2.7.5 Spatial and Temporal Variability in the Phytoplankton Community

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Spatial and temporal variation is inherent in plankton communities. However, sampling of phytoplankton is restricted to the photic zone; therefore, water depth should not be a confounding factor. Analysis of a sub-set of archived community composition samples and a more detailed data analysis has been proposed as part of the updated Plankton Special Effects Study (SES) in Section 5.

2.7.6 Chlorophyll a as an Indicator of the Phytoplankton Community

At this time, there is insufficient data to complete this evaluation for phytoplankton. Chlorophyll a can be used as a practical alternative; however, it varies seasonally and taxonomically (Wetzel 2001). Analysis of a sub-set of archived community composition samples and the assessment of the efficacy of chlorophyll a has been proposed as part of the updated Plankton Special Effects Study (SES) in Section 5.

Monitoring of periphyton and macrophytes was not included in the AEMP. In 1996, it was documented that Lac de Gras supported only marginal growth of macrophytes along the shoreline. Wave action and ice scour likely prevents macrophytes from establishing. For these same reasons, periphyton growth would likely be limited within the first few metres. Further rationale for not including periphyton monitoring is included in Section 5.

2.7.7 Suitability of Baseline Data for Establishing Baseline Conditions of the Phytoplankton Community

Power analysis completed on baseline data confirmed that these data had sufficient power to detect a significant difference and a relatively small sample size (i.e., 7 samples each a composite of two), would be required to detect a 10% difference between Lac de Gras and Lac de Sauvage (Table 2.7-8; Golder 1998). Wherever possible, sampling methods and locations have remained consistent over time, allowing continued comparison to baseline data. The analysis of archived community composition samples will provide additional information for confirming baseline conditions (see Section 5).

Table 2.7-8 Required Sample Size for Determination of Statistical Differences in Chlorophyll a Concentrations Between Lac de Gras and Lac du Sauvage

Estimated Sample Size Date LG (MSE) (based on % difference) 5% 10% 20% 50% 100% August 14 to 17, 1997 0.00049 24 7 3 1 1 September 2 to 9, 1997 0.00040 20 6 2 1 1 Source: Golder 1998. Notes: LG = Lac de Gras; MSE = Mean Square Error; % = percent.

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2.7.8 Minimum Acceptable Variation in the Phytoplankton Community

At this time, there is insufficient data to recommend minimum acceptable variation due to the natural variability characteristic of plankton communities. Analysis of a sub-set of archived community composition samples and a more detailed data analysis is proposed as part of the updated Plankton Special Effects Study (SES) in Section 5. A recommendation on the efficacy of the use of surrogate measures, such as chlorophyll a, is one objective of the Plankton SES.

2.8 ZOOPLANKTON COMMUNITY

Although this section is largely organized to reflect the corresponding section of the TOR, there are some differences in the organization and order of subsections to allow efficient presentation of information and to include all relevant information. Section 2.8.1 presents the information related to zooplankton baseline data as required by parts (a), (b), and (c) of TOR Section 2.8. Section 2.8.2 presents information related to the current AEMP data as required by part (a) of TOR Section 2.8. Section 2.8.3 to 2.8.6 presents information as required by parts (d), (e), (f), and (g), respectively, as required by TOR Section 2.8.

2.8.1 Zooplankton Baseline Data Collection and Data Quality

Baseline data for the zooplankton community was collected in the open water season of 1995, 1997, and 2000 (Table 2.8-1). All samples were analyzed, except taxonomy samples collected in 2000, which were archived.

Table 2.8-1 Zooplankton Baseline Data Collection

Year Under Ice Open Water Reference 1995 Mar 12-Mar 19 Jul 27 – Aug 4 Acres and Bryant (1996b) Sept 19 – 24 1997 July 21-28 Golder Associates (1998) Aug 14-18 Sept 1-12 2000 Sept 4-10 Diavik Diamond Mines Inc. (2001) a = Zooplankton taxonomy samples were not analyzed, but have been archived.

Eight stations were sampled during July, August, and September of 1997 to study the seasonal trend and variation in the zooplankton biomass and community composition (Golder 1998). Zooplankton samples were collected by towing a 76 µm plankton net vertically through the top 10 m of the water column. Duplicate samples, each comprised of three vertical tows, were collected and preserved for biomass determination. For taxonomic determination, five samples were collected, each from a separate vertical tow.

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Based on data from August 1997 (i.e. mid-summer), the zooplankton community in Lac de Gras consisted of the following 40 zooplankton taxa:

o Rotifer • Conochilus sp.; • Conochilus unicornis; • Kellicottia longispina; • Keratella cochlearis; • Keratella hiemalis; • Keratella quadrata; • Keratella sp.; and, • Polyarthra sp. o Copepod • Cyclops scutifer; • Leptodiaptomus ashlandi; • Mesocyclops sp.; • Heterocope septentrionalis; • Diaptomus species; • Copepod nauplii; • Immature calanoid; and, • Immature cyclopoid. o Cladoceran • Bosmina coregoni; • Bosmina longirostris; • Bosmina sp.; • Daphnia longiremis; • Daphnia middendorffiana; • Daphnia sp.; and, • Holopedium gibberum.

The zooplankton community composition was similar throughout the open water season. Rotifers dominated the zooplankton community (62.5% to 81.5%) (Table 2.8-2). Copepods were the next most dominant group, accounting for 12.9% to 35.3%. The dominant taxa were the rotifers, Conochilus unicornus and Kellicottia longispina (Figure 2.8-1).

Zooplankton biomass was low throughout the open water season (Golder 1998). Median concentrations ranged from 70.2 mg/m3 to 137.1 mg/m3. Variations were important among sampling months and stations within a month (Table 2.8-2). Stations WQ-06 and WQ-07 had the highest zooplankton biomass (Table 2.8-3).

Zooplankton biomass from 1995 to 2000 is summarized in Table 2.8-4. Median concentrations ranged from 32.7 mg/m3 at station BHP-S to 113.0 mg/m3 at station LDG43. LDG42 had the second highest biomass with 111.2 mg/m3.

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Table 2.8-2 Proportional Abundance of Zooplankton Taxa Collected in Lac de Gras, 1997

Major Taxonomic Group July August September (% Abundance) (% Abundance) (% Abundance) Rotatoria (Rotifers) 62.5 81.5 73.8 Cladocera (Cladocerans) 2.2 5.6 9.6 Copepoda (Copepods) 35.3 12.9 16.6 Total 100 100 100 Source: Golder 1998. Note: % = percentage.

Figure 2.8-1 Dominant Zooplankton Taxa, Lac de Gras August 1997

100%

80%

60% % ofTotal Taxa 40%

20%

0% WQ-05 WQ-06 WQ-13 WQ-14 WQ-10 Sampling Station

Holopedium gibberum Keratella cochlearis cochlearis Daphnia longiremis SARS Bosmina coregon Copepodites Cyclopoida Copepodites + adults Diaptomidae Kellicottia longispina longispina Conochilus unicornis Collotheca sp.

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Table 2.8-3 Open Water Zooplankton Biomass in Lac de Gras, 1997

Station Units Median 25 Percentile 75 Percentile n Near- Field WQ04 mg/m3 77.4 31.3 82.5 6 Mid-Field WQ01 mg/m3 70.2 57.0 87.1 6 WQ13 mg/m3 90.0 79.4 110.6 6 Far-Field WQ03 mg/m3 72.6 43.5 91.6 6 WQ05 mg/m3 89.0 31.2 109.2 6 WQ06 mg/m3 137.1 107.7 140.9 8 WQ07 mg/m3 113.5 105.3 116.9 15 WQ14 mg/m3 87.5 69.0 100.3 6 Source: Golder 1998. Notes: mg/m3 = milligram per cubic metre; n = sample size.

Table 2.8-4 Open Water Zooplankton Biomass in Lac de Gras, 1995 to 2000

Station Units Median 25th Percentile 75th Percentile n

Mid-field mg/m3 50.3 25.2 78.8 112 LDG-40 mg/m3 47.8 47.4 48.1 2 LDG-41 mg/m3 60.2 27.4 104.5 8 LDG-42 mg/m3 111.2 77.3 146.5 8 LDG-43 mg/m3 113 78.8 120.5 8 LDG-44 mg/m3 61.7 47.7 89.8 8 LDG-45(a) mg/m3 35.4 20.1 58 72 LDG-49 mg/m3 61.5 48.8 70.5 6 3 Far-field mg/m 37.1 18.3 62.2 115 LDG-48 mg/m3 49.5 40.5 61.5 6 LDG-46 mg/m3 63.5 56.3 78.3 6 BHP-S mg/m3 32.7 16.9 60.6 103 LDG - All Stations mg/m3 44.2 20.8 72.3 227

Source: DDMI March 2001. Notes: mg/m3 = milligrams per cubic meter; LDG = Lac de Gras; n = sample size a = LDG 45 baseline data were collected from BHP AEM sites M1 and M2. 2.8.2 Original AEMP Data

The original AEMP included annual collection of open water zooplankton samples at mid-field and far-field sites between 2001 and 2006. Zooplankton samples were collected by vertically towing a 76 µm plankton net through the top 10 m of the water column. Duplicate samples, each consisting of three vertical tows, were collected, preserved, and

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analyzed for total zooplankton biomass. Samples for zooplankton taxonomy analysis were collected and archived.

In 2003, DDMI identified an error in the laboratory analysis of the zooplankton biomass (i.e., incorrect sub-sampling of original samples) (DDMI March 2004); these data have not been included in this document. This error was corrected for subsequent analyses (DDMI March 2005b).

Based on visual inspection of the data, zooplankton biomass appears to have decreased over time (Table 2.8-5). In 2004, the mean absolute difference between duplicate zooplankton results indicated issues with repeatability of results, particularly at LDG 40 and LDG 44. In addition, the zooplankton biomass data collected by DDMI prior to 2005 trends opposite to BHPB data (DDMI March 2005b).

Table 2.8-5 Open Water Zooplankton Biomass in Lac de Gras, 2001 to 2006

Group Sampling Stations 2001 2002 2004 2005 2006 Mid-field LDG 40 69.72 23.63 217.13 12.00 15.26 (mg/m3) 65.85 42.64 194.55 0.01 22.99 LDG 41 50.80 62.08 182.82 8.82 17.70 49.01 38.58 201.20 8.07 12.41 LDG 42 69.86 36.13 899.04 14.10 9.83 61.51 21.93 260.80 13.02 11.19 LDG 43 64.29 28.82 242.09 10.92 13.29 72.69 33.77 218.83 15.19 11.80 LDG 44 49.06 5.71 170.07 10.04 15.26 43.68 63.73 176.04 23.06 17.77 LDG 45 62.08 73.25 283.04 24.28 12.68 53.11 35.61 328.82 21.22 16.48 LDG 49 34.08 18.07 146.54 3.73 11.19 29.42 12.83 n/a 5.36 10.92 Mid-field Median 57.31 34.69 217.13 11.46 12.99 Summary 75th Percentile 65.46 41.63 260.80 14.92 16.17 (mg/m3) 25th Percentile 49.02 22.36 182.82 8.26 11.34 n 14 14 13 14 14 Far-field LDG 46 37.92 54.15 265.34 7.73 8.21 (mg/m3) - 13.96 146.34 9.29 10.92 LDG 50 26.57 68.11 32.55 5.29 15.73 30.03 77.59 212.05 6.71 13.77 Far-field Median 26.57 13.4 30.09 57.3 12.34 Summary 75th Percentile 33.03 33.05 123.72 61.04 14.26 (mg/m3) 25th Percentile 18.11 5.59 22.86 8.12 10.24 n 21 22 11 10 4 Source = DDMI 2005b and unpublished data. Notes: mg/m3 = milligrams per cubic meter; n = sample size; - = no data available.

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2.8.3 Zooplankton Biomass as Indicator of Zooplankton Community Composition

At this time, there is insufficient data to complete this evaluation. Analysis of a sub-set of archived community composition samples and the assessment of the biomass-community composition relationship has been proposed as part of the updated Plankton Special Effects Study (SES) in Section 5.

2.8.4 Spatial and Temporal Variation in Zooplankton Community

Spatial and temporal variation is inherent in plankton communities. Zooplankton biomass samples are currently collected from within the photic zone. This design was to standardize the area of sampling between the phytoplankton and zooplankton communities. However, many zooplankton taxa migrate into deeper water during the day as a method of predator avoidance. As a result, restricting sampling of zooplankton within the photic zone may have resulted in an underestimate of zooplankton biomass.

2.8.5 Suitability of Data for Establishing Baseline Conditions

Power analysis on zooplankton baseline data indicated that the zooplankton biomass data were more variable than the phytoplankton biomass data, reflecting the well known patchiness of zooplankton. Consequently, much larger samples are required to detect a percent difference similar to that for phytoplankton biomass (Table 2.8-6). At best, a 50% change in zooplankton biomass could be detected with ten composite samples of three vertical tows (Golder 1998).

Table 2.8-6 Required Sample Size for the Determination of Statistical Differences Between Lac de Gras and Lac de Sauvage Plankton Communities

Estimated Sample Size Date LG (MSE) (based on % difference) 5% 10% 20% 50% 100% (August 14-17/97) 0.01286 602 159 44 10 4 (September 2-9/97) 0.00853 400 105 30 7 3 Note: % = percentage.

2.8.6 Minimum Acceptable Variation

At this time, there are insufficient data to recommend minimum acceptable variation due to the natural variability characteristic of plankton communities. Analysis of a sub-set of archived community composition samples and a more detailed data analysis are proposed as part of the updated Plankton Special Effects Study (SES) in Section 5. However, the archieved samples cannot provide a complete measure of variation since vertical variation

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was not fully captured by the sampling method. The use of community indices and other metrics will be examined as part of the SES.

2.9 BENTHIC INVERTEBRATE COMMUNITY

Although this section is largely organized to reflect the corresponding section of the TOR, there are some differences in the organization and order of subsections to allow efficient presentation of information and to include all relevant information. Additional sections to those specified in the TOR include Section 2.9.2 (Data Summary Methods) and Section 2.9.3 (Habitat Characteristics). Section 2.9.5 (Habitat Relationships) presents the information required by parts (d) and (e) of TOR Section 2.9, and is presented before the discussion of temporal/spatial variability and required sampling effort to provide the necessary background information. Part (f) of TOR Section 2.9 (minimum acceptable variation) is part of study design and is discussed in Section 4, based on results of analyses presented in this section.

2.9.1 Summary of Available Data and Data Quality

DDMI conducted baseline benthic invertebrate surveys in Lac de Gras in 1994, 1995 (Acres and Bryant 1996b), 1996 (Golder 1997g), and 1997 (Golder 1998), and has been monitoring benthic invertebrate communities annually since 2001 (DDMI 2002a, 2003, 2004, 2005c; the 2005 and 2006 data have not been reported to date but were included in this summary). The original AEMP study design (DDMI July 2001a) consists of sampling three replicate stations in each of three sampling areas designated as near-field, mid-field, and far-field, located at increasing distances from the mine-water discharge. Locations of these areas are as follows:

o Near-field area – about 1 km east of the mine-water discharge; o Mid-Field area – about 4 km east of the mine-water discharge; and, o Far-Field area – near the outlet of Lac de Gras to the Coppermine River.

Table 2.9-1 presents a summary of benthic invertebrate sampling programs carried out in Lac de Gras. All studies sampled during the fall, and the 1995 study also included summer sampling. Number and locations of stations have varied among years during the baseline period, but has been consistent since 2001. During each study, three to six samples were collected at each station using a 15-cm Ekman grab (bottom area: 0.0232 m2). Supporting data included water depth, sediment particle size (percentages of sand, silt and clay) and TOC.

Since 2001, the six samples collected at each station have been pooled to prepare a single composite sample, to reduce laboratory costs. Pooling of samples was based on the results of the 1996 baseline study (Golder 1997g), which concluded that collecting six samples at a station usually yields representative data from Lac de Gras. Additionally, it was recognized that individual stations would be used as the unit of replication in statistical

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analysis of the monitoring data, rather than individual samples, consistent with the data analysis procedure used in aquatic Environmental Effects Monitoring studies for pulp mills (EC 1998) and metal mines (EC 2002).

Benthic invertebrate samples were processed by different taxonomists during different years (Table 2.9-1). In the laboratory, invertebrates were removed from the samples and were identified to the lowest practical taxonomic level. Midges (Chironomidae) were identified to subfamily/tribe in 1994 and 1995 and to genus thereafter. Because of the low invertebrate abundances in the samples, subsampling was rarely done.

Table 2.9-1 Summary of Benthic Invertebrate Sampling Programs in Lac de Gras

Sub- No. of Screen samples Samples Sampling Year Stations Sampled Mesh Size Composited Taxonomist Reference per Device (µm) in the Station Field? 1994 B001 and B002 (=NF) 3 Ekman grab 425 No unknown (Acres ACRES 1995 (fall) International Corp.) 1995 LDG-1, LDG-2, LDG- 3 Ekman grab 425 No unknown (Acres ACRES 1995 (summer 3, LDG-4, LDG-5 International Corp.) and fall) (=NF), LDG-6, LDG- 7, LDG-8 (=MF), LDG-9 1996 Three stations at 3 Ekman grab 250 No D. Parker Golder 1997a (fall) each of N1, N2, N3, N4, N5, N6, N7 (=NF), N8, N9, N10, F14 (=MF), F15, F16 1997 (fall) Four stations at each 6 Ekman grab 250 No D. Parker Golder 1997b of F14 (=MF) and WQ14 (=FF) 2001 to Three stations at 6 Ekman grab 250 Yes 2001: Bio-Limno DDMI 2002, 2006 (fall) each of NF, MF and (re-identified by 2003, 2004 FF S. Kovats) (2005 and 2006 2002 to 2004: data have not S. Kovats been reported 2005 and 2006: to date) J. Zloty Notes: NF = Near-field; MF = Mid-field; FF = Far-field.

There were some differences in laboratory methods among studies, which reduce the comparability of data among years. In 1994 and 1995, benthic samples were screened using a 425 µm mesh sieve; during all other years, samples were screened using 250-µm mesh sieves. This difference can be expected to result in lower total numbers of invertebrates and different taxonomic composition in samples collected in 1994 and 1995 relative to subsequent years of monitoring. In addition, the following obvious differences in the 1996 to 2006 data resulted from the use of different taxonomists:

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o varying levels of identifications for Oligochaeta and Chironomidae among years; o absence of Harpacticoida from the 1996 data set; o low taxonomic richness and near-absence of Harpacticoida, Ostracoda, and Hydracarina from the 2001 data set; and, o varying proportions of Chironomidae left at the subfamily/tribe levels in different years.

Despite these differences, laboratory methods were reasonably similar to allow use of the 1996 to 2006 data in one analysis, provided that the above differences in taxonomy are taken into account. Due to the differences in mesh-size and the lowest level of midge taxonomy noted above, the 1994 and 1995 data are not comparable to the 1996 to 2006 data.

In addition to differences in laboratory methods, there are two factors that reduce among-year comparability of the data:

o Differences in station locations among studies: baseline studies sampled a larger number of stations than the subsequent AEMP. However, other than those located at or close to the near-field, mid-field, and far-field locations (identified in Table 2.9-1), each station was sampled only once during baseline programs, which does not allow an evaluation of year-to-year variation in areas other than near-field, mid-field, and far-field.

o Variation in number of samples collected at individual sites: three to six samples were collected at a station, which represents a reasonable effort in most lakes; however, collection of three samples may not result in representative data in Lac de Gras in some cases due to low density of benthic invertebrates.

o Depth variation: a large proportion of baseline samples were collected in shallower water than those collected during the AEMP.

Based on the information presented above, the data set selected for summarizing benthic invertebrate community data for Lac de Gras included the subset of the 1996 and 1997 baseline data collected at stations situated within or close to the near-field, mid-field, and far-field areas, and data collected in those same areas during the AEMP (2001 to 2006) (Figure 2.9-1). Although 1996 and 1997 stations were not positioned exactly at the AEMP sampling stations, it was assumed that they were reasonably close to be representative of those areas.

138 LAC DU SAUVAGE

FAR - FIELD AREA

LDG-FF WQ-14 DETAIL "A"

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D LDG-MF F14 c a

L LDG-NF n i

s N7 n o i t a S g n i l p m a S e t a r b e t r e v n I c i h SCALE: 2X t n e B

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w PROJECT No. 06-1328-001 SCALE AS SHOWN REV. 0 o l l DESIGN e REFERENCE

Y GIS JSB 15/02/07 \ s i UTM Zone 12, NAD 83. CHECK FIGURE: 2.9-1 g \ : REVIEW g Diavik Diamond Mines Inc. AEMP Design Document 2007

2.9.2 Data Summary Methods

Benthic invertebrate data were summarized as follows:

o total density (total number of organisms per square metre); o richness (total taxa at the lowest level of identification); o community composition as percentages of total density in major invertebrate groups; o densities of common invertebrate groups, defined as those accounting for >5% of the total density at a station; o dominance (percentage of the dominant taxon at a site); o Simpson’s diversity index (SDI); and, o evenness index.

For all years and stations selected for the summary, the above variables were summarized as the mean and standard error (SE) of the mean for each sampling area (near-field, mid-field, far-field) in each year. Spatial (among-area) and temporal (among-year) variations were illustrated as bar graphs of sampling area means and corresponding standard errors. Physical habitat data consisting of water depth, sediment particle size and TOC were also summarized as bar graphs. Relationships between habitat variables and biological variables were investigated by running Spearman rank correlations (Sokal and Rohlf 1995) and examining significant correlations as scatter-plots.

Baseline variation in benthic community variables among stations was estimated as 2 standard deviations (SD) of the mean, expressed as the percentage of the mean, based on 1996 and 1997 data and far-field area data (2001 to 2006). It was assumed that no mine related effects have occurred in the far-field area. Near-field and mid-field data collected during the AEMP were excluded from this analysis because of the possibility of mine-related effects.

Among-year baseline variation was expressed as the percent change in each benthic community variable from one year to the next (or one sampling program to the next). Data were grouped by water depth to minimize the effect of depth-variation on the estimates of among-year baseline variation.

Effort required to characterize the benthic community was estimated based on an analysis of the number of samples required from a station based on 1996 data (Golder 1997g) and generic power analysis results provided by Environment Canada (2002) for metal mining EEM benthic invertebrate surveys.

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2.9.3 Habitat Characteristics

Benthic invertebrate samples were collected at water depths typically ranging from 15 m to 25 m, with the exception of the far-field area, where depth was considerably greater since 2004 (Figure 2.9-2; habitat data are provided in Appendix 2-9, Table I-2, for all years and sampling areas). Particle size distribution of bottom sediments was similar during 2001 to 2006, when sediments were dominated by silt in all sampling areas (Figure 2.9-3). Sand content was higher in 1996 and 1997, which may reflect differences in station locations relative to AEMP stations, or analysis of sediments by different laboratories. Sediment TOC content in the near-field and mid-field areas was similar and low in all years (Figure 2.9-4). Far-field area TOC values were about two times higher than near-field and mid-field values since 2001. This difference was consistent among areas despite the variation in water depth in the far-field area.

The differences in habitat features among sampling areas and years were sufficiently large to influence benthic invertebrate community characteristics. In particular, the higher water depth and sediment TOC content in the far-field area indicate that this area may not be a suitable reference area for evaluating mine-related effects on benthic invertebrates.

Figure 2.9-2 Variation in Water Depth among Years and Sampling Areas in Lac de Gras, 1996 to 2006

40 NF

35 MF FF

Mean (±1 SE) WaterDepth (m) 10

0 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Year

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Figure 2.9-3 Variation in Sediment Particle Size Distribution among Years and Sampling Areas in Lac de Gras, 1996 to 2006

100%

80%

60%

40% % Composition

20%

0% 1997 - FF 2001 - FF 2002 - FF 2003 - FF 2004 - FF 2005 - FF 2006 - FF 1996 - NF 2001 - NF 2002 - NF 2003 - NF 2004 - NF 2005 - NF 2006 - NF 1996 - MF 1997 - MF 2001 - MF 2002 - MF 2003 - MF 2004 - MF 2005 - MF 2006 - MF Year - Area

Sand Silt Clay Silt+Clay

Figure 2.9-4 Variation in Sediment Total Organic Carbon among Years and Sampling Areas in Lac de Gras, 1996 to 2006

10 NF 9 MF FF 8

4 Mean (±1 SE) TOC(%) 3

0 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Year

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2.9.4 Benthic Community Characteristics

2.9.4.1 Species List and Community Composition

A taxon list based on all previous surveys of Lac de Gras is provided in Appendix II.4 (Table II.4-1). To the end of 2006, 15 families and 29 genera have been reported from Lac de Gras. Of the 15 families, three are primarily riverine (Baetidae, Lepidostomatidae, Capniidae), suggesting that some of the invertebrates sampled in the lake originated in nearby streams. The majority (36) of the 49 genera belong to the midge family (Chironomidae), consistent with the numerical dominance of the benthic community by midges reported by all surveys.

The benthic community of Lac de Gras between 1996 and 2006 was characterized by low and highly variable total invertebrate density, ranging from a few hundred to about 10,000 organisms/m2 (Figure 2.9.5; means and SEs for benthic community variables are provided in Appendix II.4, Table II.4-3, for all years and sampling areas). Richness was in the low to moderate range, with 10 taxa to 20 taxa recorded in most sampling areas and years, and was less variable than total density, both among stations and years.

Dominant benthic invertebrate groups included midges, harpacticoid copepods (Harpacticoida), roundworms (Nematoda), fingernail clams (Sphaeriidae) and ostracods (Ostracoda) (Figure 2.9-6). The first four of these groups typically accounted for 80% or more of total density, with the exception of the far-field area, where ostracods have also been abundant since 2003.

Densities of the five dominant invertebrate groups were highly variable among sampling areas and years (Figures 2.9-7 and 2.9-8). Among-area variation reflects habitat variation (especially water depth and sediment TOC) and, potentially, the effect of the Mine in the near-field and mid-field areas. Among-year variation was also considerable, ranging up to two orders of magnitude for Harpacticoida in the near-field area. The general order in degree of variability among years was: Chironomidae < Ostracoda < Sphaeriidae < Nematoda < Harpacticoida.

Community indices were more stable, both among sampling areas and years (Figure 2.9-8). Mean dominance (i.e., the percentage of total density represented by the most abundant taxon) within a sampling area was typically between 20 and 40%, with the exception of 2001 (near-field and mid-field) and 2003 (near-field). In both 2001 and 2003, the midge genus Heterotrissocladius was unusually abundant compared to other invertebrates, which resulted in the high dominance values.

SDI values were between 0.7 and 0.9, indicating moderate to high diversity, with the exception of 2001 (all areas) and 2003 (near-field only) when SDI values were lower (Figure 2.9-8). Evenness was more variable than SDI, especially among areas, with near-field and mid-field values mostly between 0.2 and 0.4, and far-field values usually between 0.4 and 0.6.

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Figure 2.9-5 Variation in Total Invertebrate Density and Richness among Years and Sampling Areas in Lac de Gras, 1996 to 2006

Total Invertebrate Density 12,000 NF 10,000 MF

f FF

8,000 2

6,000

4,000 Organisms/m

Mean (±1 SE) Number o Number SE) (±1 Mean 2,000

0 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Year

Richness 25

20 MF a FF

10 Numberof Taxa / Are 5

0 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Year

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Figure 2.9-6 Variation in Benthic Invertebrate Community Composition among Years and Sampling Areas in Lac de Gras, 1996 to 2006

Densities 10,000 9,000 8,000

) 7,000 2 6,000

5,000 4,000

Density (no./m 3,000 2,000 1,000

0 1997 - FF 2001 - FF 2002 - FF 2003 - FF 2004 - FF 2005 - FF 2006 - FF 1996 - NF 2001 - NF 2002 - NF 2003 - NF 2004 - NF 2005 - NF 2006 - NF 1996 - MF 1997 - MF 2001 - MF 2002 - MF 2003 - MF 2004 - MF 2005 - MF 2006 - MF Year - Area

Percentages 100%

80%

60%

40%

% of TotalDensity 20%

0% 2006 - FF 2005 - FF 2004 - FF 2003 - FF 2002 - FF 2001 - FF 1997 - FF 2006 - NF 2005 - NF 2004 - NF 2003 - NF 2002 - NF 2001 - NF 1996 - NF 2006 -MF 2005 -MF 2004 -MF 2003 -MF 2002 -MF 2001 -MF 1996 -MF 1997 -MF Year - Area Chironomidae Harpacticoida Nematoda Sphaeriidae Ostracoda Oligochaeta Hydracarina Other

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Figure 2.9-7 Variation in Densities of Nematoda, Sphaeriidae, Ostracoda and Harpacticoida among Years and Sampling Areas in Lac de Gras, 1996 to 2006

Nematoda Sphaeriidae 2,500 700 2

2 NF NF 600

MF sms/m MF 2,000 FF FF 500

1,500 400

300 1,000

200

500 100 Mean (±1 SE) Number of Organi Mean (±1 SE) Number of organisms/m 0 0 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Year Year

Ostracoda Harpacticoida 1,400 5,000 2 2 NF 4,500 NF 1,200 MF 4,000 MF FF FF 1,000 3,500

3,000 800 2,500

600 2,000

1,500 400 1,000 200 500 Mean (±1 SE)Number ofOrganisms/m Mean (±1 SE)Number ofOrganisms/m 0 0 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Year Year

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Figure 2.9-8 Variation in Chironomidae Density, Dominance, SDI and Evenness among Years and Sampling Areas in Lac de Gras, 1996 to 2006

Chironomidae Density Dominance 5,000 80 2 4,500 NF 70 NF 4,000 MF MF 60 FF FF 3,500

3,000 50

2,500 40

2,000 30 1,500 20

1,000 Mean (±1SE) Dominance(%) 10

Mean (±1 SE) Numberof Organisms/m 500

0 0 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Year Year

SDI Evenness 1.0 1.0

0.9 0.9 NF NF MF 0.8 MF 0.8 FF 0.7 FF 0.7

0.6 0.6

0.5 0.5

0.4 0.4 Mean(±1 SE) SDI 0.3 0.3 Mean (±1 SE) Evenness

0.2 0.2

0.1 0.1

0.0 0.0 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Year Year

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2.9.5 Habitat Relationships

Results of correlations between benthic community variables and habitat variables suggested that overall, the variation in community structure in Lac de Gras reflects habitat variation. Total density, richness and abundances of two dominant invertebrate groups were significantly negatively correlated with water depth (Table 2.9-2). Midge density was also correlated with sediment clay content and TOC. The direction of the correlations with depth were consistent with the general decline in invertebrate abundance and richness with increasing water depth in lakes.

Scatter-plots of significant depth relationships (Figure 2.9-9) revealed that an analysis of mine-related effects based on available monitoring data could be confounded by depth variation. The highest abundances observed in 2004 and 2006 were in the near-field area (e.g., Figures 2.9-5 and 2.9-7), where water depth was also the lowest. In addition, water depth and exposure to the effluent were intermediate at stations in the near-field area, whereas depth was usually the highest and effluent exposure the lowest in the far-field area. Thus, the reason for the sharp decline in invertebrate abundance between 15 m and 20 m cannot be attributed to either potential cause.

Table 2.9-2 Spearman Rank Correlations Between Benthic Community Variables and Habitat Variables

Habitat Variable Variable Water Depth % Sand % Silt % Clay TOC

Total Density and Richness Total density -0.51 0.04 0.17 -0.30 -0.26 Richness -0.41 0.07 0.17 -0.17 0.03 Dominant Invertebrates Nematoda -0.25 0.27 -0.09 -0.11 -0.07 Sphaeriidae -0.19 -0.22 0.20 0.15 -0.09 Ostracoda 0.13 0.05 0.01 -0.14 -0.09 Harpacticoida -0.53 0.35 0.03 -0.38 0.07 Chironomidae -0.64 -0.04 0.27 -0.44 -0.41 Community Indices Dominance 0.05 -0.31 0.33 -0.04 -0.12 Simpson's Diversity Index -0.12 0.36 -0.32 0.07 0.16 Evenness 0.31 0.21 -0.40 0.21 0.19 Note: Significant correlation coefficients are bolded (P<0.05; Bonferroni adjustment applied); TOC = total organic carbon

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Figure 2.9-9 Relationships between Water Depth and Benthic Community Variables

Total Density Richness 14,000 30

NF 12,000 NF 25 MF MF FF 10,000 FF

) 20 2 8,000 15 6,000 Total TaxaTotal

Density (no/m 10 4,000

2,000 5

0 0 10 15 20 25 30 35 40 10 15 20 25 30 35 40 Water Depth (m) Water Depth (m)

Harpacticoida Density Chironomidae Density 7,000 5,000

4,500 NF NF 6,000 MF MF 4,000 FF 5,000 FF 3,500 ) ) 2 2 3,000 4,000 2,500 3,000 2,000 Density (no/m Density (no/m 2,000 1,500 1,000 1,000 500

0 0 10 15 20 25 30 35 40 10 15 20 25 30 35 40 Water Depth (m) Water Depth (m)

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2.9.6 Spatial and Temporal Variation in Benthic Community Variables and Required Sampling Effort

Spatial (among-station) variation in benthic community variables under baseline conditions was estimated as 2 SD of the mean, expressed as the percentage of the mean, using data collected during baseline years (1996 and 1997) and in the far-field area where exposure to mine effluent is expected to be minimal. Based on eight years of data, the median among-site variation for density variables ranged from 53% to 131%, whereas maximum variation was greater than 300% for some variables (Table 2.9-3). As expected, variation in richness was lower, with a median and maximum of 24% and 67%, respectively. The SDI was the least variable, with a maximum variation of only 37%. The among-station variation in evenness and dominance was intermediate between those in richness and density variables.

Temporal (among-year) variation in benthic community variables under baseline conditions was estimated as the percent change in the mean value for a sampling area from one year to the next (or one sampling program to the next), after grouping data in the far-field area by water depth to minimize the influence of depth variation. Results of this analysis showed that year-to-year variation in benthic community characteristics can be very large and inconsistent among years (Table 2.9-4). For example, the % change in total density ranged from only 14% in the far-field area between 2005 and 2006 to over 1000% between 2001 and 2003. Excluding % change values on either side of the year 2001, when laboratory methods were most different from those employed in other years, results in considerably lower estimates of among-year variation for total density, richness, densities of Sphaeriidae and Chironomidae, SDI and evenness, close to the ranges described above for among-site variation. However, year-to-year variation in densities of other dominant invertebrates remained high (i.e., up to 1008% for Nematoda) even after this operation.

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Table 2.9-3 Among-station Variation in Benthic Invertebrate Community Variables during Baseline Years (1996, 1997) and in the AEMP Reference Area (Far-Field)

2 Standard Deviations Expressed as the Percentage of the Mean Number Water Total Nematoda Harpacticoida Ostracoda Sphaeriidae Chironomidae Simpson's Year Area of Depth Richness Density Density Density Density Density Density Diversity Evenness (%) Dominance (%) Stations (m) (%) (%) (%) (%) (%) (%) (%) Index (%) 1996 NF 3 17-21.6 58 28.6 44 - 173 63 83 3 19 9 1996 MF 3 19.2-22.5 62 30.8 53 - 99 20 75 13 49 79 1997 FF 4 17 77 22 52 93 131 84 76 5 27 19 1997 MF 4 21 8 25 27 52 118 70 48 5 24 42 2001 FF 3 23.7 148 66.7 - - - 164 156 18 37 39 2002 FF 3 18 58 12.5 53 84 291 66 66 6 27 29 2003 FF 3 25.3 31 10.5 34 18 68 137 42 7 57 80 2004 FF 3 37.6 78 16.4 74 74 91 80 98 4 42 24 2005 FF 3 34 206 20.0 198 346 346 103 106 37 124 120 2006 FF 3 35 79 36.7 346 - 150 169 146 18 67 64 Median 70 24 53 79 131 82 79 7 40 40 Minimum 8 11 27 18 68 20 42 3 19 9 Maximum 206 67 346 346 346 169 156 37 124 120 Note: - = not applicable; taxon was not enumerated; % = percent; NF = near-field; MF = mid-field; and FF = far-field.

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Table 2.9-4 Among-year Variation in Benthic Invertebrate Community Variables during Baseline Years (1996, 1997) and in the AEMP Reference Area (Far-Field)

MF (19.2 - 22.5 m depth) FF (17 - 25.3 m depth) FF (34 - 37.6 m depth) Variable % % % % % % 1996 Change 1997 1997 Change 2001 Change 2002 Change 2003 2004 Change 2005 Change 2006 Total Density and Richness Total density (no./m2) 1,538 45% 2,236 3,754 -96% 142 1246% 1,906 49% 2,834 2,657 -87% 350 -14% 302 Richness (total taxa) 13 31% 17 22 -73% 6 167% 16 19% 19 19 -46% 10 -17% 8 Dominant Invertebrates Nematoda (no./m2) 268 85% 496 339 - 0(a) - 31 1008% 346 718 -98% 17 -86% 2 Harpacticoida (no./m2) 0(a) - 194 1,324 - 0(a) - 70 359% 319 125 -98% 2 -100% 0 Ostracoda (no./m2) 33 591% 231 181 - 0(a) - 43 928% 444 912 -83% 154 -66% 53 Sphaeriidae (no./m2) 143 15% 165 206 -74% 53 168% 142 76% 250 202 -75% 50 81% 91 Chironomidae (no./m2) 922 12% 1,034 1,627 -95% 84 1691% 1,505 -18% 1,236 444 -80% 89 19% 106 Community Indices Simpson's Diversity Index 0.841 3% 0.863 0.841 -15% 0.712 18% 0.840 6% 0.888 0.795 -5% 0.756 -3% 0.737 Evenness 0.411 -15% 0.350 0.231 168% 0.621 -37% 0.388 6% 0.410 0.238 126% 0.536 -8% 0.491 Dominance (%) 28.3 -8% 25.9 34.7 18% 41.1 -27% 30.0 -29% 21.2 33.5 12% 37.6 9% 41.1 Notes: no/m2 = number of organisms per square metre; - = not applicable; % = percent; MF = mid-field; FF = far-field. a = taxon was not enumerated.

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An analysis of sampling effort required to collect representative data at individual stations in Lac de Gras was undertaken as part of the 1996 baseline program (Golder 1997g). Results of graphical analysis of the variability among closely-spaced samples showed that for total density, richness and densities of common invertebrates, the variation among samples tended to stabilize at six samples per station in shallow and moderately deep areas. However, for densities of individual taxa, the variation among samples remained higher than the degree of variation usually considered reasonable for benthic invertebrate data (i.e., an SE that is ≤20% of the mean [or %SE ≤20]; Elliott 1971), suggesting that reaching this goal may not be possible for benthic invertebrate densities other than total density and richness in Lac de Gras.

To confirm that six samples per station yield representative data, within station variation was evaluated for total density, richness and densities of dominant invertebrates based on the 1997 data collected by Golder (1998), which consist of six individually analyzed samples collected at eight stations (four in each of mid-field and far-field areas). Results of this analysis were consistent with those of Golder (1997g), and indicated that six samples per station were in most cases adequate to achieve a %SE of 20 for total density, richness and density of the most dominant invertebrate group (midges) (Table 2.9-5). For densities of individual taxa, %SE values were consistently below 40 for Sphaeriidae, but were greater than 40 for two to three of the eight stations. For commonly used benthic community indices (domainance, SDI, eveness) %SE values were below 20, with only a single exception, which was below 30. Based on these results and those of the 1996 analysis, which indicated little gain in precision beyond six samples, six samples per station represents a reasonable minimum number of samples to obtain representative data during future surveys.

The sampling effort required within a sampling area (i.e., number of stations) can be estimated based on power analysis, and therefore depends on the parameters required by power analysis (i.e., α, β, critical effect size, estimate of among-station variation). Setting the critical effect size to 2 SD of the reference area mean is recommended for aquatic EEM to evaluate the effects of pulp mills and metal mines (EC 1998, 2002) and represents a reasonable approach to evaluate mine-related effects as well. Using this approach, the power analysis becomes generic, with results that have been summarized by Environment Canada in the technical guidance document for EEM (EC 2002). Results of this power analysis are used in Section 4 to estimate the sampling effort required for monitoring the effects of the mine on the benthic invertebrate community of Lac de Gras.

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Table 2.9-5 Within-Station Variation in Benthic Invertebrate Community Variables during the 1997 Baseline Program

Area Total Density Richness Nematoda Ostracoda Sphaeriidae Harpacticoida Chironomidae Dominance SDI Evenness and Station Mean ± SE %SE Mean ± SE %SE Mean ± SE %SE Mean ± SE %SE Mean ± SE %SE Mean ± SE %SE Mean ± SE %SE Mean ± SE %SE Mean ± SE %SE Mean ± SE %SE Far-field Area FF1 2,064 ± 406 20 10.5 ± 0.9 9 308 ± 120 39 79 ± 48 60 93 ± 26 28 695 ± 132 19 824 ± 158 19 36 ± 5 15 0.80 ± 0.04 5 0.44 ± 0.06 14 FF2 4,343 ± 814 19 14.8 ± 1.1 8 423 ± 238 56 129 ± 99 76 287 ± 72 25 1,390 ± 498 36 2014 ± 363 18 30 ± 7 25 0.83 ± 0.06 7 0.43 ± 0.07 17 FF3 3,182 ± 579 18 13.3 ± 0.9 7 229 ± 69 30 165 ± 23 14 186 ± 48 26 1068 ± 260 24 1476 ± 297 20 34 ± 4 12 0.83 ± 0.02 3 0.40 ± 0.04 9 FF4 5,425 ± 1374 25 12.7 ± 0.8 6 394 ± 138 35 351 ± 123 35 258 ± 79 31 2143 ± 443 21 2193 ± 618 28 43 ± 4 9 0.77 ± 0.03 4 0.29 ± 0.02 6 Mid-field Area MF1 2,107 ± 267 13 10.5 ± 0.4 4 559 ± 173 31 158 ± 61 39 237 ± 62 26 222 ± 56 25 781 ± 161 21 26 ± 5 18 0.84 ± 0.02 3 0.57 ± 0.08 14 MF2 2,243 ± 262 12 9.7 ± 0.6 6 459 ± 128 28 423 ± 46 11 100 ± 33 33 129 ± 37 29 1046 ± 191 18 28 ± 3 12 0.83 ± 0.02 2 0.53 ± 0.04 7 MF3 2,301 ± 733 32 10 ± 0.8 8 545 ± 280 51 229 ± 74 32 179 ± 71 40 244 ± 125 51 939 ± 241 26 33 ± 3 8 0.82 ± 0.02 2 0.50 ± 0.05 9 MF4 2,293 ± 406 18 8.8 ± 1 12 423 ± 154 36 115 ± 47 41 143 ± 36 25 179 ± 91 51 1369 ± 242 18 34 ± 3 9 0.79 ± 0.03 4 0.48 ± 0.05 10 Notes: SE = standard error; %SE = standard error expressed as the percentage of the mean; %SE values >20% are bolded; %SE values >40% are bolded and shaded; FF – far-field; and MF = mid-field.

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2.10 FISH COMMUNITY

The following sections provide the fish community information as outlined in Section 2.10 of the final Terms of Reference (WLWB and Gartner Lee 2007). The information was collated from a number of published and unpublished sources, and builds on the information provided in the environmental baseline and EA for the Mine, submitted in 1998 (DDMI 1998a, 1998b).

As per Section 2.0 of the final Terms of Reference (WLWB and Gartner Lee Ltd 2007), the information provided in the following sections was drawn from:

o studies done to inform the Comprehensive Study Report and EA predictions (pre-1998); o studies done between the EA submission and the start of construction (1998-1999); and, o any studies done since 1999 that can be shown to be free of influence of Mine activity, which were completed as a Special Effects Study (SES) under the terms of the first Water License or which can be used to assess variability in sampling.

2.10.1 Documented Fish Species

Studies of the fish community in Lac de Gras include four fish surveys conducted in 1995 and 1996 in the Mine site area and throughout Lac de Gras (Acres and Bryant 1996b; Golder 1997h, 1997i, DDMI 1998a). The Mine site area is referred to as the “intensive study area” in the Integrated Environmental and Socio-economic Baseline Report (DDMI 1998a). The locations of the 1995 and 1996 fish surveys are shown in Figure 2.10-1. Fish surveys conducted in 1996 included an assessment of the fish community in Lac du Sauvage in 1996. The results of the Lac du Sauvage survey are not included in this report. Additional fisheries studies in Lac du Gras include an assessment of slimy sculpin (Cottus cognatus) collected from east island in 2004 (Gray et al. 2005). Information from the east island study is incorporated in the following sections.

Lac de Gras supports a stable, slow-growing community of coldwater fish, characteristic of a cold, ultra-oligotrophic lake and similar to other un-exploited Arctic lakes (Hobbie 1973). Despite the low productivity of the lake and its ultra-oligotrophic status, the biomass of fish is higher than that of similar lakes (McCart and Den Beste 1979). The higher biomass is largely due to the longevity of the species present, especially lake trout, which commonly exceed 30 years of age (McCart and Den Beste 1979). Therefore, the total biomass of all fish present in Lac de Gras represents the incremental accumulation of many years of low annual production. As a result of the low productivity, many fish in Arctic lakes, including Lac de Gras (Golder Associates 1997i), mature at an advanced age relative to individuals of the same species found in temperate lakes (McCart and Den Beste 1979). The low productivity and slower growth also result in lower reproductive rates: adult fish may spawn only every second or third year once they reach maturity (Scott and Crossman 1998).

155 FISH SURVEYS SITES, LAC DE GRAS 1995-1996

FIGURE: 2.10-1 Diavik Diamond Mines Inc. AEMP Design Document 2007

Nine fish species were captured and identified in Lac de Gras between 1995 and 2004 (Table 2.10-1). Based on fish surveys conducted in 1995 and 1996, the fish community in the area of Lac de Gras near the Mine site (i.e., the intensive study area) includes Arctic grayling (Thymallus arcticus), burbot (Lota lota), cisco (Coregonus artedii), lake trout (Salvelinus namaycush), lake whitefish (Coregonus clupeaformis), longnose sucker (Catostomus catostomus), round whitefish (Prosopium cylindraceum) and slimy sculpin (Acres and Bryant 1996b; Golder 1997h, 1997i). Burbot, lake trout, ninespine stickleback (Pungitius pungitius) and slimy sculpin were captured during the slimy sculpin assessment conducted near the east island in 2004 (Gray et al. 2005).

Table 2.10-1 Fish Species Collected in Lac de Gras

Common Name Scientific Name Arctic grayling Thymallus arcticus burbot Lota lota cisco Coregonus artedii lake trout Salvelinus namaycush lake whitefish Coregonus clupeaformis longnose sucker Catostomus catostomus ninespine stickleback Pungitius pungitius round whitefish Prosopium cylindraceum slimy sculpin Cottus cognatus Source: DDMI 1998b

Based on catch records from 1996, cisco and lake trout were abundant in Lac de Gras. Density of round whitefish appeared to be lower than that for lake trout or cisco. Arctic grayling may have been present in higher numbers than the catch records indicated. Arctic grayling tend to reside near the mouths of tributaries, which were not sampled during the baseline field studies (Golder 1997i). Densities of burbot and longnose sucker were extremely low. One slimy sculpin was captured near the shoreline of the east island in the summer of 1996. Northern pike were not captured from Lac de Gras, which may be indicative of the virtual absence of macrophytes, a requisite component of northern pike habitat.

The following section provides life history and ecological information for the nine fish species that are known to be present in Lac de Gras. Information specific to Lac de Gras fish populations is provided where available.

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2.10.2 Life History and Ecology of Documented Fish Species

2.10.2.1 Arctic Grayling

Arctic grayling can be found in lakes and streams throughout the mainland portions of the NWT, although the species is absent from the arctic islands (McCart and Den Beste 1979; Scott and Crossman 1998). Growth of Arctic grayling in the NWT is relatively slow with mature individuals seldom exceeding 500 mm in fork length (McCart and Den Beste 1979). Individuals generally mature in 6 to 9 years (Scott and Crossman 1998). Maximum ages for most populations are in the mid-teens but a few grayling have been aged at 20 years or more (McCart and Den Beste 1979). Juvenile Arctic grayling feed primarily on zooplankton, whereas adults consume a broad assortment of invertebrates, including terrestrial insects obtained at the surface of the water (Scott and Crossman 1998).

Arctic grayling typically spawn in small tributary streams during peak spring flows, just after ice break-up. The eggs develop and hatch quickly (approximately 8 to 14 days) in the same streams in which they were deposited. Shoreline habitats in lakes play a limited role in providing nursery habitat for Arctic grayling. Whenever possible, juvenile grayling frequent streams until flows become too low for them to use this habitat. When forced to move into lakes, juvenile grayling stay close to the mouth of streams (pers. obs. R.P. Schryer 1996). These areas are most often composed of boulder or a mixture of boulder and sand situated in shallow water.

2.10.2.2 Burbot

Burbot typically occurs in deep-water lakes throughout the continental portions of the NWT, but they may also occur in rivers, small streams, and low lying ponds. (Richardson et al. 2001). Burbot exhibit both lacustrine and riverine life history types within the NWT freshwater populations can be separated into lacustrine and adfluvial.

Burbot spawn under the ice at night between November and May (Richardson et al. 2001). Local timing of spawning is associated with water temperatures which are usually between 0.6°C and 1.7°C. Burbot are broadcast spawners, typically spawning in shallow water over sand, gravel or rubble substrates at a depth of 0.5 m to 3.0 m. Egg incubation is dependent on water temperature, and varies from three weeks to three months. Upon hatching sac fry are found primarily in the pelagic zone and congregate over sand and rubble substrates. Young-of-the-year burbot become benthic littoral feeders when they reach the fingerling stage between 20 mm and 40 mm in length. This change in habitat is accompanied by a transition from a crepuscular to nocturnal activity pattern. Once nocturnal, young burbot seek suitable shelter in shallow water during the daytime under physical structures such as boulders, cobble, logs, or within submergent vegetation, and remain inactive unless disturbed. Juveniles are typically found over rock and gravel bottoms along rocky shorelines. Generally, burbot reach sexual maturity between three and four years of age, with males usually reaching sexual maturity a year or two before

158 Diavik Diamond Mines Inc. AEMP Design Document 2007 females. As with juvenile burbot, adults are found over boulder, rubble, cobble, and sand substrates.

Burbot are sensitive to sub-surface illumination and seek shelter under stones, roots, and amongst aquatic plants during the day. While the burbot is considered to be a sedentary fish, extensive migrations over 400 km have been observed in the NWT. Northern populations of burbot appear to live longer and reach greater size than other populations, with the largest known fish being caught in Great Slave Lake, weighing 18.5 pounds with a fork length of 38.3 inches (Richardson et al. 2001). Adult burbot are primarily piscivorous feeding on ciscoes, cottids, whitefish, sticklebacks, and trout-perch.

2.10.2.3 Cisco

Cisco, also known as lake herring, are found in lakes across the NWT east of the Mackenzie River (McCart and Den Beste 1979; Scott and Crossman 1998). They are an open water species, usually forming large schools in mid-water depths (Scott and Crossman 1998). Cisco are commonly plankton feeders, occasionally feeding on some aquatic and terrestrial insects (McCart and Den Beste 1979). They play an important role in the food chain because they prey on plankton and are preyed on by larger piscivorous fish (McCart and Den Beste 1979). In particular, cisco are a preferred food item for lake trout (Scott and Crossman 1998). The largest cisco recorded from Great Slave Lake, NWT, weighed 2.5 kg and was 572 mm long (Scott and Crossman 1998). In general, males and females grow at the same rate, although females tend to live longer and may therefore reach a larger size (Scott and Crossman 1998).

Cisco spawn in the late fall, after the round whitefish and usually just before freeze-up (Scott and Crossman 1998; R. P. Schryer per. obs. 1996). Water temperatures observed during spawning range from 3.3oC to 5oC. The range of spawning depths is recorded at 2.0 m to 64.0 m (Scott and Crossman 1998), but occurs frequently on the shallower edge of this range. Substrates selected for spawning range from gravel to boulder (depending on availability) and should contain sufficient crevices to allow the eggs to be protected from predators. Usually, a hard or stony bottom is selected (Scott and Crossman 1998). As with the lake trout and round whitefish, unsuitable spawning habitats include open areas of bedrock that do not provide cover for the eggs, areas where the bottom is covered by organic matter or silt, and areas where water levels fluctuate to the point where eggs are directly exposed to air.

The requirements for cisco nursery and rearing habitats are similar to those of lake trout and round whitefish. Developing cisco embryos require adequate water circulation in an area that does not freeze over winter. Cisco fry are presumed to move from the nursery areas soon after spawning and form aggregate schools along steep shores or shallow sheltered waters in the lake.

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2.10.2.4 Lake Trout

Lake trout are found in deep lakes and occasionally in rivers throughout the mainland portions of the NWT and several of the arctic islands (McCart and Den Beste 1979). They achieve the largest size and are among the longest-lived (30+ years) of any freshwater fish species in the NWT (McCart and Den Beste 1979). Juvenile lake trout generally consume a wide range of aquatic dipterans, crustaceans and small fish, while adults predominantly prey on fish, including cisco, whitefish, sculpin, longnose sucker and juvenile lake trout (McCart and Den Beste 1979; Scott and Crossman 1998). Many populations of lake trout in the North have a majority of old, mature fish (10+ years) with mean lengths of 500 mm to 600 mm (Johnson 1972; Johnson 1976).

Northern lake trout usually spawn only in alternate years after reaching maturity and some only every third year (Falk et al. 1973, 1974 in McCart and Den Beste 1979). Therefore, in any year, at least one-half of the adult population consists of non-spawning (i.e., resting) individuals.

Spawning by lake trout in the NWT generally occurs in late September or in early October. Spawning can occur in water as deep as 55 m but the average depth ranges from 2 m to 6 m (Martin 1955, in Machniak 1975). To survive, eggs must be placed by the females in water deep enough to avoid freezing during the winter. As well, water levels cannot fluctuate to the point where the eggs are exposed to air (Machniak 1975).

Substrates used by lake trout for spawning are usually large boulders with large interstitial spaces mixed with some gravel (Marcus et al. 1984). The spaces between the rocks must be small enough to prevent predators from reaching the eggs (Machniak 1975), but large enough for water circulation to maintain adequate oxygen levels through the winter incubation period (Marcus et al. 1984). Lake trout have been observed to prefer angular versus smooth rocks (Marcus et al. 1984), presumably because of the greater depth and size of the interstitial spaces. Open areas of bedrock are unsuitable since they provide no cover for the eggs. The substrate must also have low levels of silt and organic matter or be subject to enough wave action to keep fine materials from smothering the eggs.

The habitat requirements of juvenile lake trout in arctic lakes are poorly understood. To survive, developing lake trout embryos must be in an area with adequate water circulation that does not freeze over winter. Fry move from the nursery areas to the deeper waters of the lake within a month of hatching (DeRoche 1969; in Bronte et al. 1995).

2.10.2.5 Lake Whitefish

Lake whitefish are commonly found in lakes throughout the NWT to a northern limit on Banks Island (Richardson et al. 2001). Lake whitefish are known to exhibit lacustrine, adfluvial, and anadromous life history types. Lacustrine populations have been noted to occur as two separate forms, normal and dwarf. However, there is no distinction in the literature of differential habitat use between the two forms.

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Freshwater resident lake whitefish may spawn from late summer to November or December. Individuals may only spawn every second or third year. They are known to spawn in both lakes and rivers over a variety of substrates, from large boulders to gravel and occasionally sand (Richardson et al. 2001). Although lake whitefish appear to avoid soft bottomed substrates when spawning, several authors have reported spawning in areas with silt substrates and emergent vegetation (Richardson et al. 2001). Spawning usually takes place in shallow water areas <5.0 m deep. Eggs are released over the substrate and settle in crevices and interstices, where they incubate for several months hatching sometime from March to May. Young lake whitefish are commonly found at the surface in shallow water areas <1 m within the general vicinity of the spawning area. Within shallow water zones, young lake whitefish are most commonly found in areas with boulder, cobble, and sand substrates in association with emergent vegetation and woody debris. As water temperatures warm, young move to deeper waters (3 m to 15 m) later in the summer. As with young lake trout, juveniles are most often found over boulder, cobble, and gravel substrates in association with vegetation and woody debris. In Great Slave and Great Bear lakes about half of both sexes mature in their eighth year.

Adult lake whitefish leave spawning grounds shortly after spawning, returning to deepwater habitat to overwinter. Lake whitefish are frequently found at depths >10 m for most of the year and have been found at depths in excess of 100 m. Lake whitefish may be found over boulder, gravel, cobble, sand, and clay substrates; however, they generally do not show a preference for substrate type. In addition they are primarily bottom dwelling, although they may be found in the pelagic zone of lakes. Lake whitefish have been reported to make marked onshore movements into shallow water habitats at night possibly to feed. Lake whitefish are bottom feeders and feed on snails, clams, chironomid larvae, and small fishes.

2.10.2.6 Longnose Sucker

The longnose sucker is common throughout the NWT and occur in freshwater lakes, rivers and streams (Richardson et al. 2001). The longnose sucker is known to exhibit lacustrine, adfluvial and riverine life history types.

Longnose suckers spawn in the spring shortly after melting of ice cover on lakes, from April to June. Longnose suckers spawn primarily in rivers but may spawn in the shallows of lakes. In lakes, spawning usually takes place at depths of 15 cm to 30 cm, along rocky wave-swept shorelines, over gravel and sand substrates. Eggs are adhesive and are broadcast over gravel and sand substrates, incubating from 11 to 15 days before hatching. Young remain in gravel for one to two weeks before emerging. Young frequent shallow areas of lakes often in association with vegetation and sandy substrates. Correspondingly, juveniles have also been shown to inhabit shallow weedy areas. Longnose suckers spawn between 5 and 15 years of age, with males starting a year or two earlier than the females (Richardson et al. 2001).

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The longnose sucker inhabits waters at depths that range from 1 m to 24 m, and have been found at 183 m (Richardson et al. 2001). Longnose sucker from Great Slave Lake feed mostly on amphipods, chironomids, midge larvae, caddis fly larvae, and sphaeriid clams.

2.10.2.7 Ninespine Stickleback

The ninespine stickleback is distributed throughout the NWT in rivers, lakes, slow streams, and tundra ponds. The ninespine stickleback is known to exhibit lacustrine, riverine, and andromous life history types (Richardson et al. 2001).

Spawning usually occurs in relatively shallow water from May to late July. Males typically build their nests amongst weeds in densely vegetated areas, 10 cm 15 cm off the bottom or occasionally in contact with the bottom. Nests are constructed from aquatic vegetation and debris bound together by a threadlike kidney secretion. Males may also nest in burrows constructed in muddy organic bottoms or under and between rocks along wave swept lake shores. Females are enticed into the nest, after they deposit 20 eggs to 30 eggs, the male then enters the nest and fertilizes the eggs, and chases the female away. Eggs incubate for four to seven days before hatching, upon which time the young are moved into a nursery area, which the male constructs from nest building material just above the nest.

Young remain in the nursery until they become free swimming at which time they disperse into shallow water areas amongst vegetation, moving to deepwater areas in the fall to overwinter. Ninespine sticklebacks usually mature in their first year, and have a life expectancy of about three and a half years. Although adult sticklebacks are found in association with shallow water, dense vegetation, and are tolerant of low oxygen concentration, they may also frequent open water areas over sand and gravel beaches with sparse vegetation or deep waters. Ninespine stickleback feed primarily on aquatic insects, chironomid larvae, small crustaceans, mollusks, cladocerans, and other zooplankton.

2.10.2.8 Round Whitefish

Round whitefish are found across the NWT, excluding the Arctic islands. Round whitefish consume a variety of benthic invertebrates that live attached to rocks on the lake bottom and shoreline. Consequently, shorelines with rocky substrates, which provide cover for benthic invertebrates, are preferred foraging habitat. Round whitefish are also suspected of feeding on the eggs of other fish, including lake trout. Maximum lengths of round whitefish are estimated at approximately 550 mm (Scott and Crossman 1998).

Round whitefish spawn in the late fall in the gravely shallows of lakes, at river mouths or occasionally in rivers (Scott and Crossman 1998; Harper 1948). Water temperatures observed during spawning range from 4.5oC to 6oC. The range of spawning depths is 4.0 m to 16.0 m. Substrates selected for spawning range from cobble to gravel depending

162 Diavik Diamond Mines Inc. AEMP Design Document 2007 on availability. Usually, a hard or stony bottom is selected (Scott and Crossman 1998). Preferred spawning habitat includes areas with clean, gravel/cobble substrates that contain sufficient crevices to allow eggs to be protected from predators. Unsuitable spawning habitats are similar to those of lake trout and cisco, including open areas of bedrock that do not provide cover for the eggs or areas where the bottom is covered by organic matter and/or silt.

As with lake trout, developing round whitefish embryos must be in an area with adequate water circulation that does not freeze over winter. Water levels cannot fluctuate to the point where the eggs are exposed to air. Fry are presumed to move from the nursery areas soon after spawning and form aggregate schools along steep shores or shallow waters in the lake.

2.10.2.9 Slimy Sculpin

Slimy sculpin are small-bodied, benthic fish that are widely distributed throughout Canada (Scott and Crossman 1998). Slimy sculpin feed primarily on aquatic invertebrates; they can reach a maximum length of approximately 13 cm and have a life span of five to six years (Van Vliet 1964). Sculpin spawn in spring under bolder-cobble substrates; they can reach sexual maturity at age one, but body size appears to be the determinant of maturity (Van Vliet 1964). During the spawning season, male slimy sculpin maintain and defend territories where multiple females deposit egg masses (Mousseau and Collins 1987; Gray 2003). In southern region, sculpin spawned at water temperatures between 6ºC and 10ºC (Gray 2003; Scott and Crossman 1998). Slimy sculpin exhibit relatively low mobility (Gray 2003; Galloway et al. 2003).

2.10.3 Age and Size Relationships for Major Fish Species

Section 2.10 of the final Terms of Reference (WLWB and Gartner Lee 2007) indicated that information on age and size relationships is required for any “major fish species (lake trout/whitefish/grayling) and for any proposed ‘sentinel’ indicators (e.g., sculpin)”. Therefore, the following section provides information on age and size relationships for:

o the four fish species (Arctic grayling, cisco, lake trout, round whitefish) that are known to be present in Lac de Gras and were identified in the EA as sentinel species; and, o slimy sculpin, which has been designated as sentinel species for assessment and monitoring purposes.

Arctic grayling, cisco, lake trout and round whitefish were identified as the four major fish species in the regional study area because of their positions in the food chain, importance to traditional and sports fishing, and sensitivity to chemicals/minerals in the environment. Slimy sculpin was identified as a sentinel species based on its use as a small-bodied sentinel species in other assessment and monitoring programs within Canada. Information specific to Lac de Gras fish populations is provided where available.

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Weight and fork length were measured from lake trout, round whitefish, cisco, and Arctic grayling captured in 1995 and 1996 (Acres and Bryant 1996b; Golder 1997h, 1997i). Age was measured from fish collected in summer and fall 1996. For fall 1996, lake trout was the only species targeted; information on weight, length, and age was available for that sole species (Golder 1997h).

Slimy sculpin collected in 2004 were mainly captured by electrofishing (Gray et al. 2005). Sculpin caught on August 18 (A154 dike location) and August 19 (REF 1 location), 2004 were measured for length and weight. Twenty adult sculpin from each site were sacrificed for metal and metallothionein analysis.

2.10.3.1 Arctic Grayling

Few Arctic grayling were captured in 1995 (total of 4) compared to 1996 (total of 41). All Arctic grayling caught in 1995 were captured near to east island, between the east and west island, or in a bay east of east island. However, all Arctic grayling were captured in tributary streams of Lac de Gras in summer of 1996. Arctic grayling sampled in 1995 is difficult to interpret because of the small sample size (Table 2.10-2).

In 1996, a narrow range of ages was observed in the Arctic grayling sampled during the spawning run near east island (Figure 2.10-2) (Golder 1997i). For example, the ages ranged between two and seven years of age in Lac de Gras. The majority of male and female Arctic grayling were found to be five, six, or seven years old.

More male Arctic grayling were sampled in 1996 than females or grayling of unknown sex type (Table 2.10-2). The females caught in Lac de Gras were heavier on average than male (Table 2.10-2). Overall, the male and female Arctic grayling had average condition factor values greater than 1.0. The female condition factor was slightly higher than the male.

Growth curves for Arctic grayling (Figure 2.10-3) present the relationship between length and age.

2.10.3.2 Cisco

Cisco are a relatively short-lived species compared to lake trout and round whitefish. For example, cisco captured near east island in Lac de Gras during fall 1995 ranged from 2 to 9 years of age (Figure 2.10-4) (Acres and Bryant 1996b). Ages six and seven were the dominant age classes. Growth curves for cisco are presented in Figure 2.10-5.

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Table 2.10-2 Size, Condition, and Sex Ratio for Arctic Grayling collected in Lac de Gras in Summer and Fall 1995 and 1996 near east island(a)

Mean Fork Mean Sample Size(b) Mean Weight Season Sex Length Condition Sex Ratio (n) g mm Factor (K) Summer Male 2 367.5 650 1.24 0.7 1995 Female 0 - - - - Immature 1 165 40 0.89 0.3 Fall Male 1 420 1100 1.48 1 1995 Female 0 - - - - Immature 0 - - - - Summer Male 25 396.28 805.8 1.2 0.6 1996 Female 12 409.42 890.8 1.29 0.3 Immature 4 164.25 33.8 0.86 0.1 Source: Acres and Bryant 1996b; Golder 1997i. Notes: n = sample size; mm = millimetres; g = grams; K = Condition factor; - = not applicable. a = In the intensive area as defined in the 1998 EA (DDMI 1998a). b = Sample sizes for 1995 data were calculated from total sample sizes and sex ratios.

165 Males in Lac de Gras (1996) Unknown in Lac de Gras (1996)

75 80

40 Frequency (%) Frequency (%) Frequency

0 0 2 3 4 5 6 7 1 2 3 4 Age Age Total number of Arctic grayling for Lac de Gras = 25 Total number of Arctic grayling for Lac de Gras = 4

Female in Lac de Gras (1996)

50 Frequency (%) Frequency

0 5 6 7

Total number of Arctic grayling for Lac de Gras = 12 Age

AGE DISTRIBUTION OF ARCTIC GRAYLING IN LAC DE GRAS

SOURCES : FIGURE: Golder 1997q 2.10-2 Diavik Diamond Mines Inc. AEMP Design Document 2007

Figure 2.10-3 Growth Curves of Arctic Grayling in Lac de Gras

Males in Lac de Gras (1996)

450 ) 400

SEM 350 300 250 200 150 100 50 Mean Length(mm 0 234567 Age (years) Total number of Arctic grayling for Lac de Gras = 25

Females in Lac de Gras (1996) 425 ) 420

SEM 415 410 405 400 395 390 385 380 Mean Length (mm 375 567 Age (years) Total number of Arctic grayling for Lac de Gras = 12

Unknown sex in Lac de Gras (1996) 200 180

SEM) 160 140 120 100 80 60 40 20

Mean Length (mm 0 123

Age (years) Total number of Arctic grayling for Lac de Gras = 4

Note: SEM = Standard error of the mean

167 Sex not Recorded Lac de Gras (1995) Females in Lac de Gras (1996)

40 50

45 35

40 30 35

25 30

20 25

Frequency (%) Frequency 20 Frequency (%) Frequency 15 15 10 10

5 5

0 0 2 3 4 5 6 7 8 9 5 6 7 8 Age Age Total number of cisco for Lac de Gras = 137 Total number of cisco for Lac de Gras = 13

Males in Lac de Gras (1996) Unknown sex in Lac de Gras (1996)

60 70

55 65 60 50 55 45 50 40 45

35 40

30 35

25 30 Frequency (%) Frequency Frequency (%) Frequency 25 20 20 15 15 10 10

5 5

0 0 5 6 7 8 1 2 3 4 5 6 7 Age Age Total number of cisco for Lac de Gras = 14 Total number of cisco for Lac de Gras = 81

AGE DISTRIBUTION OF CISCO IN LAC DE GRAS

SOURCES : Acres and Bryant 1996c FIGURE: Golder 1997q 2.10-4 Diavik Diamond Mines Inc. AEMP Design Document 2007

Figure 2.10-5 Growth Curves of Cisco in Lac de Gras

Males in Lac de Gras (1996)

500 450 400 SEM) 350 300 250 200 150 100 50 Mean Length(mm 0 5678

Total number of cisco for Lac de Gras = 14 Age (years)

Females in Lac de Gras (1996)

350 300

SEM) 250 200 150

100

50 Mean Length(mm 0 5678

Total number of cisco for Lac de Gras = 13 Age (years)

Unknown sex in Lac de Gras (1996)

260

210

SEM) 160

110

10 Mean Length (mm -40 1234567

Age (years) Total number of cisco for Lac de Gras = 81

Note: SEM = Standard error of the mean

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In 1996, relatively few age classes of cisco were sampled near east island in Lac de Gras, with ages ranging from five to eight years for both males and females (Figure 2.10-4) (Golder 1997i). The predominant age of both males and females in Lac de Gras was seven years of age. The majority of the “maturity unknown” cisco sampled in the intensive study area were two years old, although ages one through seven were represented.

The parameters measured in 1995 and 1996 had similar averages between males and females. The average lengths of male and female cisco were very similar in Lac de Gras as shown in Table 2.10-3. Average weight tended to increase from summer 1995 to summer 1996 for both males and females. The condition factors of males and females from both years were greater than 1.0 with the highest K in summer 1996 (Table 2.10-3). In 1996, a high number of cisco of unknown sex were caught in Lac de Gras (n = 81). These immature cisco showed large ranges in weights and condition factors (range in weight: 10 g to 181 g; range in K: 0.49 to 1.45).

2.10.3.3 Lake Trout

Lake trout exhibited the widest range of ages and were the most long-lived species of the four sentinel species (Lake trout, round whitefish, cisco and Arctic grayling) collected in Lac de Gras in 1995-96. In 1995, lake trout captured in the intensive study area of Lac de Gras ranged in age from 2 to 33 years (Figure 2.10-6). Two “peaks” in age frequency were observed, one at 6 to 8 years of age, and one at 14 to 16 years of age (Acres and Bryant 1996b). In 1996, ages for lake trout from the intensive study area of Lac de Gras ranged from 2 to 24 years (Figure 2.10-6) (Golder 1997i). The most frequently occurring ages for male lake trout were 8 and 11 years of age, although the numbers in a given age class were, in general, quite evenly distributed between 4 and 21 years of age. Female lake trout were slightly younger than the males with age 6 having the greatest frequency of occurrence. The majority of the lake trout sampled in 1996 whose sexual maturity was unknown had between 5 and 18 years old, with the most frequent age being 13 years old.

The average weights were similar between male and female lake trout sampled from Lac de Gras in 1995. Also, the male and female lake trout sampled in Lac de Gras in fall 1995 were heavier on average than those sampled in summer (Table 2.10-4). This difference may be explained by slightly different sampling techniques used in summer versus fall and the spawning condition of lake trout in fall, which is usually associated with greater weight.

Similarly, male and female lake trout collected in summer 1996 were similar in size (Table 2.10-4). In fall 1996, female lake trout were slightly longer and heavier than males. The average lengths of adult lake trout in 1996 were similar within the intensive (around east island) and extensive (in Lac de Gras but outside of the intensive area) study areas of Lac de Gras (DDMI 1998a).

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Table 2.10-3 Size, Condition and Sex Ratio for Cisco Collected in Lac de Gras in Summer and Fall 1995 and 1996 Near East Island(a)

Mean Fork Mean Sample Size(b) Mean Weight Season Sex Length Condition Sex Ratio (n) g mm Factor (K) Summer Male 43 250.5 197.5 1.25 0.6 1995 Female 21 225.6 210.7 1.23 0.3 Immature 7 151 47.5 0.81 0.1 Fall Male 60 262.6 213.9 1.18 0.3 1995 Female 79 265.5 224 1.19 0.4 Immature 60 123.6 18.3 0.94 0.3 Summer Male 14 260.64 242.21 1.35 0.13 1996 Female 13 260.54 271.31 1.48 0.12 Immature 81 141.38 30.87 1.02 0.75 Source: Acres and Bryant 1996b; Golder 1997i Note: n = sample size; mm = millimetres; g = grams; K = Condition factor. a = In the intensive area as defined in the 1998 EA (DDMI 1998a) b = Sample sizes for 1995 data were calculated from total sample sizes and sex ratios

Table 2.10-4 Size, Condition, and Sex Ratio for Lake Trout Collected in Lac de Gras in Summer and Fall 1995 and 1996 Near East Island(a)

Mean Fork Mean Sample Size(b) Mean Weight Season Sex Length Condition Sex Ratio (n) g mm Factor (K) Summer Male 79 507.8 1982.4 1.17 0.5 1995 Female 64 517.2 2098.3 1.1 0.4 Immature 16 202.4 116.8 0.93 0.1 Fall Male 55 533.4 2193.6 1.24 0.3 1995 Female 56 551.8 2497 1.24 0.3 Immature 74 208.6 122 1.04 0.4 Summer Male 39 484.41 1844.95 1.29 0.4 1996 Female 27 485.93 1880.19 1.21 0.28 Immature 31 588.32 2567.17 1.18 0.32 Fall Male 37 593 2784 1.16 0.34 1996 Female 33 619 3261 1.14 0.3 Immature 39 425 1294 1.13 0.36 Source: Acres and Bryant 1996b; Golder 1997h, 1997i Note: n = sample size; mm = millimetres; g = grams; K = Condition factor. a = In the intensive area as defined in the 1998 EA (DDMI 1998a) b = Sample sizes for 1995 data were calculated from total sample sizes and sex ratios.

171 Sex not Recorded Lac de Gras (1995) Female in Lac de Gras (1996)

15 20

10 14

10 Frequency (%) Frequency

Frequency (%) Frequency 8 5

2 0 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 0 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Age Total number of lake trout for Lac de Gras = 178 Total number of lake trout for Lac de Gras = 27 Age

Male in Lac de Gras (1996) Unknown Sex in Lac de Gras (1996)

16 20

14 18

16 12 14 10 12

8 10 Frequency (%) Frequency

6 (%) Frequency 8

6 4 4 2 2

0 0 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Age Age Total number of lake trout for Lac de Gras = 39 Total number of lake trout for Lac de Gras = 54

AGE DISTRIBUTION OF LAKE TROUT IN LAC DE GRAS

SOURCES : Acres and Bryant 1996c FIGURE: Golder 1997q 2.10-6 Diavik Diamond Mines Inc. AEMP Design Document 2007

Male and female lake trout from both years had condition factors slightly greater than 1 indicating good general health. In 1995, condition factors were higher in the fall than in the summer reflecting pre-spawning conditions at the sampling time. In 1996, condition factors were lower in fall although more than 50% of the fish were pre-spawning or ripe (Golder 1997h). Growth curves for lake trout are presented in Figure 2.10-7.

2.10.3.4 Round Whitefish

Round whitefish in Lac de Gras were relatively long-lived, although not as long-lived as lake trout. In general, there was no clear difference in age between male and female round whitefish in Lac de Gras. Round whitefish captured in Lac de Gras during 1995 were between 3 and 21 years old (Acres and Bryant 1996b). No 8, 17 and 18 years old fish were captured in 1995 (Figure 2.10-8). The most frequent age groups captured in descending order were 3, 13, 6 and 12 years of age (Acres and Bryant 1996b).

Round whitefish captured near east island in Lac de Gras during the 1996 survey had a wide range of ages (6 to 17 years) (Figure 2.10-8). The most common age of male round whitefish sampled was 11 years old. No male round whitefish captured in Lac de Gras were below the age of 11 years in 1996. Eleven years of age was the most frequent age group in female round whitefish collected from Lac de Gras in 1996 (Figure 2.10-8).

Males captured in the summer 1995 were smaller than female in length and weight (Table 2.10-5). The average condition factor for male of summer 1995 also reflects this difference (K = 0.93 compared to K=1.34 for female). These males were the only adult fish sampled with an average condition factor of less than 1.0. In fall 1995, male and female had similar size and condition factor.

Male round whitefish captured in summer 1996 were slightly longer and heavier than the females (Table 2.10-5). However, the average condition factor values determined for round whitefish were slightly lower in the males than the females during that same year (Table 2.10-5). Growth curves for round whitefish are presented in Figure 2.10-9.

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Figure 2.10-7 Growth Curves of Lake Trout in Lac de Gras

Males in Lac de Gras (1996)

800 700 SEM) 600 500 400 300 200 100 Mean Length (mm 0 23456789101112131415161718192021222324 Age (years) Total number of lake trout for Lac de Gras = 39

Females in Lac de Gras (1996) 800 700

SEM) 600 500 400 300 200 100 Mean Length (mm 0 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Age (years) Total number of lake trout for Lac de Gras = 27

Unknown sex in Lac de Gras (1996)

900 800 700 SEM) 600

500

400

300 200

Mean Length (mm 100 0 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Age (years) Total number of lake trout for Lac de Gras = 54

Note: SEM = Standard error of the mean

174 Sex not Recorded Lac de Gras (1995) Females in Lac de Gras (1996)

20 25

20 15

Frequency (%) 10 Frequency (%) Frequency

5 5

0 0 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 6 7 8 9 10 11 12 13 14 15 16 Age Age Total number of round whitefish for Lac de Gras = 176 Total number of round whitefish for Lac de Gras = 13

Males in Lac de Gras (1996)

Frequency(%) 15

0 11 12 13 14 15 16 17 Age Total number of round whitefish for Lac de Gras = 10

AGE DISTRIBUTION OF ROUND WHITEFISH IN LAC DE GRAS

SOURCES : Acres and Bryant 1996c FIGURE: Golder 1997q 2.10-8 Diavik Diamond Mines Inc. AEMP Design Document 2007

Table 2.10-5 Size, Condition, and Sex Ratio for Round Whitefish collected in Lac de Gras in Summer and Fall 1995 and 1996 near east island(a)

Mean Fork Mean Sample Size(b) Mean Weight Season Sex Length Condition Sex Ratio (n) g mm Factor (K) Summer Male 19 335 615.4 0.93 0.3 1995 Female 13 413.7 1147.8 1.34 0.2 Immature 32 165.8 38.1 0.57 0.5 Fall Male 12 423.7 1097.3 1.26 0.3 1995 Female 17 411 1062 1.29 0.4 Immature 13 151.1 23.5 0.54 0.3 Summer Male 10 447.3 1062.5 1.17 0.38 1996 Female 14 417.5 975.36 1.24 0.54 Immature 2 115.5 26.5 2.01 0.08 Source: Acres and Bryant 1996b; Golder 1997i Note: n = sample size; mm = millimetres; g = grams; K = Condition factor. a = In the intensive area as defined in the 1998 EA (DDMI 1998a) b = Sample sizes for 1995 data were calculated from total sample sizes and sex ratios

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Figure 2.10-9 Growth Curves of Round Whitefish in Lac de Gras

Males in Lac de Gras (1996)

500 450 400 SEM) 350 300 250 200 150 100 50 Mean Length (mm 0 11 12 13 14 15 16 17 Age (years) Total number of round w hitefish for Lac de Gras = 10

Females in Lac de Gras (1996)

600

500 SEM) 400

300

200

100 Mean Length (mm 0 6 7 8 9 10 11 12 13 14 15 16 Age (years)

Total number of round w hitefish for Lac de Gras = 13

Note: SEM = Standard error of the mean

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2.10.3.5 Slimy Sculpin

Slimy Sculpin were collected at three sites in Lac de Gras during August 2004: south side A154 dike; REF1 (future A21 site); and REF2 (north of west access to airstrip). However, length, weight, and condition factors were only reported for the first two sites (Gray et al. 2005). A strong age 1+ (last year’s YOY age class; first peak in length frequency distribution) existed at both the A154 dike site and the reference site (REF1) (Figure 2.10-10). No significant differences in length, condition factor, and adjusted condition factor existed between sites (Table 2.10-6). However, the sculpin collected at REF1 were significantly heavier than sculpin collected from the A154 dike site (Gray et al. 2005).

Table 2.10-6 Summary of Slimy Sculpin Sacrificed for Chemistry Analysis (mean ± standard error)

Site N Length (mm) Weight (g) Condition factor(a) Adjusted condition factor(b) A154 20 61.2 ± 1.5 2.07 ± 0.16 0.87 ± 0.02 0.74 ± 0.01 REF1 20 65.8 ± 1.9 2.68 + 0.23 0.91 ± 0.03 0.72 + 0.02 Source: Golder 1997i; Gray et al. 2005 Notes: N = sample size; mm = millimetres; g = grams a = Condition factor was calculated as 100000 * body weight (g)/length(mm)3 b = adjusted condition factor was 100000 *carcass weight/length3 (carcass weight = body weight-(liver+gonad+gut+ligula).

2.10.4 Habitat Mapping

Figure 2.6-3 is the shoreline habitat key map, which summarizes information from 15 more detailed habitat maps. Figures 2.6-4 to 2.6-18 present the more detailed maps of Lac de Gras. Additional information on the shoreline description can be found in Section 2.1 Physical Environment. Figures 2.6-19 to 2.6-23 presents the habitat maps of Lac de Gras shoals.

2.10.5 Spawning Areas

The utility of each type of habitat present in Lac de Gras was assessed for each of nine resident fish species and four life stages (i.e., spawning, nursery, rearing, and foraging)(DDMI 1998a). Sheltered rearing habitat for juveniles of some species was found to be limiting in Lac de Gras relative to habitat needed during other life stages. This section presents the spawning characteristics and locations for the five species identified as the major and sentinel species for this monitoring program (i.e., lake trout, round whitefish, cisco, Arctic grayling, and slimy sculpin).

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Figure 2.10-10 Length-Frequency Distribution of Slimy Sculpin

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2.10.5.1 Arctic Grayling Spawning Habitat

When ice is first breaking up and water temperatures are between 7oC to 10oC, Arctic grayling migrate from lakes and larger rivers to small tributary streams to spawn (Scott and Crossman 1998). Small gravel or rocky bottomed tributaries are usually preferred for spawning. When there is no suitable small streams, spawning takes place in large rivers (Scott and Crossman 1998).

2.10.5.2 Cisco Spawning Habitat

Cisco spawn in depths is 2.0 m of 64.0 m (Scott and Crossman 1998). Gravel and cobble substrates are often preferred but other rocky substrates (e.g., boulder) can provide adequate spawning habitat for this species. Usually, a hard or stony bottom is selected (Scott and Crossman 1998). The area would have clean, rocky substrates that contained sufficient crevices to allow the eggs to be protected from predators (Scott and Crossman 1998). The area must also have water circulation to provide adequate oxygen supply to the developing embryos (Scott and Crossman 1998). The slope of the shoreline or shoal should be moderate (Scott and Crossman 1998).

A good spawning area for cisco would be characterized by:

o minimum depth - 2 m; o maximum depth - 60 m; o maximum depth of rocky substrates >2 m; o gradient of rocky substrates - 10-25o; o substrate type - rocky (gravel, cobble, boulder); o substrate configuration rounded or angular; o substrate cleanliness (degree of silt or algae cover) - clean; o size of interstitial spaces >5 cm; o area of habitat >10 m2; and, o location in relation to predominant winds - open to wave action.

2.10.5.3 Lake Trout Spawning Habitat

Substrates used for spawning are usually large boulders with large, interstitial spaces mixed with some gravel (Marcus et al. 1984). The spaces between the rocks must be small enough to prevent predators from reaching the eggs (Machniak 1975) but large enough to allow adequate water circulation to maintain oxygen levels through the winter incubation period (Marcus et al. 1984). Lake trout have been observed to prefer angular rocks over smooth rocks (Marcus et al. 1984), presumably because of the greater depth and size of the interstitial spaces. Spawning has been observed to occur in water as deep as 55 m but the average depth varies from 2 m to 6 m (Martin 1955, in Machniak 1975). Eggs must be placed in water deep enough to avoid freezing during the winter. Lake trout prefer to spawn at the base of a sharp rise or drop in the lake’s contour.

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A good spawning habitat for lake trout would be characterized by:

o minimum depth - 2 m; o maximum depth -10 m; o maximum depth of rocky substrates >2 m; o gradient of rocky substrates - 30-50o; o substrate type - boulder/cobble; o substrate configuration angular; o substrate cleanliness (degree of silt or algae cover) - clean; o size and interstitial spaces >10 cm; o area of habitat >10 m2; and, o location in relation to predominant winds - open to wave action.

2.10.5.4 Round Whitefish Spawning Habitat

Round whitefish prefer to spawn in hard or stony bottom at depths of 4.0 m to 16.0 m (Scott and Crossman 1998). Substrates selected for spawning range from cobble to gravel depending on what is available to the fish. The gravel/cobble substrates must contain sufficient crevices to allow the eggs to be protected from predators. The area must also have water circulation to provide adequate oxygen supply to the developing embryos. The slope of the shoreline or shoal should be moderate.

A good spawning area for round whitefish would be characterized by:

o minimum depth - 2 m; o maximum depth - 20 m; o maximum depth of rocky substrates >2 m; o gradient of rocky substrates - 10-25o; o substrate type - gravel/cobble; o substrate configuration rounded; o substrate cleanliness (degree of silt or algae cover) - clean; o size and interstitial spaces >5 cm; o area of habitat >10 m2; and, o location in relation to predominant winds - open to wave action.

2.10.5.5 Slimy Sculpin Spawning Habitat

Slimy sculpin is a bottom dweller and typically lives and spawns between or under rocky substrates. Slimy sculpin spawn under a submerged object, such as a rock (Scott and Crossman 1998).

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2.10.6 Feeding Relationships of Major Fish Species and Stomach Content Analysis

This section presents information on the feeding relationships of the four major fish species identified for this monitoring program, i.e., Arctic grayling, cisco, lake trout and round whitefish. Information for this section was drawn from DDMI (1998a).

Arctic grayling, cisco, lake trout and round whitefish were collected in Lac de Gras and studied for stomach content during the summer and fall of 1995 (Acres and Bryant 1996b).

Cisco are commonly plankton feeders (primary consumer), occasionally feeding on some aquatic and terrestrial insects (McCart and Den Beste 1979). They play an important role in the food chain as they are at the bottom of the food chain and are preyed on by larger piscivorous fish (McCart and Den Beste 1979). Round whitefish and Arctic grayling are higher in the food chain than cisco as they pray on herbivores (secondary consumer). Round whitefish consume a variety of benthic invertebrates and are suspected to eat eggs of other fish species. Juvenile Arctic grayling feed primarily on zooplankton, whereas adults consume a broad assortment of invertebrates, including terrestrial insects obtained at the surface of the water (Scott and Crossman 1998). Lake trout generally consume a wide range of aquatic dipterans, crustaceans and small fish as juvenile. As adult, lake trout are top predator and prey on other fish species or on juvenile lake trout (McCart and Den Beste 1979; Scott and Crossman 1998). Figure 2.10-11 presents a simplified diagram of an Arctic freshwater community illustrating primary predator-prey relationships.

2.10.6.1 Stomach Content in 1995

Lake trout, round whitefish, cisco and Arctic grayling were collected in Lac de Gras and studied for stomach content during the summer and fall of 1995 (Acres and Bryant 1996b). During summer 1995, lake trout ate both insects and fish (Acres and Bryant 1996b). Large lake trout frequently preyed on fish, which formed most of their diet (Photo D7-4). Important prey species for lake trout included round whitefish, burbot, cisco and other lake trout (cannibalism). Lake trout, in fact, accounted for nearly 24% (by weight) of the food items ingested by lake trout. Caddisfly larvae and dipteran adults were the most common insect items in the diet of lake trout. About 11% of the lake trout stomachs were empty in the 1995 surveys (Acres and Bryant 1996b).

Lake trout food habits in the fall of 1995, included more zooplankton and dipterans than in summer (Acres and Bryant 1996b). However, fish remained an important food item for larger lake trout, with cisco (23% by weight) and whitefish (19% by weight) comprising the most important prey species (Acres and Bryant 1996b). Lake trout cannibalism occurred at a similar rate in summer and fall (3% by occurrence), but to a lesser degree (3% by weight) in fall. Fewer lake trout had empty stomachs (3.3%) in the fall than in the summer (11%) (Acres and Bryant 1996b).

182 SIMPLIFIED DIAGRAM OF AN ARCTIC FRESHWATER COMMUNITY ILLUSTRATING PRIMARY PREDATOR-PREY RELATIONSHIPS

FIGURE: 2.10-11 Diavik Diamond Mines Inc. AEMP Design Document 2007

In the summer of 1995, round whitefish diets were dominated by insects (approximately 90% by weight and occurrence), with only light use of zooplankton (Acres and Bryant 1996b). Caddisfly larvae were the most common food item by weight (45%), and second in percent occurrence (33%). Dipteran larvae were the most commonly occurring organism (37%). All the round whitefish examined in summer had something in their stomachs (Acres and Bryant 1996b).

The diet of round whitefish varied more in the fall of 1995 (Acres and Bryant 1996b). However, caddisfly larvae remained the most important food item by weight (34%) and by percent occurrence (64%). Round whitefish ingested snails and mussels in the fall, but not in the summer (Acres and Bryant 1996b).

In summer 1995, diet for cisco included zooplankton and insects. The single most important food item, by both percent weight and occurrence, was copepods, occurring in 55% of the stomachs and comprising about 46% by weight (Acres and Bryant 1996b). The next most commonly occurring insect food item was dipteran adults (mixture of several species). Of the dipterans, chironomid adults specifically accounted for a high percentage by weight (12%). About 8% of cisco stomachs were empty in the summer (Acres and Bryant 1996b). Cisco food habits changed substantially between summer and fall. By fall 1995, cisco were feeding almost exclusively on copepods (97% by weight and 90% by occurrence), with minor use of dipteran adults. About 8% of the cisco stomachs were also empty in fall (Acres and Bryant 1996b).

2.10.6.2 Stomach Content in 1996

In 1996, the stomach contents study focused on spring Arctic grayling, with other species represented in small numbers (Golder 1997i). At the time of capture, all grayling were either in spawning or post-spawning condition. This may affect food preference due to the high amount of energy required for spawning. Therefore, the gut contents analysis results presented here may not be representative of typical food preferences for Arctic grayling during non-spawning periods.

In spring 1996, Arctic grayling in Lac de Gras were identified as consuming primarily chironomid larvae, but were also noted as consuming other dipterans, trichoptera, coleoptera, fish eggs, terrestrial insects and plecoptera (Golder 1997i). Stomach contents from fish collected during the spring fish sampling program give a rough indication of the types and amounts of food being selected by fish during the time of sampling (Table 2.10-7).

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Table 2.10-7 Stomach contents from Arctic Grayling collected during spring 1996 in Lac de Gras

Other Undidentified Fish Aquatic Terrestrial Non- Organic Inorganic Total Eggs Insects Insects Mollusks insects Material Material volume 0.5 6.8 - - - 5.7 - 13.0 - 0.2 - - - 0.7 p 0.9 - 0.6 p - p 0.3 - 0.9 P 3.5 p p - 2.5 - 6.0 1.6 1 p - - 2 p 3.6 0.2 7.7 - - - 2.4 - 10.3 0.5 3 - - p 1.8 p 5.3 P 6.4 - - - 1.2 - 7.6 0.1 1.4 - - - 1.5 p 3.0 P 16.3 p - p 1.8 - 18.1 2.6 13 - - p 0.2 3.8 19.6 P 1.2 - - - 5.2 0.2 6.4 2.1 2.2 0.1 - 0.1 2 - 6.5 - 1.6 - - p 0.7 0.2 2.5 Source: Golder 1997i. Notes: p = negligible amount , - = not present.

2.10.6.3 Stomach Content in 2004

Little information was available on the stomach content of slimy sculpin collected from the 2004 assessment. The stomachs of the sculpin collected at REF1 were noticeably full of caddisflies, a benthic invertebrate (Gray et al. 2005). Stomach of sculpin collected in the dike A154 area also contained caddisflies although at a lesser level. No other information was available on stomach content.

In summer 1995, the two Arctic grayling that were caught had eaten a wide range of aquatic and terrestrial insects, and miscellaneous plant material (Acres and Bryant 1996b). In fall, the one grayling stomach analyzed contained 100% chironomid larvae. In spring 1996, Arctic grayling in both Lac de Gras and Lac du Sauvage were again identified as consuming primarily chironomid larvae, but also consumed other dipterans, trichopterans, coleopterans, fish eggs, terrestrial insects and plecopterans (Golder 1997i).

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2.10.7 Fishery Use in Lac de Gras

No local subsistence fishing is done by Aboriginal people in Lac de Gras, although it is a traditional fishing ground of the Yellowknives Dene (DDMI 1998b). The intensity of contemporary use by the local Dene, Metis and Inuit communities is believed to be very low (DDMI 1998b). Subsistence fishing would not likely be carried out by angling, but would involve activities such as gill netting or fish trapping.

The only other potential source of harvest pressure on the lake trout of Lac de Gras would come from recreational fishermen. The Ekati Diamond Mine has set a policy of no angling on their lease. Recreational angling has been observed in the narrows, a short stretch of the Coppermine River between Lac du Sauvage and Lac de Gras (DDMI 1998b). There are three fishing leases on Lac de Gras, all of which are owned by Qaivvik Ltd., Yellowknife. The leases have been inactive for the past few years and no activity is planned in the foreseeable future (DDMI 1998b). The only established exploration or expediting camp that operates in the regional study area is the Echo Bay Road Camp, located on the south shore of Lac de Gras (Axys and UMA Group 1998). This camp has a 50 person capacity and generally operates only during the winter, although it has occasionally been leased for exploration activities (DDMI 1998b).

2.10.8 Contaminants in Fish Tissue

This section presents contaminants information for the five major fish species and sentinel species identified for this monitoring program, i.e., Arctic grayling, cisco, lake trout, round whitefish and slimy sculpin. Information for this section was drawn from the Integrated Environmental and Socio-Economic Baseline Report (DDMI 1998a) and from the assessment of slimy sculpin collected near east island, Lac de Gras, NWT (Gray et al. 2005). Figures 2.10-12 to 2.10-16 presents the mean concentrations for metals for which consumption guidelines were available (arsenic, cadmium, copper, lead and mercury). Concentration of metals were measured in flesh, kidney and liver of artic grayling, cisco, lake trout and round whitefish sampled at locations all throughout Lac de Gras in 1996 (Golder 1997i). Summary results per species and sex for all the metals analysed from the 1996 fish survey are in Appendix II.5. Mean metal concentrations for slimy sculpin are illustrated in Figure 2.10-17 (Gray et al. 2005). Information on metals in fish tissue during construction and operations is provided in Section 3.2, as per the final Terms of Reference (WLWB and Gartner Lee 2007). No information on moisture and lipid content and concentration of metals in invertebrate were available.

Consumption guidelines for trace elements, as set out by the National Health and Medical Research Council (Reilly 1991), are as follows for edible fish tissue: o Arsenic = 1.0 µg/g; o Cadmium = 0.2 µg/g; o Copper = 10 µg/g; o Lead = 2.5 µg/g; and, o Mercury = 0.5µg/g.

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Figure 2.10-12 Arsenic Concentration in Fish Tissues Sampled in 2006

Flesh 0.3 Kidney Liver

0.25 g/g) μ 0.2

0.15

0.1 Mean Arsenic Concentration (

0.05

0 Arctic grayling cisco Lake trout Round Arctic grayling cisco Lake trout Round whitefish whitefish male female

------Detection limit Calculation at Half the Detection Limit

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Figure 2.10-13 Cadmium Concentration in Fish Tissues Sampled in 2006

Flesh

1.6 Kidney Liver

1.4

1.2 g/g) μ

0.8

0.6

0.4 Mean Cadmium Concentration ( Mean

0.2

0 Arctic grayling cisco Lake trout Round Arctic grayling cisco Lake trout Round whitefish whitefish male female

------Detection limit ………… Consumption Guideline

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Figure 2.10-14 Copper Concentration in Fish Tissues Sampled in 2006

Flesh

20 Kidney Liver g/g) μ

10 Mean Copper Concentration ( 5

0 Arctic grayling cisco Lake trout Round Arctic grayling cisco Lake trout Round whitefish whitefish male female ------Detection limit ……….. Consumption Guideline

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Figure 2.10-15 Lead Concentration in Fish Tissues Sampled in 2006

0.2

0.18 Flesh Kidney 0.16 Liver

0.14 g/g) μ

0.12

0.1

0.08

0.06 Mean LeadMean Concentration (

0.04

0.02

0 Arctic grayling cisco Lake trout Round Arctic grayling cisco Lake trout Round whitefish whitefish male female ------Detection limit Calculation at Half the Detection Limit

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Figure 2.10-16 Mercury Concentration in Fish Tissues Sampled in 2006

0.6

0.5 Flesh Kidney g/g) μ 0.4 Liver

0.3

0.2 Mean Mercury Concentration ( Mercury Mean

0.1

0 Arctic grayling cisco Lake trout Round Arctic grayling cisco Lake trout Round whitefish whitefish male female ------Detection Limit ………. Consumption Guideline

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Figure 2.10-17 Metal Concentrations in Slimy Sculpin and Mean Concentrations of Metals in Lake Trout Flesh

Slimy Sculpin Reference

Slimy Sculpin A154 Dike

Lake Trout

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2.10.8.1 Species Sampled in 1996

Arsenic

Average concentrations of arsenic in all tissues and all species were below consumption guideline of 1 μg/g. Average concentration of arsenic in Arctic grayling were higher in the kidney than in the other tissues for both males and females (Figure 2.10-12). Males and females had levels of arsenic in kidney of 0.19 μg/g compared to levels below detection limits in other tissues.

Female lake trout also had higher levels of arsenic in kidney than in other tissues. Mean concentration in kidney was 0.25 μg/g compered to levels below detection levels in other female tissues and all males tissues. Cisco and round whitefish had levels of arsenic below detection limits for all tissues (Figure 2.10-12).

Cadmium

For the four species sampled in 1996, levels of cadmium in flesh and liver were below consumption guideline of 0.2 μg/g (Figure 2.10-13). Concentrations in flesh were actually below detection limit of 0.02 μg/g for all species. Mean concentrations in liver varied from 0.09 μg/g to 0.21 μg/g. Levels of cadmium in kidneys were all above consumption guideline for all the species, (Figure 2.10-13). Mean concentrations of cadmium in kidney varied from 0.25 μg/g to 0.58 μg/g except for female lake trout, which had a mean concentration of 1.52 μg/g (Figure 2.10-13).

Copper

Levels of copper in tissues were usually noticeably lower than the consumption guideline of 10 μg/g with the exception of lake trout levels in liver (Figure 2.10-14). Mean concentrations in flesh varied from 0.34 μg/g to 1.32 μg/g, whereas levels in kidney ranged from 0.54 μg/g to 2.10 μg/g. Males and females lake trout had mean concentrations of copper in liver of 19.34 μg/g and 10.53 μg/g respectively.

Lead

Average concentrations of lead in all tissues and all species were below consumption guideline of 2.5 μg/g (Figure 2.10-15). The highest mean concentrations were measured in round whitefish kidney, with 0.18 μg/g for males and 0.19 μg/g for females. Levels of lead in liver ranged from below detection limit to 0.12 μg/g. Mean concentrations in flesh were usually below detection limit except oft female round whitefish, where the mean concentration was 0.02 μg/g (Figure 2.10-15).

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Mercury

Mean concentrations for mercury were below the consumption guideline of 0.5 μg/g, except for one (Figure 2.10-16). Mean concentration for male lake trout kidney was equal to the guideline. From the five fish sampled, only one fish had a mercury concentration in the kidney above the guideline (Lake trout fish #18 =1 μg/g). The other specimen had concentrations between 0.26 μg/g and 0.49 μg/g (Golder 1997i).

The concentrations of mercury measured in liver were higher in lake trout than in other species with concentrations of 0.39 μg/g in males and 0.25 μg/g in females. Other species had concentrations in liver ranging from 0.06 μg/g to 0.14 μg/g. From all tissues, flesh had the lowest levels of mercury; mean concentrations varied from 0.03 μg/g to 0.26 μg/g (Figure 2.10-16).

2.10.8.2 Slimy Sculpin 2005

Slimy sculpin were collected at two sites (reference and close to dike A-154). At each site, 20 slimy sculpin were sampled, head and all visceral organs (gut, liver, gonads, bladder) were removed, and the kidneys dissected. Metals analyses were conducted on homogenized body carcass tissues (i.e., predominantly muscle tissue).

Results from the metal analyses are presented in association with the mean metal concentrations in lake trout flesh (Figure 2.10-17). Most metal concentrations in sculpin correspond similarly to levels in lake trout in 1996. Exceptions are iron, manganese, and zinc, which are higher in sculpin carcass tissue than those found in other fish species (McCarthy et al. 1997).

2.10.8.3 Consumption Guidelines

For flesh samples, none of the four large bodied-species (lake trout, round whitefish, cisco, and Arctic grayling) tested had mercury, arsenic, copper, cadmium or lead concentrations in their flesh tissues that were above the consumption guidelines. In Arctic grayling, cadmium levels were twice the levels recommended by consumption guideline. For all other species, cadmium levels were almost always above the consumption guidelines, especially in lake trout.

Liver samples were taken from lake trout and results indicated that the samples were at or above the consumption guidelines. Livers from females were slightly above the guidelines whereas males were 2.0 to 2.5 times over.

Concentrations of metals in slimy sculpin flesh tissue samples were very low. No slimy sculpin tested for metals had a concentration equal to or above consumption guidelines (Gray et al. 2005).

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2.11 INTEGRATION

The goal of this section is to summarize information presented in Sections 1 and 2, and include additional information as necessary from the 1998 EA (DDMI 1998a, 1998b and 1998d) to describe the aquatic environment of Lac de Gras. Information is provided below for the following requirements of the final Terms of Reference (WLWB and Gartner Lee 2007):

o summary of Lac de Gras in a regional context; o ecological characteristics and relationships within Lac de Gras and description of the lake’s ecology; o physical, chemical, and biological characteristics of the lake interactions; o adequacy of the baseline data to inform the AEMP; o data or information gaps; o key elements of the lake’s expected sensitivities; o map of key features of baseline conditions, mine components, any sampling locations referenced, and SNP sites; o an overview of the lake over the past 200 years of human habitation as informed by traditional knowledge (TK); o discussion relating expected response of baseline conditions to climate change; and, o graphic illustrating the food web of Lac de Gras, including linkages to wildlife.

The second, third, and last bullet all refer to interactions, relationships, and linkages within Lac de Gras. They have been combined to form a more comprehensive discussion of the lake’s ecology. Therefore, the content of these three topics is included in Section 2.11.2.

2.11.1 Lac de Gras in a Regional Context

A summary of Lac de Gras in a regional context was requested in the final Terms of Reference (WLWB and Gartner Lee 2007). Various data sources were compared with Lac de Gras baseline data (BHPB 1995; Moore 1978a, 1978b; Peramaki and Stone 2005; Pienitz et al. 1997a, 1997b; Ruhland et al. 2003; Shortreed and Stockner 1986). Water chemistry, limnology, chlorophyll a concentrations, and sediment chemistry were the selected elements used in the comparison. Locations of the lakes used in the comparison are presented in Figure 2.11-1.

2.11.1.1 Water Chemistry and Limnology

Section 2.5.3 presents a detailed comparison of Lake de Gras water chemistry to other lakes in the area and in the Arctic region. Baseline data from Lac de Gras were compared to water chemistry collected from 1975 to 1996 in the NWT and Yukon. This section will present a brief summary of the main findings.

195 Area 1

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Y GIS JSB 15/02/07 \ S I CHECK G \ FIGURE: 2.11-1 : REVIEW G Diavik Diamond Mines Inc. AEMP Design Document 2007

The majority of the lakes studied stratified during the open water season in contrast to Lac de Gras. Lac de Gras is a large and particularly long lake (surface area of 572 km2, length of 60.5 km). Consequently, it is strongly exposed to wind, which favours good vertical mixing and prevents thermal stratification (DDMI 1998a). Studied lakes were usually smaller (surface area varying from 0.009 km2 to 90 km2) (Pienitz et al. 1997a, 1997b; Ruhland et al. 2003; and, Shorttreed and Stockner 1986). Contowyto Lake (surface area of 950 km2) and Lac du Sauvage (surface area of 120 km2) were the largest lakes included in the regional comparisons. Twenty eight of the 33 lakes studied by Ruhland et al. (2003) in NWT and Nunavut were stratified, six of them strongly. Studies conducted by Pienitz et al. (1997a, 1997b) also show that the majority of the lakes studied stratified. Stratification can limit recycling of nutrients during the open water season (Straskraba 1978; Riley and Prepas 1985 all in Golder 1999).

The water quality of Lac de Gras is very similar to other northern lakes in central NWT with very low levels/concentrations of conductivity and ions. Lakes sampled in the Yukon and extreme north-west portion of NWT (referred to here as Yukon lakes) usually had higher concentrations of ions, which was partially explained by the differences in geologic formations and proximity to the ocean. Conductivity in lakes in the central NWT ranged from 5.8 μS/cm to 20 μS/cm. The mean conductivity of water from Lac de Gras was 7.9 μS/cm to 12.3 µS/cm. In contrast, the lakes in the Yukon had a mean conductivity of 128.5 μS/cm. The conductivity was higher in the Yukon lakes because of higher concentrations of major ions. Within the central NWT, all lakes including Lac de Gras had similar concentrations of calcium, chloride, potassium, and sodium, with levels ranging form 0.27 mg/L to 1 mg/L (Tables 2.5-5 to 2.5-8). The concentration of calcium in the Yukon lakes was 9.6 mg/L (Table 2.5-8).

Metal concentrations were usually below detection limits in Lac de Gras and in nearby lakes. Lakes in the Yellowknife area sampled in 1998 had higher concentrations of all metals analyzed (aluminum, barium, lead, lithium, and manganese) except strontium. Yukon lakes also had higher concentrations of metals analyzed (iron and manganese) (Table 2.5-7).

Nutrient concentrations presented a similar pattern, with Lac de Gras and the central NWT lakes displaying low nutrient concentrations and the Yukon lakes displaying the highest concentrations of TKN and total phosphorus. The lowest TKN was in Lac de Gras with concentrations of 0.08 mg/L compared to 0.123 mg/L and 0.307 mg/L in central NWT lakes and Yukon Lakes respectively (Table 2.5-8). Lac de Gras was part of the lakes that had the lowest concentrations of total phosphorus, with concentrations below detection limits.

Concentrations of chlorophyll a measured during the open water season were low and very similar among the studied lakes (Table 2.11-1). Concentrations during the open water season were usually close to or below 1 mg/L. Concentrations of chlorophyll a measured during the ice-covered season were also similar between Lac de Gras and the lakes sampled in the Yukon area (Table 2.11-1).

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Table 2.11-1 Range of Chlorophyll a Concentrations During Open Water and Ice-covered Seasons

Chlorophyll a (µg/L) Lake Open Water Ice-covered Reference Season Season (a) Lac de Gras (baseline) 0.32 - 4 0.25 – 1.46 Golder 1998; DDMI 2001 Lac du Sauvage 0.5 – 1.5 - Golder 1998 13 Arctic tundra lakes, Great Slave Lake area (NWT) 0.5 – 1.8 - Pienitz et al. 1997a 18 Arctic tundra lakes, Great Slave Lake area (NWT) 0.4 - 6.7 - Ruhland et al. 2003 24 Arctic tundra lakes, Yukon and NWT 0.1 – 1.3 - Pienitz et al. 1997b 19 sub-Arctic lakes,Yukon 0.62 - 3.76 0.56 - 3.32 Shortreed and Stockner 1986 a = In general, chlorophyll concentrations were below or close to 1 µg/L. Levels of 3 µg/L to 4 µg/L were only measured once (for both samples).

Overall, Lac de Gras is comparable to other lakes in central NWT. Its conductivity, nutrients, and chlorophyll a are lower than, or similar to, other lakes in central NWT.

2.11.1.2 Sediment Chemistry

Sediment samples were collected in four lakes in the Coppermine River basin (Lac de Gras, Desteffany Lake, Point Lake, and Daring Lake) in 2000 and analyzed for arsenic, copper, lead, and mercury (Peramaki and Stone 2005). Samples were fractioned every centimetre and dated using 210Pb. The results are presented in Table 2.11-2 and Figures 2.11-2 to 2.11-5.

Arsenic concentrations in Lac de Gras sediment with a mean concentration of 264.9 mg/kg were higher than in the other lakes (Table 2.11-2). Other lakes had arsenic mean concentrations ranging from 6 mg/kg to 20.1 mg/kg. Arsenic concentration in Lac de Gras was particularly high in the 4 cm to 7 cm fractions, corresponding to the 1944 to 1980 period (Figure 2.11-2).

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Table 2.11-2 Metal Concentrations (mg/kg) in Sediment Cores Sampled in 2000

Lac de Gras Desteffany Lake Point Lake Daring Lake N = 15 N = 19 N = 15 N = 20 Arsenic Mean 264.9 10.2 20.1 6 Range 43.4-753.0 5.2-59.9 16.8-24.2 4.0-20.3 Copper Mean 105.3 49.2 69.2 23.3 Range 84.4-129.0 44.5-62.5 54.5-92.6 19.6-26.8 Lead Mean 6.5 6.9 9.5 5.1 Range 4.0-9.8 6.0-12.8 7.5-15.3 4.2-10.7 Mercury Mean 0.06 0.06 0.05 0.02 Range 0.05-0.09 0.04-0.12 0.04-0.08 <0.01-0.04 Source: Peramaki and Stone 2005. Note: N = sample size.

Copper was also elevated in Lac de Gras sediments compared to sediments in other lakes. The mean concentration of copper in Lac de Gras sediment was 105.3 mg/kg, while mean concentrations for other lakes varied from 23.3 mg/kg to 69.2 mg/kg. In Lac de Gras, copper concentrations in sediments were more variable among the fractions than in other lakes and tended to increase with depth (Figure 2.11-3).

Lead and mercury were similar among the lakes. Concentrations of lead varied from 5.1 mg/kg to 9.5 mg/kg, whereas mercury mean concentrations varied from 0.02 mg/kg to 0.06 mg/kg (Table 2.11-2). Lead concentrations in Desteffany Lake, Point Lake, and Daring Lake were higher in the 0-1 cm fraction than in lower fractions (Figure 2.11-4). Lead concentrations in Lac de Gras were generally higher in the 0 – 1 cm fraction although the concentrations varied between fractions and years (Figure 2.11-4). Similarly, concentrations of mercury in the upper fractions of the soil cores tended to be greater than concentrations in lower fractions (Figure 2.11-5).

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Figure 2.11-2 Arsenic Concentrations (mg/kg) in Sediment Cores Sampled in 2000

Figure 2.11-3 Copper Concentrations (mg/kg) in Sediment Cores Sampled in 2000

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Figure 2.11-4 Lead Concentrations (mg/kg) in Sediment Cores Sampled in 2000

Figure 2.11-5 Mercury Concentrations (mg/kg) in Sediment Cores Sampled in 2000

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2.11.2 Ecological Characteristics of Lac de Gras

The Lac de Gras watershed is located close to the southern boundary of the Low Arctic region, north of the tree line boundary, in the central barren-ground tundra of the NWT. The climate of the Low Arctic is characterized by long, cold winters and short, cool summers. January is typically the coldest month of the year in the region of Lac de Gras, with a mean daily air temperature of approximately -30°C. July is typically the warmest month, with mean daily temperatures of approximately 10oC, which is enhanced by long periods of daylight. The mean annual precipitation is less than 400 mm (ESWG 1995). Wind measurements at the Diavik site at Lac de Gras tend to show a prevailing wind from the northwest with an average wind speed of about 20 km/hr. On an annual basis, calms (winds less than 1 m /s) are expected to occur about 3% of the time.

The presence of permafrost strongly affects hydrology in the Arctic. The freezing and thawing of the active layer controls surface water runoff, which affects water levels and flows. Surface runoff is highest when the active layer is frozen because water cannot infiltrate the soil. Very high surface runoff yields are common in the Arctic during snowmelt when the active layer is frozen (DDMI 1998a).

Arctic geology influences the water quality of lakes such as Lac de Gras. The amount of dissolved substances in surface runoff depends on the nature of the parent rock. Surface run-off from Canadian Shield bedrock contains few particulate or dissolved components compared to run-off from sedimentary bedrock (EC 1988 in BHPB 1995). The low input of dissolved substances into Lac de Gras creates low productivity of fish and other aquatic organisms. Lac de Gras is classified as an ultra-oligotrophic lake based, in part, on its concentration of phosphorus and nitrogen, both elements essential to the growth of vegetation (Wetzel 2004). Because Lac de Gras has a low nutrient input, concentrations of all nutrients are usually low in the water column. Also, lakes in the region are known to be sensitive to acidification because of their low buffering capacity (Pienitz et al. 1997a).

The food web of Lac de Gras is influenced by it’s physical environment: geology (Canadian Shield bedrock), extreme climate, exposure to high winds due to its length (60.6 km), rough shoreline, and location beyond the treeline. Foodwebs of freshwater aquatic communities in the Arctic generally include various species of aquatic plants (phytoplankton, periphyton, and macrophytes), zooplankton, benthic invertebrates, and fish (Figure 2.11-6). Fish tend to be an important link between the aquatic and the terrestrial food webs as they are consumed by birds (e.g. loons and terns), wildlife (e.g., bears), and human beings.

There are almost no large rooted aquatic plants along the rugged shorelines of the open water areas of Lac de Gras likely due to the unsuitable substrate (mainly boulders), abrasive action of wind-driven waves and ice scour, and limited nutrients. The relative lack of large aquatic plants in the littoral zone as well as the lack of overhanging vegetation (e.g., trees) in the barren ground tundra means that little organic material is added to the lake further limiting productivity in the littoral zone. Rooted aquatic plants were found in sheltered areas and willows were observed at inlet streams. Although important habitat for some fish species, the contribution of these small isolated communities would be minimal to the overall lake productivity.

202 Terrestrial Animals

Plankton

Aquatic Feeding Birds

Small Bodied Fish

Aquatic Invertebrate

Large Bodied Fish

GENERAL FOOD WEB OF AN ARCTIC LAKE Ingestion

FIGURE: 2.11-6 Diavik Diamond Mines Inc. AEMP Design Document 2007

No data are available for algae growing on the substrate (periphyton) although periphyton would likely be limited in that part of the littoral zone affected by ice scour and wave action. Below this upper zone, periphyton is likely present, forming the basis for the benthic invertebrate community. Based on available information, phytoplankton form the basis of the pelagic or open water aquatic food chain in Lac de Gras. The high transparency of Lac de Gras water would favour photosynthesis; however, when nutrient concentrations are low, as is found in Lac de Gras, the amount of periphyton and phytoplankton growth is limited.

These primary producers are consumed by various species of zooplankton, benthic invertebrates, and fish. The stomach contents of fish captured at Lac de Gras demonstrate the importance of two major components of the foodweb:

o a sediment based component; and, o an open water component.

The benthic invertebrate community of Lac de Gras (see Section 2.9.4.1 for details) was characterized by low, but highly variable, benthic invertebrate density. This density likely reflects a low, but highly variable, supply of food (e.g., periphyton, detritus, other invertebrates), although no data are available. Invertebrate abundance and richness generally declined with increasing water depth with a sharp decline between 15 m and 20 m (see also Section 2.9.5). The area below this sharp decline represents about 10% to 20% of the total lake area. The midge family (Chironomidae), which was numerically dominant in the benthic invertebrate community was negatively correlated with depth. Benthic invertebrates are an important source of food for three of the key fish species in Lac de Gras: juvenile and adult Arctic grayling, juvenile lake trout, and juvenile and adult round whitefish. Juvenile lake trout generally consume a wide range of aquatic dipterans, crustaceans and small fish. Round whitefish consume a variety of benthic invertebrates that live attached to the rocks. Shorelines with rocky substrates that provide cover for invertebrates, are preferred foraging habitat. The sediment based component of the food web, therefore, would likely contribute most to overall productivity in the shallower areas of the lake.

Lake whitefish are primarily bottom dwellers, feeding on snails, clams, chironomids, and small fish. However, they are an exception in that they use both the shallow and deep bottom habitats. Although young lake whitefish are commonly found at the surface in shallow water areas, juveniles move to deeper water (3 m to 15 m) as water temperatures warm. Lake whitefish are frequently found at depths greater than 10 m for most of the year. Invertebrate density is limited at these depths in Lac de Gras.

The open water (pelagic) component of the food web is supported by the phytoplankton. Based on data from 1997, the phytoplankton community in Lac de Gras is typical of nutrient-poor northern lakes. The mid-summer phytoplankton community was dominated by the chrysophyceae including the genera Chromulina (very small, motile, single celled algae) and Dinobryon (larger colonial algae) (Table 2.7-7). The chrysophyceae are generally a preferred food supply for zooplankton because their size makes them easy to

204 Diavik Diamond Mines Inc. AEMP Design Document 2007 ingest. Small phytoplankton (e.g., chrysophyceae) can be very productive because of their small surface area to volume ratio, which enhances nutrient uptake. Chromulina accounted for approximately 60% of the total density of phytoplankton based on number of organisms. Because of their small size they would account for a lower percentage of biomass. Dinobryon is a wide spread genus; however, some species are limited to water bodies with low phosphorus concentrations (Wetzel 2004). The remaining plankton included green, blue-green, and other algae.

Zooplankton can be primary consumers (i.e., herbivores), secondary consumers preying on other zooplankton or both since they tend to select by size rather than trophic level. Depending on the species, zooplankton may feed on phytoplankton, bacteria, detritus, and/or smaller zooplankton. Zooplankton biomass collected during the open water season was very low (Golder 1998). Rotifers were the dominant group (based on number of individuals), followed by copepods. However, copepods are generally larger than rotifers. Based on the stomach contents of fish, copepods were more important to the food web. Fish generally tend to select by size preferring larger zooplankton.

Cisco are an open water species, usually forming large schools at mid-depth. Cisco are commonly zooplankton feeders and therefore important consumers in the open water area of the lake. In the summer of 1995, the single most important food item, both by percent weight and occurrence, was copepods (Acres and Bryant 1996b), although Cisco occasionally feed on some aquatic and terrestrial insects. During the summer of 1995, chironomid adults formed the next most common items in their diet (after zooplankton), but in the fall their consumption changed substantially and cisco were feeding almost exclusively on copepods. Since copepods store lipids, they are a valuable food resource providing additional energy for overwintering. Cisco play an important role in the open water component of the Lac de Gras food web as they are preyed on by larger piscivorous fish.

Adult lake trout commonly prey on fish including cisco, whitefish, sculpin, longnose sucker, and juvenile lake trout. Lake trout are the dominant species in area lakes and are an important food fish for humans in the region. An important link between the aquatic and terrestrial ecosystems of the arctic is the consumption of fish by several bird (e.g., loons and terns) and wildlife species (e.g., grizzly bears) (DDMI 1998a).

Based on catch records from 1996, cisco and lake trout were abundant in Lac de Gras. Density of round whitefish appeared to be lower than that for lake trout or cisco. Arctic grayling may have been present in higher numbers than the catch records indicated because they tend to reside near the mouths of tributaries, which were not sampled during the baseline field studies (Golder 1997i). Arctic grayling take advantage of the high surface runoff yields in the Arctic and spawn in small tributary streams during peak spring flows. Juveniles frequent streams until flows are too low for them to use this habitat. Juvenile Arctic grayling feed primarily on zooplankton; although they tend to remain close to the mouth of streams. The remainder of the nine species identified in Lac de Gras were not as common and likely not as important from the perspective of lake productivity.

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Lac de Gras supports a stable, slow-growing community of coldwater fish, characteristic of a cold, ultra-oligotrophic lake and similar to other un-exploited Arctic lakes (Hobbie 1973). Despite the low productivity of the lake due to ultra-oligotrophic status and cold temperatures, the biomass of fish is higher than that of similar lakes (McCart and Den Beste 1979). The higher biomass is largely due to the longevity of the species present, especially lake trout. Therefore, the total biomass of all fish present in Lac de Gras represents the incremental accumulation of many years of low annual production. The low productivity and slower growth also result in lower reproductive rates: adult fish may spawn only every second or third year once they reach maturity (Scott and Crossman 1998).

2.11.3 Adequacy of the Baseline Data and Information Gaps

The final Terms of Reference (WLWB and Gartner Lee 2007) requested information on the adequacy of baseline data to inform the AEMP (Section 2.11 d) and information gaps that exist in available baseline data (Section 2.11 e). This information has been provided below for water quality, sediment quality, phytoplankton and zooplankton, and benthic invertebrates.

Water Quality

Due to the relatively high detection limits in the baseline time period and changes in the laboratory used over time, baseline water quality data collected prior to 2000 and analyzed using laboratory facilities would have limited use in the revised AEMP (see Section 2.5.1). More specifically, baseline concentrations for total metals, major ions, and nutrients in Lac de Gras prior to 2000 will not be carried forward for use in the revised AEMP. However, baseline water quality data collected in 2000 could be incorporated into a trend analysis, because of consistency in analytical laboratory and detection limits with sampling conducted in later years. Baseline limnological data collected from field programs (e.g., dissolved oxygen, temperature, turbidity, as reported in Section 2.4) could still be used in the revised AEMP, as their measurements do not involve changes in detection limits or the laboratory used.

Sediment Quality

Previous AEMP sediment data were collected using limited replication per area (e.g., n = 1 in the near-, mid-, and far-fields). While a power analysis has not been performed on the previously collected sediment data, given the heterogeneous nature of sediments, the usefulness of the historic data in making temporal comparisons is likely limited. The revised AEMP sediment chemistry data will be collected using greater sampling effort (n = 5) per area (see Section 5). A power analysis of baseline (pre AEMP) and previously collected AEMP data could be performed to determine the usefulness of the historic data for temporal comparisons; however, as discussed in Section 5.3, the sampling protocols are to be altered to better reflect more recently deposited sediments. The sediment- chemistry depth profile will change from a 5-cm to a 2-cm depth. Due to the limitations of previously collected data and the change in sediment sampling depth, sediment data analysis and interpretation will focus on reference/exposure area comparisons. One of the

206 Diavik Diamond Mines Inc. AEMP Design Document 2007 most significant factors controlling bed-sediment capacity for collecting and concentrating trace metals is grain size – as grain size decreases, metal levels increase (Horowitz and Elrick 1988). Similarly, organic matter is known to act as a scavenger of metals. As a result, bed sediments can display marked chemical heterogeneity, even over relatively short distances. Corrections for metal-scavenging parameters such as total organic carbon or particle size distribution may be required to interpret sediment site differences in the revised AEMP.

Phytoplankton and Zooplankton

Existing chlorophyll a and zooplankton density data as well as available community composition data were presented in Sections 2.7 and 2.8. The baseline plankton data included community composition and biomass of both the plankton and zooplankton communities as well as chlorophyll a concentrations.

A data gap exists in the plankton community composition data; however, proposed analysis of a sub-set of archived samples will provide additional data required for further assessment. Proposed analysis of the archived historical samples will provide additional data that can be compared to baseline conditions to assess potential changes in community composition and biomass (see Section 5 for details). Plankton community structure is inherently variable and species replacement can occur naturally within plankton communities and may not necessarily be related to the Mine. Therefore, the plankton data will be assessed as one line of evidence for monitoring for Mine-related effects.

Benthic Invertebrates

The available benthic invertebrate data from baseline surveys and the original AEMP are generally adequate for use in developing the AEMP. There are concerns over methods changes among years, which preclude use of 1994 and 1995 data. However, the 1996 and 1997 baseline data are comparable to 2001 to 2006 AEMP data in terms of methods, and allow the estimation of among-station and among-year variability, as well as the required sampling effort. Evaluation of habitat relationships was complicated by the potential confounding influence of effluent effects, but this is not a significant issue for the AEMP design because the influence of water depth in large lakes is a known factor and can be accounted for by standardizing water depth.

2.11.4 Key Elements of Lake Sensitivity

Based on the Key Questions and VEC’s identified in the 1998 EA, the potential Mine effects and, consequently, sensitive elements in Lac de Gras were associated with water quality and fish. The results of the EA analysis indicated that changes to water supply resulting from the Mine would be very small and they were not expected to be measurable (DDMI 1998b).

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Potential effects on water quality were expected from dike constructions, mine water discharges, runoff from the east island, dust, and air emissions. However, dike construction, post-closure runoff, and mine water discharge were the only activities expected to have effects rated above negligible on water quality (DDMI 1998b).

Concentrations of aluminum, cadmium, and copper are sensitive elements as they were expected to increase during dike construction and post-closure. The levels were expected to exceed ambient water quality thresholds for the protection of aquatic life in some areas of the lake during those phases (DDMI 1998b).

In addition, phosphorus concentration is considered an element of importance due to the predicted increase in some areas of Lac de Gras from the discharge of treated mine effluent during dike construction and post-closure runoff. The site-specific threshold established to protect the existing level of productivity of Lac de Gras was 0.005 mg/L for the whole lake. Up to 20% of the surface area of Lac de Gras was expected to exceed the threshold during operations (DDMI 1998b). Increased phosphorus concentrations could affect higher trophic levels (e.g., increases in algal growth, increases in fish growth rates, improvements in fish health, and changes in the abundance of some aquatic species).

Potential effects on the fish populations were expected in Lac de Gras as well as in lakes and streams of the east island. Potential effects included direct fish mortality, changes in fish habitat and changes in fish quality (DDMI 1998b).

Angling, use of explosives in mining, dike and north inlet construction and dewatering, and the water intake pump were the main expected causes of direct fish mortality predicted in the 1998 EA. According to the EA, all the activities were expected to have negligible effects on direct mortality (DDMI 1998b). There was no fish mortality due to the water intake predicted (DDMI November 2005d). A review of various studies showed that fish mortality due to dewatering was considered negligible (DDMI 2005). Fish mortality due to dewatering of the north inlet and dikes was re-assessed because the mortality of fish in the salvage was higher than expected in the environmental assessment (DDMI 2005). The criteria for assessing the magnitude of effect also changed from the environmental assessment to this review (EA Review). Fish mortality due to the dewatering of dikes was revised from a Level I Local Effect of negligible magnitude in the environmental assessment to a Level I Regional Effect of low magnitude – hence the reason it was classified negligible. Fish mortality due to explosive use was also negligible (DDMI 2005). Angling was banned by DDMI; however fish were harvested for fish palatability and texture studies by the aboriginal communities. The effect of these on overall fish mortality is low (DDMI 2005).

Fish habitat is a sensitive element as some loss from dike and infrastructure constructions were predicted in the original EA. The main effects were expected for slimy sculpin habitat and inland lakes on east island (DDMI 1998b). Slimy sculpin habitat was expected to be reduced by up to 7.7% during the construction and operations phases. An effect of high magnitude and mid-term duration was predicted for fish-bearing lakes on the east island by

208 Diavik Diamond Mines Inc. AEMP Design Document 2007 the loss of four fish-bearing lakes on the east island during construction and operations. Mitigation and compensation measures were designed during all phases (DDMI 1998b).

The potential for higher metal concentrations in fish flesh or for tainting in fish in Lac de Gras or east island lakes was considered negligible (DDMI 1998b). However, post-closure runoff to two lakes on the east island could result in elevated metals concentrations in fish flesh in those two lakes (DDMI 1998b). Fish quality in those two lakes could be a sensitive element at closure. The potential of this effect will be evaluated further based on actual runoff monitoring information collected during operations.

2.11.5 Summary Map

Section 2.11 g) of the final Terms of Reference (WLWB and Gartner Lee 2007) requested a map “showing key features of baseline conditions, mine components, any sampling locations referenced and SNP sites”. Therefore, the following section provides two maps presenting baseline features and sampling sites.

Figure 2.11-7 illustrates baseline features, including original shoreline, the Mine footprint and lake depth. Figure 2.11-7 presents the sampling sites for baseline information regarding water and sediment chemistry, phytoplankton and zooplankton, and benthic invertebrates collected in 1995 to 1997 and 2000, SNP sites, and AEMP sites. Figure 2.11-1 presents the location of the lakes used in the regional comparison.

2.11.6 Traditional Knowledge of Lac de Gras

Although the area around Lac de Gras is sparsely populated, it has been used by three groups of Aboriginal peoples: the Inuit, Métis, and Dene for centuries (DDMI 1998a). In recent years, the intensity of fishing, trapping, and hunting has been relatively light. However that does not diminish the level of concern from the Aboriginal people for the landscape and its wildlife (DDMI 1998d).

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During the early phase of the Mine conception, DDMI presented the initial mine concepts to local communities in informal discussions. A series of meetings were later held with Dene, Métis and Inuit community leaders to formally present the initial project concepts. With contributions from the local communities, DDMI wanted to get an understanding of the functioning of ecosystems, resource abundance, cycles and distribution, land and resources management, social, economic and cultural conditions and the relationship between these factors (DDMI 1998d). Many local people shared their traditional knowledge with DDMI. In addition, DDMI started an issues database at the beginning of the project (DDMI 1998d). TK issues identified by the local communities that pertain to Lac de Gras included the following:

o discuss TK, provide and update of activities at Lac de Gras; o documentation of Yellowknife Dene First Nations YKDFN knowledge about their traditional and current use of lands around Ekati (Lac de Gras); o TK should be a part of all disciplines; o Elders would like a TK study for the Lac de Gras area. They mentioned that the Caribou migration map for instance, would be a good map to tie with the scientific side; o integrate TK in EA and decision making. Ensure equal treatment of TK; and, o mitigation measures should be based on TK. TK used to determine camp location, buffer zone for Caribou. Integration of TK into Baseline Report. Will TK be incorporated into the management of water for the Mine site?

One of the concerns was whether TK would be incorporated into the management of water for the Mine site. A complete list of all the TK issues can be found in the issues database (DDMI 1998e). All the issues in the database are tagged as action items and linked to EA and EA supporting documents (DDMI 1998e).

Diavik has financially supported a number of TK studies (DDMI 1998a) including the following:

o Caribou Migration Patterns and the State of Their Habitat (Dogrib Renewable Resources Committee and Dogrib Treaty 11 Council 1997); o Community Based Monitoring in the Slave Geological Province (Parlee and Lutsel K'e First Nation 1997); o Naonaiyaotit Traditional Knowledge Report (DDMI 1998a); o The Habitat of Dogrib Traditional Territory (DDMI 1998a); and, o Yellowknives Dene First Nation Traditional Knowledge Report (DDMI 1998a).

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Reports for other TK studies conducted in the region were also reviewed and included:

o Nihat’ni: Watching the Land – Final Report 2003 – 2005 (Lutsel Ke Dene First Nations); o Traditional Knowledge in the Kache Tue Study Region: Phase Three – Towards a Comprehensive Environmental Monitoring Program in the Kakinye Region (2002 Autsyl K’e Dene First Nation); o Traditional Ecological Knowledge in the Kache Tue Study Region (2001 Lutsel K’e Dene First Nation); and, o Dogrib Knowledge on Placenames, Caribou and Habitat (2002 Dogrib Treaty 11 Council).

From the review of the TK reports, the following was noted:

o the TK provide information on historical activities in the area; o the information in the TK reports do not specifically refer to Lac de Gras. The lakes referred to include the Great Slave Lake, Great Bear Lake, Mackay Lake, Aylmer Lake, Artillery Lake, McKinlay Lake; o the Weledeh Yellowknives Dene (1997) TK report description of their territory places Lac de Gras at the center of it; o with regards to the aquatic ecosystem, there is some TK information on fish abundance and health; and, o there is some mention of the effects of the hydroelectric power station and mining on water quality.

One of the TK studies (Weledeh Yellowknives Dene 1997) did make recommendations to mining companies and they included the following:

o involve Elders and Dene land owners to participate actively in developing mechanisms in monitoring and in monitoring impacts from mining operations on water quality, water flow, water level, fish aquatic plants, and wildlife relying on water; o obtain consent from elders for land and water use; o avoid and protect archaeological sites and ecologically and environmentally sensitive areas (fish spawning areas, caribou migration routes, eskers), and to fund indigenous people’s identification of such sites; o obtain Dene approval prior to using contract archaeologists; o be responsible for habitat damage, contamination, and subsequent reclamation; o minimize effects on fish and wildlife caused by habitat disturbance; and, o compensate indigenous people for loss of use of territory while continuing to have access within their complete territory.

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DDMI has used community information gathered during the public consultation process and the different TK studies to guide the development of environmental baseline studies, the development of the Environmental Management System, mitigation measures and the development of monitoring programs (CEAA 1999). By identifying what environmental components aboriginal people value, Diavik sought to incorporate this information into the project design process, the development of the Environmental Management System, mitigation measures, and the development of monitoring programs. In particular, elders who visited the proposed mine site provided valuable information that influenced the project design. Their knowledge of caribou movements, wildlife habitat, natural drainage patterns, blowing snow and seasonal changes in ice conditions assisted Diavik in determining specific locations and design features for various project components.

The studies summarized in Section 3 of this document reflect the historical context of the lake. Other studies that have been carried out include Fish Palatability and Texture Studies (DDMI 2003b, 2006b). The monitored baseline program does reflect, but in a limited way, the historical context of the lake and it’s users because it includes the monitoring of groundwater, mine water and water runoff, process effluent, surface water, aquatic biota and fish habitat success, which reflect the health of Lac de Gras.

2.11.7 Climate Change and Lac de Gras

At the time of the original EA proposal, it was anticipated that the Mine would have a negligible effect on air quality (DDMI 1998d, CEAA 1999). Substances predicted to be release included particulates, nitrogen oxides (NOx), carbon monoxide (CO), sulphur dioxide (SO2), volatile organic compounds (VOC), methane (CH4) and trace constituents of other substances. Although the Mine would emit a number of substances into the air, ambient air quality objectives and occupational health criteria would not be exceeded.

The original EA also noted that the Mine would be a very minor contributor to Canada’s total emissions associated with global climate change. For example, the CO2, CH4 and N2O emissions from the Mine would be about 0.03%, 0.00048% and 0.022% respectively of Canada’s total for these three emissions (Government of Canada 1999). The Mine design had taken into account efficient use of energy and energy recovery to minimize emissions. Emissions from the Mine would primarily consist of carbon dioxide (CO2), with much smaller amounts of methane (CH4) and nitrous oxide (N2O) (DDMI 1998d). The responsible authorities conclude that the proposed project would not make a significant contribution to national or global emissions (Government of Canada 1999).

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Although the Mine is a minor contributor of greenhouse gases, it could be affected by global warming. Global climate change is of particular importance to the Mine because it is located in the Arctic region. Arctic regions are predicted to see greatest increases in temperature because of greenhouse gases. Increases in temperature in the Arctic have been recorded. Since 1976 a temperature increase of 0.75oC per decade has been recorded (Lim et al. 2001). According to Pienitz et al. (1997b), if global warming occurs, the chemistry of freshwater ecosystems will be greatly affected through, for example, changes in precipitation/evaporation ratios and runoff, duration of ice cover, and thickness of snow cover. The general physical and chemical cycles of lakes would be changed in ways that would affect lake productivity. It is also expected that a rise in annual Arctic temperatures could trigger an increase in ion content and nutrient levels leading to greater productivity. The populations and community structures of the Arctic waterbodies would be affected.

Since lakes in Arctic regions are extremely sensitive to climate changes (Michelutti et al. 2002, Ruhland et al. 2003), global warming could result in a change in baseline conditions at Lac de Gras. The lake could see increases in nutrient and ion concentrations that would definitely affect the AEMP.

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