of effects on all fish indicators.
Figure 3. Fish effect categories for mines completing two or more studies
Description
Figure 3 is a pie chart illustrating effect categories for 66 mines completing two or more fish population biological monitoring studies. The effect categories are shown in number of mines. The four types of effect categories identified in the graph are confirmed effects equal to or greater than CES (28), confirmed effects less than CES (16), unconfirmed effects (19) and confirmed absence of effects (3).
The effect categories for each fish population indicator for the 66 mines having completed at least two fish population studies are shown in Figure 4. The lowest number of mines is found in the confirmed absence of effect category, followed by the confirmed effects and unconfirmed effects categories. The proportion of mines observing unconfirmed effects on a specific indicator ranged from 47 to 57%. Of the 44 mines observing confirmed effects, 36% confirmed effects on one indicator, 30% on two indicators, 13.5% on 3 indicators, 16% on four indicators and 4.5% on all indicators. It should be noted however, that some studies did not obtain sufficient data to assess all indicators.
For the indicators of survival, growth and body condition, the number of mines with confirmed effects less than the CES was similar to the number of mines with confirmed effects equal to or greater than the CES. Confirmed effects on reproduction and liver condition were more often equal to or greater than the CES. Depending on the indicator, for 55 to 60% of the mines that observed confirmed effects, survival, growth and liver condition were larger and reproduction and body condition were smaller in the area exposed to effluent compared to unexposed areas.
Figure 4. Effect categories for each fish population indicator for 66 mines completing two or more fish population studies
Description
Figure 4 is a bar chart illustrating the number, type and magnitude of effect indicators observed by 66 mines completing two or more fish population biological monitoring studies. The y-axis represents the number of mines and the x-axis represents the type and magnitude of the fish effects observed. The direction of the effect is denoted as > when exposure was greater than reference and < when exposure was less than reference. The 5 types of fish effect indicators includes: survival (7 confirmed absence of effect, 30 unconfirmed effect, 2 < and 6 > confirmed effect less than CES, 5 < and 4 > confirmed effect equal to or greater than CES); growth (4 confirmed absence of effect, 26 unconfirmed effect, 5 < and 5 > confirmed effect less than CES, 4 < and 7 > confirmed effect equal to or greater than CES); reproduction (6 confirmed absence of effect, 22 unconfirmed effects, 7 < and 6 > confirmed effect less than CES, 7 < and 6 > confirmed effect equal to or greater than CES); body condition (7 confirmed absence of effect, 33 unconfirmed effect, 7 < and 5 > confirmed effect less than CES, 9 < and 5 > confirmed effect equal to or greater than CES); liver condition (4 confirmed absence of effect, 28 unconfirmed effect, 1 < and 2> confirmed effect less than CES, 5 < and 7 > confirmed effect equal to or greater than CES).
Note: Some studies did not obtain sufficient data to assess all indicators. Effects are denoted as > when the indicator was larger in the exposure area relative to the reference area and denoted as < when the indicator was smaller in the exposure area relative to the reference area. The “confirmed effect less than CES” category includes mines with confirmed effects of unknown magnitude relative to the CES (5 for survival, 7 for growth and 3 for body condition). The “confirmed effect equal to or greater than CES” category includes mines with confirmed effects of variable magnitude between studies (5 for survival, 2 for growth, 9 for reproduction, 6 for body condition and 4 for liver condition).
A total of 39 mines completed a single study assessing effects on the fish population. Of these 39 mines, 95% observed effects and half of these mines observed at least one effect equal to or greater than the CES (Figure 5). One mine observed no statistically significant differences between their exposure and reference sites (referred to as an absence of effects) on all fish population indicators. Another mine observed an absence of effect on survival and body condition, but growth, reproduction and liver condition could not be assessed with the information obtained by the study.
Figure 5. Fish effect categories for mines completing a single study
Description
Figure 5 is a pie chart illustrating effect categories for 39 mines completing one fish population biological monitoring study. The effect categories are shown in number of mines. The three types of effect categories identified in the graphs are effects equal to or greater than CES (19), effects less than CES (18) and confirmed absence of effects (2).
Effect categories for each of the fish population indicators for the 39 mines having completed a single fish population study are shown in Figure 6. The proportion of mines that observed effects on survival or reproduction was 54 and 48%, respectively. For growth, liver condition and body condition, the proportion varied between 70 and 75%. For all indicators, the mines more often observed effects less than the CES than effects equal to or greater than the CES.
In the case of the mines that observed effects, four of the five fish population indicators were more often larger in the area exposed to effluent than in the reference area. The percentage of mines that observed effects for which the indicators were larger in the exposure area was as follows: 58% for survival, 56% for growth, 61% for body condition and 53% for liver condition. The percentage of mines that observed effects for which the indicators were smaller in the exposure area was 57% for reproduction.
Figure 6. Effect categories for each fish population indicator for 39 mines with a single completed fish population study
Description
Figure 6 is a bar chart illustrating the number, type and magnitude of effect indicators observed by 39 mines completing one fish population biological monitoring study. The y-axis represents the number of mines and the x-axis represents the type and magnitude of the fish effects observed. The direction of the effect is denoted as > when exposure was greater than reference and < when exposure was less than reference. The 5 types of fish effect indicators includes: survival (16 absence of effect, 6 < and 7 > effect less than CES, 2 < and 4 > effect equal to or greater than CES); growth (8 absence of effect, 7 < and 9 > effect less than CES, 3 < and 3 > effect equal to or greater than CES); reproduction (15 absence of effect, 6 < and 4 > effect less than CES, 2 < and 2 > effect equal to or greater than CES); body condition (10 absence of effect, 10 < and 10 > effect less than CES, 1 < and 7 > effect equal to or greater than CES); liver condition (8 absence of effect, 6 < and 5 > effect less than CES, 3 < and 5 > effect equal to or greater than CES).
Note: Some studies did not obtain sufficient data to assess all indicators. Effects are denoted as > when the indicator was larger in the exposure area relative to the reference area and denoted as < when the indicator was smaller in the exposure area relative to the reference area. The “effect less than CES” category includes effects of unknown magnitude relative to the CES (8 for survival, 11 for growth, 6 for reproduction, 11 for body condition and 4 for liver condition).
3.3 Effects on Fish Habitat
The indicators used to assess effects on fish habitat are total benthic invertebrate density, the evenness index, taxon richness and the similarity index (Bray-Curtis Index). Eighty-one mines completed two or more studies to assess effects on fish habitat, and 64% (52/81) of these mines confirmed an effect on at least one fish habitat indicator. One mine reported that all confirmed effects were less than the CES. Fifty-one mines reported that at least one effect was equal to or greater than the CES. This included 38 mines with effects equal to or greater than the CES in both studies used to confirm effects and 13 mines with effects equal to or greater than the CES in one study and less than the CES in the other study used to confirm effects. Unconfirmed effects were observed by 32% (26/81) of these mines and four percent (3/81) of mines confirmed an absence of effect on all four fish habitat indicators (Figure 7).
Figure 7. Fish habitat effect categories for mines completing two or more studies
Description
Figure 7 is a pie chart illustrating effect categories for 81 mines completing two or more benthic invertebrate community biological monitoring studies. The effect categories are shown in number of mines. The four types of effect categories identified in the graphs are confirmed effects equal to or greater than CES (51), confirmed effects less than CES (1), unconfirmed effects (26) and confirmed absence of effects (3).
The effect categories for each fish habitat indicator for the 81 mines having completed at least two fish habitat studies are shown in Figure 8. For density, taxon richness and evenness, the highest number of mines is found in the confirmed absence of effect category, followed by unconfirmed effects and confirmed effects. With regard to the similarity index, more mines observed confirmed effects than a confirmed absence of effects, and the proportion of mines observing unconfirmed effects was similar to the other three indicators. Confirmed effects on fish habitat were almost always equal to or greater than the CES.
Approximately half (27/52) of the mines with confirmed effects on fish habitat observed confirmed effects on two or more fish habitat indicators, and the other 25 mines observed a single confirmed effect on fish habitat. The similarity index (Bray-Curtis Index) was the single confirmed effect on fish habitat for 19 of these mines, 12 of which also observed confirmed effects on fish population indicators. The comparative analysis, described in section 2.3, confirmed that there were no observations of false positive effects resulting from the use of the methodology used in the Environmental Effects Monitoring technical guidance document (Environment Canada 2012a) to calculate the statistical significance of differences observed in the Bray-Curtis Index.
Most of the confirmed effects on taxon richness consisted of decreases observed in the area exposed to effluent, whereas the confirmed effects on evenness consisted of an equal number of indicator increases or decreases observed in the exposure area. The number of mines with confirmed increases in density in the area exposed to effluent was higher than the number of mines with confirmed decreases in density.
Figure 8. Effect categories for each fish habitat indicator for 81 mines completing two or more fish habitat studies
Description
Figure 8 is a bar chart illustrating the number, type and magnitude of effect indicators observed by 81 mines completing two or more benthic invertebrate community biological monitoring studies. The y-axis represents the number of mines and the x-axis represents the type and magnitude of the benthic effects observed. The direction of the effect is denoted as > when exposure was greater than reference and < when exposure was less than reference. The four types of benthic effect indicators includes: density (37 confirmed absence of effect, 28 unconfirmed effect, 0 confirmed effect less than CES, 5 < and 11 > confirmed effect equal to or greater than CES); taxon richness (38 confirmed absence of effect, 23 unconfirmed effect, 0 < and 2 > confirmed effect less than CES, 16 < and 2 > confirmed effect equal to or greater than CES); evenness index (36 confirmed absence of effect, 32 unconfirmed effects, 0 < and 1 > confirmed effect less than CES, 4 < and 4 > confirmed effect equal to or greater than CES); Bray-Curtis index (9 confirmed absence of effect, 27 unconfirmed effect, 3 confirmed effect less than CES, 42 confirmed effect equal to or greater than CES).
Note: Effects are denoted as > when the indicator was larger in the exposure area relative to the reference area and denoted as < when the indicator was smaller in the exposure area relative to the reference area, Similarity Index is neither smaller or larger, but denotes a non-directional degree of difference. The “confirmed effect equal to or greater than CES” category includes some mines with confirmed effects of variable magnitude between studies (4 for density, 6 for taxon richness, 1 for evenness and 14 for similarity). Four mines could not assess evenness.
Thirty-four mines completed a single study to assess effects on fish habitat and 82% (28/34) of these mines observed effects. Three quarters (21/28) of the mines with effects observed at least one effect equal to or greater than the CES. Six of the 34 mines (18%) observed an absence of effect on all fish habitat indicators (Figure 9).
Figure 9. Fish habitat effect categories for mines completing a single study
Description
Figure 9 is a pie chart illustrating effect categories for 34 mines completing one benthic invertebrate community biological monitoring study. The effect categories are shown in number of mines. The three types of effect categories identified in the graphs are effects equal to or greater than CES (21), effects less than CES (7) and confirmed absence of effects (6).
Effect categories for each of the fish habitat indicators for the 34 mines having completed a single fish habitat study are shown in Figure 10. Half of the mines observed an effect on density and 70% observed an effect on the similarity index. Effects on taxon richness and evenness were observed at just over a quarter of the mines.
The effects on density and taxon richness were most often found to be a reduction in the indicator in the exposure area compared to the reference area. For the evenness index, the number of mines with observed effects that showed lower values in the exposure area relative to the reference area was similar to the number of mines with observed effects that showed higher values in the exposure area relative to the reference area. Similarity index calculations produce a unidirectional measure of change in benthic invertebrate community structure.
Figure 10. Effect category for each fish habitat indicator for 34 mines with a single completed fish habitat study
Description
Figure 10 is a bar chart illustrating the number, type and magnitude of effect indicators observed by 34 mines completing one benthic invertebrate community biological monitoring study. The y-axis represents the number of mines and the x-axis represents the type and magnitude of the benthic effects observed. The direction of the effect is denoted as > when exposure was greater than reference and < when exposure was less than reference. The three types of benthic effect indicators includes: density (17 absence of effect, 6 < and 2 > effect less than CES, 6 < and 3 > effect equal to or greater than CES); taxon richness (25 absence of effect, 5 < and 1 > effect less than CES, 3 < and 0 > effect equal to or greater than CES); evenness index (24 absence of effect, 3 < and 1 > effect less than CES, 2 < and 3 > effect equal to or greater than CES); Bray-Curtis index (10 absence of effect, 5 effect less than CES, 19 effect equal to or greater than CES).
Note: Effects are denoted as > when the indicator was larger in the exposure area relative to the reference area and denoted as < when the indicator was smaller in the exposure area relative to the reference area, Similarity Index is neither smaller or larger, but denotes a non-directional degree of difference. Five mines conducted more than one benthic study but the results from only one study were usable. For one mine, the “effect less than CES” category for density, taxon richness and similarity includes effects of unknown magnitude relative to the CES. Evenness could not be assessed for one mine.
3.4 Effects on the Usability of Fisheries Resources
The potential effect of metal mining effluent on the usability of fisheries resources is assessed through a study measuring the concentration of mercury in fish tissue. A study is required when the concentration of mercury in final effluent is equal to or greater than 0.10 µg/L (MMER, Schedule 5, section 9).
Since 2002, 56 mines have conducted 67 studies of mercury concentrations in fish tissue. Two studies were not successful: one because the species tested in the exposure area was different than the species tested in the reference area, and another study, using caged bivalves, because the cages at the exposure site could not be relocated for recovery. Sixteen studies were conducted on a voluntary basis, given that the total mercury concentration in the effluent was less than 0.10 µg/L. The reasons for conducting a fish tissue study on a voluntary basis included: 1) exploring the historical mine-related influences on fish tissue mercury levels, 2) satisfying provincial requirements, 3) participating in joint studies organized by the Quebec Mining Association, and 4) proactively assessing potential current mine-related effects.
An “effect on fish tissue” is defined in the MMER as measurements of concentrations of total mercury that exceed 0.5 µg/g wet weight in fish tissue taken in an exposure area and that are statistically higher than the concentrations of total mercury in fish tissue taken in a reference area.
The mean total mercury concentration in fish was calculated using raw data on mercury concentrations in fish tissue that were submitted by mines electronically. These means were compared with the results reported in the study. If raw electronic data were not available, the means presented in the study reports were used. The statistical difference between the mean total mercury concentrations in fish tissue from the exposure area and reference area was determined by the mines and presented in the study reports. Mean total mercury concentrations in fish tissue obtained for the exposure and reference areas by each mine and the fish species tested are shown in Appendix D, Figures D1 to D3.
An effect on fish tissue, as defined in the MMER, was observed in one study (Figure 11). The mine in question reported that the fish tissue effect was caused by historical contamination present in the exposure area and was not due to current mine effluent.
Figure 11. Effect categories for 65 fish tissue studies conducted in each biological monitoring study period
Description
Figure 11 is a bar chart illustrating effect categories for 65 completed fish tissue studies. The y-axis represents the number of studies conducted and the x-axis represents the study period. In the first study period the effect categories include: no significant difference between reference and exposure (12), no effect exposure < reference (7), no effect exposure > reference and < 0.5 µg/g (3), effect exposure > reference and > 0.5 µg/g (1), statistical difference not determined (6). In the second study period the effect categories include: no significant difference between reference and exposure (9), no effect exposure < reference (9), no effect exposure > reference and < 0.5 µg/g (1), effect exposure > reference and > 0.5 µg/g (0), statistical difference not determined (5). In the third study period the effect categories include: no significant difference between reference and exposure (5), no effect exposure < reference (5), no effect exposure > reference and < 0.5 µg/g (1), effect exposure > reference and > 0.5 µg/g (0), statistical difference not determined (0). In the fourth study period the effect categories include: no significant difference between reference and exposure (1), no effect exposure < reference (0), no effect exposure > reference and < 0.5 µg/g (0), effect exposure > reference and > 0.5 µg/g (0), statistical difference not determined (0).
Note: Eleven studies did not determine the statistical difference between the two sampling areas because either the total mercury concentrations in fish tissue taken in the exposure area were lower than the concentrations in the reference area or the total mercury concentrations in effluent-exposed fish were lower than the MMER defined effect level.
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