The Arctic 'Great' Lakes of Canada and their fish faunas

JGLR-00988; No. of pages: 20; 4C: 8, 15 Journal of Great Lakes Research xxx (2015) xxx–xxx

Contents lists available at ScienceDirect

Journal of Great Lakes Research journal homepage: www.elsevier.com/locate/jglr

Review

The Arctic ‘Great’ Lakes of Canada and their fish faunas — An overview in the context of Arctic change James D. Reist, Chantelle D. Sawatzky ⁎, L. Johnson 1 Fisheries and Oceans Canada, 501 University Crescent, Winnipeg, MB R3T 2N6, Canada

a r t i c l e

i n f o

Article history: Received 29 April 2015 Accepted 28 September 2015 Available online xxxx Communicated by Pete Cott Index words: Large northern lakes Anthropogenic stressors Knowledge gaps Management

a b s t r a c t The present knowledge base and stressor status of 48 large (450 km2 or greater in area) Arctic lakes in Canada are reviewed. The lakes occur from the southern territorial boundaries to the northern-most extent of land in the Archipelago, and range in area from 440–31,153 km2. Productivities and species' complements established from proxy information indicate a declining trend from higher in the southwest Northwest Territories to lower in the northeast of Nunavut. Latitudinal and longitudinal variations in key present-day drivers (e.g., climate, surficial geology and associated nutrients) and historical factors (e.g., late Pleistocene peri-glacial processes) are likely responsible for these patterns. Despite their obvious significance in northern landscapes, knowledge is severely limited for all but a few of these lakes. Similarly, despite their remote locations, a wide range of stressors ranging from local in nature (e.g., industrial development) to pervasive and remotely driven (e.g., climate change) are very likely affecting the lakes and their associated fish faunas. Both the individual and cumulative effects of these stressors are nearly impossible to assess at present due to the dearth of knowledge. The risk of substantive effects occurring, however, is high. Comprehensive research in the near future is both desirable and required. Crown Copyright © 2015 Published by Elsevier B.V. on behalf of International Association for Great Lakes Research. All rights reserved.

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . Methods . . . . . . . . . . . . . . . . . . . . . . . . . Results . . . . . . . . . . . . . . . . . . . . . . . . . . Location . . . . . . . . . . . . . . . . . . . . . . Drainages . . . . . . . . . . . . . . . . . . . . . . Ecozone association and productivity inferences . . . . Overview of large lake descriptive parameters . . . . . General features of large northern lakes . . . . . . . . Glacial history . . . . . . . . . . . . . . . . . . . . Fishes as key faunal elements in large northern lakes . . Anthropogenic stressors . . . . . . . . . . . . . . . . . . Lake-specific stressors' overview . . . . . . . . . . . Urban centers . . . . . . . . . . . . . . . . . Roads . . . . . . . . . . . . . . . . . . . . Oil and gas development . . . . . . . . . . . . Mining . . . . . . . . . . . . . . . . . . . . Dams . . . . . . . . . . . . . . . . . . . . Contaminated sites . . . . . . . . . . . . . . Colonizations and introductions . . . . . . . . Pervasive stressors . . . . . . . . . . . . . . . . . . Long-range atmospheric transport of contaminants Climate variability and change . . . . . . . . . Cumulative impacts . . . . . . . . . . . . . . . . .

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⁎ Corresponding author. E-mail address: [email protected] (C.D. Sawatzky). 1 Deceased.

http://dx.doi.org/10.1016/j.jglr.2015.10.008 0380-1330/Crown Copyright © 2015 Published by Elsevier B.V. on behalf of International Association for Great Lakes Research. All rights reserved.

Please cite this article as: Reist, J.D., et al., The Arctic ‘Great’ Lakes of Canada and their fish faunas — An overview in the context of Arctic change, J. Great Lakes Res. (2015), http://dx.doi.org/10.1016/j.jglr.2015.10.008

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J.D. Reist et al. / Journal of Great Lakes Research xxx (2015) xxx–xxx

Protection, management, concerns and recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction The northern portions of Canada, similar to many areas throughout the global Arctic, are hydrologically rich environments consisting of hundreds of rivers and thousands of lakes crossing spatial scales from small and local (e.g., ephemeral streams, shallow potholes in permafrost tundra) to huge systems crossing many physiographic regions (e.g., Mackenzie River, Great Bear and Great Slave lakes) (Wrona et al., 2013). Key defining characteristics of these northern environments are the various elements of the cryosphere (i.e., the frozen phases of water) including permafrost, latitudinally varying seasonal ice formation, cover and dissolution, landscape precipitation loadings in winter as snow, and, in higher altitudes and latitudes, glacial ice and ice masses (AMAP, 2011). Northern aquatic systems are also dominated by high seasonal and inter-annual variability in incident radiation, thermal regimes, nutrient loadings and productivities that affect all physical, chemical and biological attributes (see individual papers in French and Slaymaker, 1993; Pielou, 1994). These fundamental system drivers vary substantively spatially with latitude and, to a lesser extent, with both altitude and longitude. Further, aquatic systems are embedded within a terrestrial landscape that itself varies in geomorphology with respect to basic surficial geology, soil characteristics, nutrients and associated vegetative production. All these factors affect the nature of processes and outcomes in hydrological systems as ‘downstream’ recipients of inputs from the land. These systems are geographically remote from the perspective and attention of most Canadians. Given the rate, nature and degree of changes projected for the Arctic, both from climate change and human activities (e.g., ACIA, 2005; Andrew, 2014) and the consequences of those changes to Canadians, development of wider understanding of lake systems in the Canadian Arctic is warranted. Canada is especially rich in surface fresh waters as a percentage of area (i.e., approximately 891,163 km2 or 8.9% in a total area of 9.985 × 106 km2; Statistics Canada, 2015). Among political divisions within Canada the percentage of areal freshwater coverage varies from b 0.1 (Prince Edward Island) to 15.4 (Quebec). The three northern territories are relatively water rich, Yukon (YT — 8052 km2, 1.7% of territorial area), Northwest Territories (NT — 163,021 km2, 12.1% of territorial area) and Nunavut (NU — 157,077 km2, 7.5% of territorial area), and collectively account for over one-third (328,150 km2, 36.8%) of Canada's areal surface water extent. The majority of surface waters primarily reflect the areal extent of lakes found within the respective areas. Accordingly, the Canadian Arctic, defined herein as territorial areas north of 60° North latitude (excluding northern Quebec; see below), is a region that is especially rich in freshwater lakes. The focus of this synoptic overview is to provide a background regarding the large lakes of the Canadian Arctic. Salient issues emerging from this overview include: 1) the dearth of basic knowledge regarding most of the lakes; 2) the absence of present research upon most; and, 3) despite their remote location, the individual and cumulative stressors most face are likely significant (and growing in intensity). Fertile fields of research await those wishing to venture north.

Methods This synopsis builds upon an unpublished manuscript developed in the early 1980s by one of us (LJ, ‘The Dimensions of the Canadian Arctic’). Further impetus derives from the thematic emphasis of this special issue, i.e., ‘large northern lakes’ (Cott et al., 2015a in this issue). Moreover, limited awareness by researchers and the public at large regarding both the

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size and number of large northern lakes is likely impeding the interest, and the development of knowledge, in regard to these large lakes. Literature and electronic information provide the majority of knowledge summarized herein. Despite efforts to acquire much of the existing information, it is likely that key elements or themes have been overlooked. In part, this results from a bias that pervades much of the northern ecological literature — primary publications on particular themes are lacking for all but a few of these lake systems. In many cases reports developed by consulting companies or government agencies examining particular aspects of a system have been done in support of environmental assessments associated with industrial development or fisheries and provide the only available information. These, however, are not always easily accessible (de Kerckhove et al., 2013); therefore, their use was limited in this review. A further complicating factor is that much of the research that does exist for larger lakes is relatively old, e.g., synoptic surveys for Great Slave Lake date from the 1950s (e.g., Rawson, 1950, 1956); and those for Great Bear Lake from the 1970s (e.g., Johnson, 1975a, 1975b, 1975c). Much of the research that has been conducted has focused upon the two ‘great’ northern lakes (Great Bear and Great Slave lakes) with limited effort being expended on other large lakes. In some cases it appears that no scientific research effort has been expended at all. A final bias also exists — due to their logistic tractability, most current research, particularly with respect to processes, is being conducted on smaller lake systems leaving the large lakes comparatively un-researched at present. We have defined the Canadian Arctic geopolitically (e.g., Angus, 2009), i.e., geographical extent of the three northern territories north of 60°N latitude. This definition represents a geographical sub-set of the Canadian North as viewed by most geographers (e.g., Vincent and Fick, 2000). Our delineation also aligns well with the guidelines for this issue (i.e., focus upon large lakes north of Lake Superior; Cott et al., 2015a in this issue). We limit the scope of this synopsis to lakes around 450 km2 or larger, however, estimates of area for many lakes vary widely (see Herdendorf 1982). The focus is upon individual lakes and does not include information from their wider drainages (i.e., inflowing rivers, upstream small lakes, outflowing rivers). We report upon 48 large lakes found in the Canadian Arctic. The comparatively large amount of information available for Great Slave Lake, and to a lesser extent for Great Bear Lake, could overwhelm a paper such as this. Accordingly, we have limited the scope of synoptic information for these lakes. Moreover, our geopolitical rather than ecological delineation of the Arctic results in the inclusion of many lakes that some would consider as ‘boreal’ or ‘sub-arctic’; location within particular ecological zones and geographic variation in lake attributes outlined below should clearly differentiate this association of the lakes.

Results Location Forty-eight large lakes in the Canadian Arctic meet our basic criteria for inclusion (Fig. 1, Table 1). These range across virtually the entire latitudinal zone possible, i.e., some straddle the NT or NU borders with the southern provinces at 60°N, whereas one is present at ~82°N just south of the limit of land on northern Ellesmere Island. Most (n = 44) are on the mainland with four present on islands of the Arctic Archipelago. Overall, 22 are found in NT and 26 in NU (3 in the Kitikmeot Region in the west, 4 in the Qikiqtaalik Region in the east, and 19 in the Kivalliq Region on the mainland). No lakes 450 km2 or larger are found in YT,



3 Northern Great Lakes

Northwest Territories 1. Artillery Lake 2. Aylmer Lake 3. Buffalo Lake 4. Clinton-Colden Lake 5. Colville Lake 6. Lac de Gras 7. Lac de Bois 8. Faber Lake 9. Great Bear Lake 10. Great Slave Lake 11. Hottah Lake 12. Husky Lakes 13. Kasba Lake 14. Lac la Martre 15. Mackay Lake 16. Nonacho Lake 17. Point Lake 18. Selwyn Lake 19. Snowbird Lake 20. Tathlina Lake 21. Trout Lake 22. Wholdaia Lake

Nunavut 23. Aberdeen Lake 24. Amadjuak Lake 25. Angikuni Lake 26. Baker Lake 27. Contwoyto Lake 28. Dubawnt Lake 29. Ennadai Lake 30. Ferguson Lake 31. Garry Lake 32. Hall Lake 33. Lake Hazen 34. Kamilukuak Lake 35. Kaminak Lake 36. MacAlpine Lake 37. Maguse Lake 38. Mallery Lake 39. Napaktulik Lake 40. Nettilling Lake 41. Nueltin Lake 42. Princess Mary Lake 43. Qamanirjuaq Lake 44. South Henik Lake 45. Tebesjuak Lake 46. Tehek Lake 47. Tulemalu Lake 48. Yathykyed Lake

Fig. 1. The 48 large northern lakes considered herein. Red dots indicate population centers, and the black line indicates continuous tree line. Lake names are from official gazeteers or similar sources; local names or spellings may vary. (For interpretation of the references to color in this figure caption, the reader is referred to the web version of this article.)

although a few in this territory approach several hundred km2 in size. Most mainland large lakes are found well inland in central and southern NT and western areas of mainland NU (i.e., Kivalliq Region). Much of this region is sometimes referred to as the ‘Barren Lands’ in reference to being north of the tree line (Pielou, 1994). Indirect drainage to marine areas is the norm for these and they are often long ‘river’ distances from the sea. Three mainland lakes, however, can be considered coastal — nos. 12, 26 and 32 in Fig. 1. The four lakes on the archipelago islands (nos. 24, 30, 33 and 40) are also geographically proximate to marine systems, however, nos. 24 and 40 have longer ‘river’ distances to the sea than do nos. 30 and 33. The 48 large Arctic lakes have a total surface area of 107,825 km2, i.e., 12.1% of all surface waters (891,163 km2) in Canada. The 22 lakes found in the Northwest Territories total 75,879 km2 in area or 46.5% of the surface waters in the NT (163,021 km2) with the two Arctic ‘great’ lakes accounting for 59,723 km2 (36.6% of the territorial lake area total). The 26 lakes in Nunavut have a total surface area of 31,946 km2 (20.3% of all surface waters in NU, 157,077 km2). These large lakes are clearly a significant aquatic resource in Canada.

Drainages Ten of the large lakes are within the Arctic Ocean Seaboard drainage (nos. 12, 6, 5, 7, 39, 17, 27, 36, 30, 33) (Fig. 2A). One large lake (no. 31) is associated with the Back River drainage, a large, complex central Arctic river draining into the marine channels of the Arctic Archipelago. Thirteen large lakes are associated with the Thelon River drainage (nos. 13, 22, 19, 29, 25, 34, 48, 47, 28, 45, 38, 42, 23), a large, complex system of the interior Kivalliq area that ultimately drains into Hudson Bay. Ten other lakes drain directly to the Hudson Bay system via coastal rivers (nos. 41, 44, 37, 35, 43, 26, 32, 40, 24, 46). Finally, 14 lakes drain into the Mackenzie River basin either directly or via intervening drainages (nos. 18, 1, 2, 4, 15, 16, 3, 10, 20, 21, 14, 8, 11, 9) with ultimate outflow into the Beaufort Sea of the western Arctic.

Ecozone association and productivity inferences Canada is divided into 15 ecozones. Ecozones are large-scale integrations of geomorphology, types and nature of biodiversity, climate drivers, and gross estimators of productivity (Andrew et al., 2013). There are substantive latitudinal gradients in key climate parameters such as radiation, temperature and humidity for Canada (Liu et al., 2002; Andrew et al., 2011) with decreasing productivity in more northerly ecozones. There is also a declining productivity gradient from western to eastern areas in the Canadian Arctic. Within larger ecozones there may be a similar phenomenon (see below), but there also may be longitudinal variation in parameters and productivity. Such gradients reflect climate effects and geomorphology as the ecozone concept is primarily reflective of terrestrial biological systems. Lakes contained within the ecozone are subject to inputs from the landscape and the same climate drivers. In the absence of measures of lake-specific productivity parameters, terrestrial analogs can provide general information and the basis for inferences regarding relative productivity, and are so used herein. While logically linked, however, productivity in aquatic systems may not be directly associated with that of the surrounding ecozone; for example, Samarasin et al. (2014) indicate that fish biomass and diversity, at least in smaller northern lakes is, respectively, greater and higher than expected based upon adjacent ecosystems. Accordingly, some of the generalities and conclusions outlined require direct verification through new research on these large lakes. The 48 large lakes are distributed among four ecozones (Fig. 2B): Northern Arctic (n = 7 lakes), Southern Arctic (18), Taiga Shield (14) and Taiga Plains (9) (Table 1). In terms of average modeled terrestrial net primary productivity, the ecozones range from 0 (standard deviation (SD) = 2) g C/m2 for the Northern Arctic, to 15 (SD = 24) for Southern Arctic, 57 (SD = 61) for the Taiga Shield and 171 (SD = 126) for the Taiga Plains (Liu et al., 2002). There is a clear latitudinal gradient in production from south (higher) to north and also from west (higher) to east in the terrestrial areas surrounding these large Arctic lakes. Most of the lakes in extreme southeastern NT, mainland central and


4

Name (Fig. 1 number)

Location

Area km2 Elevation Area km2 Area km2 (m) (Johnson) (Johnson) (World (Global LakeDatabase) Lakes & Wetlands DB)

Elevation (m) (World Lake Database)

Drainage Elevation (m) (Global Lakes & Wetlands DB)

Physiographic region

Ecozone

Position relative to tree Line (+ = south of, − = north of)

Northwest Territories Artillery (1) 63.15,−107.87 552

536

545

365

365

359

Mackenzie

Canadian Shield

Taiga Shield

−/ +

Aylmer (2)

64.08,−108.50 847

808

790

375

375

366

Mackenzie

Canadian Shield

−

Buffalo (3)

60.22,−115.50 614

611

599

265

265

264

Mackenzie

Interior Plains

Southern Arctic/Taiga Shield Taiga Plain

Clinton-Colden 63.92,−107.48 736 (4)

596

649

375

375

366

Mackenzie

Canadian Shield

−

Colville (5)

67.17,−126.00 456

–

433

245

–

293

Interior Plains

de Gras (6)

64.50,−110.50 632

633

713

416

396

454

Canadian Shield

Southern Arctic

−

des bois (7)

66.83,−125.15 469

–

460

297

–

299

Interior Plains

Taiga Plain

+

Faber (8)

63.93,−117.25 440

–

430

213

–

213

Arctic Ocean Seaboard Arctic Ocean Seaboard Arctic Ocean Seaboard Mackenzie

Southern Arctic/Taiga Shield Taiga Plain

65.83, −120.75

31,153

30,530

186

186

157

Mackenzie

Great Slave (10)

61.50,−114.00 28,570

–

27,816

156

–

158

Mackenzie

Hottah (11)

65.07,−118.50 917

839

955

180

180

221

Mackenzie

Canadian Shield

Taiga Shield/Taiga Plain Taiga Plain/Taiga Shield Taiga Plain/Taiga Shield/Boreal Plain Taiga Shield/Taiga Plain

+

Great Bear (9)

Interior Plains/Canadian Shield Interior Plains/Canadian Shield Interior Plains/Canadian Shield

Husky Lakes (Eskimo) (12)

67.52,−135.14 1933

–

1146

North: 0.3 South: 2

–

4

Arctic Ocean Seaboard

Canadian Shield

Southern Arctic

−

Kasba (13)

60.30,−102.12 1342

1320

1335

336

336

335

Thelon

Canadian Shield

Taiga Shield

+

la Matre (14)

63.25,−117.92 1777

–

1684

265

–

265

Mackenzie

Interior Plains

Taiga Plain

+

31,153

Comments Depth Depth — maximum — mean (m) (m)

Subsistence and sport fisheries Sport fishery

+

2

+ 12

56

+

71.7

446

+

41

614

+

18.9

69.5

Est. 17

Occasional subsistence fishery; Partially within Wood Buffalo National Park

Subsistence and sport fisheries Sport fishery; Diamond mining Subsistence and sport fisheries Subsistence and sport fisheries

Subsistence and sport fisheries; Lake Trout and Lake Whitefish commercial fishery in the late 1960s and early 1970s All inner and outer basins (calculate inner area only); Subsistence fishery; Oil and gas facility nearby Lake Trout and Lake Whitefish commercial fishery 1963 and 1968; Subsistence and sport fisheries Subsistence and sport fisheries; Lake Trout, Lake Whitefish and Northern Pike commercial fishery 1969–72



Table 1 Large Arctic lakes and their key parameters and attributes.




Ecozone

431

431

426

Mackenzie

Canadian Shield

Taiga Shield/Southern Arctic

847

319 ?

354

353

Mackenzie

Canadian Shield

Taiga Shield

+

593

–

375

375

–


Canadian Shield

−/+

60.08,−104.42 717

593

607

398

398

393

Mackenzie

Canadian Shield

Southern Arctic/Taiga Shield Taiga Shield

Snowbird (19)

60.68,−102.93 505

490

499

359

359

358

Thelon

Canadian Shield

Taiga Shield

+

Tathlina (20)

60.55,−117.53 572

573

572

280

280

277

Mackenzie

Interior Plains

Taiga Plain

+

Trout (21)

60.58,−121.32 505

505

495

503

503

494

Mackenzie

Interior Plains

Taiga Plain

+

Wholdaia (22)

60.72,−104.17 679

609

1067

364

364

364

Thelon

Canadian Shield

Taiga Shield

+

Nunavut Aberdeen (23) Amadjuak (24)

64.50,−99.00 64.92,−71.13

1101 3116

1100 3060

1128 3034

80 113

80 113

76 112

Thelon Hudson Bay Seaboard

Canadian Shield Canadian Shield

Southern Arctic Northern Arctic

− −

Angikuni (25) Baker (26)

62.20,−99.98 64.17,−95.50

510 1888

438 1780

562 1780

257 2

257 2

256 2

Thelon Hudson Bay Seaboard

Canadian Shield Arctic & Subarctic/Canadian Shield

Taiga Shield Northern Arctic/Southern Arctic

−/ + −

Contwoyto (27) Dubawnt (28) Ennadai (29) Ferguson (30)

65.65,−110.72 958

932

1092

445

564

444

Canadian Shield

Southern Arctic

−

63.13,−101.47 3833 60.97,−101.33 681 62.92,−96.88 588

3630 668 562

3628 706 573

236 311 11

236 311 113

235 310 11

Arctic Ocean Seaboard/Back Thelon Thelon Arctic Ocean Seaboard

Canadian Shield Canadian Shield Arctic & Subarctic

Southern Arctic Taiga Shield Northern Arctic

− + −

Garry (31)

65.97,−100.30 976

917

787

148

148

150

Back

Canadian Shield

Southern Arctic

−

Hall (32)

68.68,−82.28

–

475

6

–

6

Hudson Bay

Arctic & Subarctic

Northern Arctic

−

Location

MacKay (15)

63.92,−110.42 976

976

980

Nonacho (16)

61.98,−109.47 785

697

Point (17)

65.25,−113.07 702

Selwyn (18)

492



−/+

14

40

+

Subsistence and sport fishery; Lake Trout and Lake Whitefish commercial fishery 1965–67; Diamond mining Lake Trout and Lake Whitefish sporadic commercial fisheries 1958–71; Sport fishery Subsistence fishery

Lake Trout and Lake Whitefish commercial fishery 1975–77 and 1979; Subsistence and sport fisheries Subsistence and sport fisheries Walleye commerical fishery closed; Subsistence fishery Subsistence and sport fisheries Subsistence and sport fisheries

1.5

Occasional sport fishery; Small commercial fishery for char in the late 1970s to early 1980s 230





Lake Trout and Lake Whitefish harvested for local sale; Lake Whitefish and Cisco spp. commercially fished in 1975 Mining Sport fishery

6.1

9.1

Commercial fishing char, Lake Whitefish, Lake Trout 1962–1975 Lake Trout and Lake Whitefish commercial fishery 1975–76 Commercial, (continued on next page) 5

6


Location





Ecozone



Seaboard Hazen (33)

81.80,−71.02

541

542

–

280

158

–


Arctic & Subarctic

Northern Arctic

−

Kamilukuak (34) Kaminak (35)

62.37,−101.67 635

629

672

266

266

266

Thelon

Canadian Shield

Taiga Shield

+

62.17,−95.00

554

736

53

53

47

Hudson Bay Seaboard

Canadian Shield

Southern Arctic

−

MacAlpine (36) Maguse (37)

66.53,−102.75 488

–

466

176

–

175

Canadian Shield

Southern Arctic

−

61.62,−95.17

–

–

–

–

–

Canadian Shield

Southern Arctic

−

Mallery (38) Napaktulik (39) Nettilling (40)

63.98,−98.38 479 66.33,−113.00 1080

– 1030

445 1014

158 381

– 381

135 403

Canadian Shield Canadian Shield

Southern Arctic Southern Arctic

− −

66.48,−70.33

5543

5050

5065

29

30

30

Arctic Ocean Seaboard Hudson Bay Seaboard Thelon Arctic Ocean Seaboard Hudson Bay Seaboard

Canadian Shield

Northern Arctic

−

Nueltin (41)

60.50,−99.50

2279

2030

2012

278

278

277

Hudson Bay Seaboard

Canadian Shield

Taiga Shield

+

Princess Mary (42) Qamanirjuaq (43) South Henik (44)

63.95,−97.58

523

524

468

116

116

115

Thelon

Canadian Shield

Southern Arctic

−

62.95,−95.77

549

–

–

92

–

–

Canadian Shield

Southern Arctic

−

61.45,−97.37

513

513

570

184

184

184

Hudson Bay Seaboard Hudson Bay Seaboard

Canadian Shield

Taiga Shield

+

Tebesjuak (45) 63.77,−99.00 Tehek (46) 64.92,−95.63

575 482

500 –

489 491

146 133

146 –

144 155

Canadian Shield Arctic & Subarctic

Southern Arctic Northern Arctic

− −

Tulemalu (47)

62.97,−99.42

668

663

657

279

279

279

Thelon Hudson Bay Seaboard Thelon

Canadian Shield

−

Yathkyed (48)

62.67,−97.97

1448

1330

1320

141

141

101

Thelon

Canadian Shield

Southern Arctic/Taiga Shield Southern Arctic/Taiga Shield

601

1399

−

85

267

subsistence and sport fisheries–char Occasional sport fishery; Entirely within Quttinirpaaq National Park

Lake Trout and Lake Whitefish commercial fishery 1967–75

20

132

Formerly Takiyuak Lake Commercial char fishery 1974–1977, 1990, opened for winter fishing in 1990 Lake Trout and Lake Whitefish commercial fishery 1949–1969; Sport fishery

aka Kaminuriak 18

Lake Trout and Lake Whitefish commercial fishery in 1970; Sport fishery Gold mining

Sport fishery



Table 1 (continued)


southern NU north and south of the tree line, and northeastern NT along the margin of the tree line, are all in areas of low simulated terrestrial net primary productivity (i.e., ~ 0.05 to 0.1 kg C/m2/yr) (Liu et al., 2002; Andrew et al., 2011). Those farther north are in areas of even lower terrestrial productivity (i.e., 0.01 kg C/m2/yr). In contrast, lakes in the Mackenzie River drainage basin, mostly associated with the Taiga Plains, are in areas of projected net primary terrestrial productivities of 0.1 to 0.3 kg C/m2/yr. This includes the two great lakes in this region. Although elevation affects productivity (Andrew et al., 2011), the relatively small overall differences in this parameter among the lakes (Table 1) suggest its effects are limited and likely small in comparison to other factors (e.g., very low elevations for some lakes equate to proximity to marine systems with ameliorating influences to local climate and anadromous fish productivity (see below)). Direct productivity estimates for most lakes are lacking and the few estimates that are available are relatively old. Great Slave Lake, which spans two terrestrial ecozones (Fig. 2B), provides an example of contrasting productivities associated with different ecozones. Primary production in the east arm (Taiga Shield ecozone) is around 10 g C/m2/yr (Schindler, 1972) whereas that for the western basin (Taiga Plains ecozone, with significant inputs from the Boreal Cordillera via the Slave River) is around 30 g C/m2/y (Fee et al., 1985). Similarly, latitudinal variation of productivity within an ecozone is apparent when comparing Great Bear and Great Slave lakes. Primary production in the eastern area of Great Bear Lake (also in the Taiga Shield ecozone, but approximately four degrees of latitude north of east arm Great Slave Lake), is lower (4 g C/m2/yr) than that in the east arm of Great Slave Lake (10 g C/m2/y; Schindler, 1972). Primary productivities ultimately translate to production at higher trophic levels such as fishes. Productivities of these are generally expected to follow similar geographic trends modified by species' complements and local factors (see below). Marine-derived nutrients are transported into fresh water via migratory fishes that use both habitats during life history. Pacific salmons, semelparous species that die after reproduction and hence contribute their carcasses and gametes to the systems, provide the best example (Schindler et al., 2003) for southern systems. Most migratory salmonids in Arctic systems are iteroparous (i.e., live after reproduction; Reist and Bond, 1988) and overwinter in fresh waters. They typically exhibit 3–5 cycles of summer marine feeding excursions and freshwater reproduction and overwintering over their lifetimes. Thus, while individual marine-derived subsidies to northern lakes may be low annually, cumulatively they do increase productivity (Swanson et al., 2010, 2011) especially in nutrient-limited smaller Arctic lakes. How these inputs may scale and affect larger lakes is unknown. Similarly, seabirds transport marine-derived nutrients and contaminants to Arctic lakes, and colonial nesting habits of some may make this vector a significant source (Michelutti et al., 2010) in coastal lakes. In this context, lakes proximate to marine systems by air (seabirds) and/or river distances (e.g., nos. 12, 24, 26, 30, 32, 36 and 40, and possibly 33) likely experience higher than expected local production due to this transport which offsets expectations based upon location and ecozone association. Incremental production, in turn, may be reduced to some extent as a result of summer climate effects — proximity to the marine environment generally cools nearby land areas particularly in the ice- and cold marine-water dominated Arctic. Overview of large lake descriptive parameters Estimates of key parameters (e.g., area, elevation) vary among sources, and in many cases are not directly documented (e.g., mean and maximum depth) (Table 1; International Lake Environment Committee Foundation World Lake Database, http://wldb.ilec.or.jp/; accessed 15 April 2015; Herdendorf 1982). Estimated area ranges from 440 km2 (no. 8) to 31,153 km2 (no. 9). Most large Arctic lakes are under 1000 km2 (n = 34), with 12 having areas between 1000 and 5000 km2. As noted above, the two ‘great’ lakes in the region have

7

areas in excess of 25,000 km2. These values are comparatively similar to those of more familiar large southern lakes (e.g., Lake Winnipeg – 24,154 km2, Lake Ontario – 18,960 km2, Reindeer Lake – 6500 km2 and Lake Nipigon – 4848 km2). Elevations range from ~ 2 m (no. 12) to ~ 503 m (no. 21). Where estimated, mean depths range from 1.5 m (no. 20) to 85 m (no. 33) (9 estimates), and maximum depth ranges from 2 m (no. 3) to 614 m (no. 10) (11 estimates). In many cases the estimates are likely biased due to limited sampling. Encompassed within the Arctic as defined here, are three of the top 30 largest, by area, lakes of the world (excluding the Caspian and Azov seas, and the under-ice Lake Vostok in Antarctica) — Great Bear (ranked 7th at 31,153 km2), Great Slave (9th at 28,570 km2) and Nettilling (28th at 5543 km2) (Table 1; International Lake Environment Committee Foundation World Lake Database, http://wldb.ilec.or.jp/; accessed 15 April 2015). Dubawnt (3833 km2) and Amadjuak (3116 km2) follow closely. With respect to recorded maximum depths, Great Slave at 614 m ranks 6th deepest in the world and Great Bear at 446 m ranks 29th. Volumetrically, Great Bear ranks 8th (2236 km3), Great Slave 11th (1580 km3) and Nettilling 29th (114 km3). All these parameters are generally poorly estimated for most lakes, however, they do provide clear indications regarding the significance of some of the Arctic lakes considered herein. As exemplified by the absence of key parameters for some lakes, the variation in some parameter estimates (e.g., Area columns, Table 1), and low confidence in some estimates, considerable gaps in knowledge exist for most key physical parameters for these lakes. Although not enumerated here, gaps regarding chemical and basic biological parameters are substantive, all of which reflect the paucity of research regarding most large Arctic lakes. General features of large northern lakes All large lakes considered herein are, and have been, affected by several present-day and historical large-scale factors. Many of these are pervasive throughout the area. The dominance of the cryosphere both annually and over the longer term is a fundamental factor influencing northern large lakes and their associated basins. Individual cryospheric components (i.e., permafrost, ice cover, significant precipitation as snow, glacial inputs) are either perennially present or seasonally relevant for much of the year with increasing influence in colder areas. Permafrost creates an impermeable barrier to water penetration into the sub-surface strata particularly in tundra environments, thus generally encourages surface water flows across northern landscapes and into the larger rivers and lakes in the area. Accordingly, the proportion of nutrient and contaminant transport via surface drainage patterns is likely more significant in the north than in southern permafrost-free environments. Ice cover is significant from several perspectives: 1) limitation of wind-driven mixing processes for much of the year (i.e., ~6–11 months of the year depending upon lake latitude); 2) diversion of substantive amounts of spring radiant energy into melting and thus away from production processes; 3) albedo effects (i.e., reflection of incident radiation limits its use for in-lake biological or physical processes); and 4) gas exchange (Vincent et al., 2013). Ice thickness, which varies latitudinally between 1 and 2 or more meters (Woo, 1993), also modifies many physical and chemical processes particularly light limitation and diversion of radiant energy to melt. Precipitation, mostly as snow, interacts with ice (when present) to further increase reflection and limit incident radiation transmission into the water body thereby influencing production (Welch et al., 1987). The extensive winter season and limited summer heating result in generally cold temperatures throughout lakes in northern locales. Generally, even the largest tend to be isothermal with water temperatures near 3 °C or lower over much of their depths (Vincent et al., 2008 and references therein). Exceptions include near surface waters (e.g., no. 9 summer water temperatures vary between 6 °C and 16 °C in the


8


A.

Legend Drainages Arctic Ocean Seaboard Back Hudson Bay Seaboard Mackenzie Thelon

B.

Legend Ecozones Arctic Cordillera Boreal Cordillera Boreal Plain Boreal Shield Hudson Plain Montane Cordillera Northern Arctic Pacific Maritime Southern Arctic Taiga Cordillera Taiga Plain Taiga Shield

Fig. 2. A) Drainage basins of the Northwest Territories and Nunavut and B) ecozones of northern Canada.

upper 20 m; Blanken et al., 2000) and embayments subject to winter ice and summer heating. Development of strong thermoclines and/or thermally driven seasonal overturn generally is, therefore, not a feature of northern large lakes (e.g., no. 40; Oliver, 1964); the exceptions may be those that are smaller in area, shallower and near the southern margin of our region (e.g., nos. 3 and 20). Perhaps the most significant over-arching general feature of northern lakes is the annual cycle of incident radiation that is affected by cumulative daily durations and angle of incidence, both of which are correlated with latitude. Lakes on the Arctic Circle (66°33′N latitude)

experience 30 days of 24 h of exposure centered on the summer solstice (June 21). During summer those farther north will experience longer periods with 24-hour incident radiation. Annual periods of reduced or absent incident radiation occur reciprocally during winter. Accordingly, the timing of primary production is highly pulsed seasonally, however, a significant amount typically occurs under ice early in the polar spring (Vincent et al., 2008). The angle of incidence also affects the intensity of radiation reaching lake surfaces (i.e., intensity is the sine of the incident angle), thus lakes farther north (e.g., lake no. 33 at ~82°N) experience only about 17% of the radiative intensity than do lakes at the



equator. Lakes at the southern margin of our area of consideration (60°N) experience about 50% and those at the northern continental margin (70°N) about 34% of equatorial intensity. Thus, the interaction of incident angle with daily duration ultimately affects heating and production in these lakes. Glacial history At Wisconsinan glacial maximum, approximately 18,000 years before present (i.e., 18 ka BP), virtually the entire area of interest here and all of the lakes considered were covered by extensive ice masses (Dyke et al., 2002). Exceptions include the following: 1) the northwestern portion of the Yukon and a central southeastern corridor between the Laurentide (main continental) and Cordilleran (coastal montagne) ice masses (these two areas were contiguous with the Beringian refugium), and 2) areas of the outer Mackenzie Shelf exposed by sea-level lowering and much of Banks Island (these areas may have constituted sub-refugia for some biota) (Pielou, 1991; Dyke et al., 2002). The presence of large, proglacial lakes at this time are known only from northwestern Yukon and they flowed westwards into the Beringian Yukon River system. Degradation of the Laurentide ice sheet was mostly northwards until around 13 ka BP at which time small, proglacial lakes existed along the ice mass margins. At 11 ka BP an extensive series of proglacial lakes provided an almost continuous connection from the western edge of present-day Lake Superior west and northwards to the nascent Mackenzie River thence to the Beaufort Sea (i.e., Mississippian and Missourian refugia were linked to the north). Present-day great lakes (Laurentian including Superior north to and including Great Bear Lake) remained ice covered at this time. By 10 ka BP, the marginal proglacial lakes became more extensive and better connected essentially as one large system extending from the area of present-day Lake Superior to Great Bear Lake. Ice mass degradation during this and subsequent periods was northeastwards with the large proglacial lakes generally following the ice margin and shifting in both areal coverage and connectivity. By around 8 ka BP separate protolakes were formed in Great Bear, Great Slave and Lake Athabasca basins, and also in the central Keewatin region of Nunavut. Extensive proglacial lakes covered most of Manitoba (Glacial Lake Agassiz) and northcentral Ontario east to Quebec (Glacial Lake Barlow-Ojibway) with the glacial lakes being contiguous. The Laurentian Great Lakes including Nipigon had assumed their present-day limits at this time. Marine inundations covered the east-central portion of the Arctic Archipelago and ice masses were contiguous from northern Ontario and Quebec westwards to the Keewatin area and north to Baffin Island. By 7 ka BP, present-day lakes Winnipeg, Manitoba and Reindeer were formed; remnant ice masses existed in the northern Keewatin margin with extensive proglacial lakes along their western margin and marine inundations from a now ice-free Hudson Bay along the east. Ice domes persisted on Baffin Island, Foxe Basin of northern Hudson Bay, the Melville Peninsula and northern Quebec. By 5 ka BP virtually all present-day drainages and lake margins were established with the exception of southern and central Baffin Island where ice remained in highland areas. Marine incursions also persisted around the coast of Hudson and James bays and Foxe Basin at this time (Pielou, 1991). Several key emergent present-day consequences from glaciation and de-glaciation dynamics are relevant to the large northern lakes. Most lakes originated from either/both glacial lakes as ice or water scour or pro-glacial lakes that were much larger than the present-day lakes, particularly those associated with bedrock geologies (i.e., eastern and northern areas). Some that originated in sedimentary landscapes have glacial origins, however, thermokarst processes appear to figure prominently in their recent history (Vincent et al., 2013). The immense pro-glacial lakes often persisted for long periods of time (e.g., several thousand years) before present-day smaller derivative lakes were formed. Postglacial re-bound processes have affected lake formation virtually throughout the entire area and are still occurring in northeasterly

9

areas. For some lakes, several post-glacial ‘benches’ are present indicating past shorelines during different phases of their evolution. In this context, the majority of Canadian large Arctic lakes share similarities with other large Arctic lakes including Taimyrskoe, Khanataiskoe and Pyasina of Russia and Inarijarvi of northern Finland (Ryanzhin et al., 2010). Only one lake (Husky Lakes) likely results from impoundments of coastal lagoons due in part to isostatic re-bound of the surrounding landscapes (Ryanzhin et al., 2010). Thus, Husky Lakes shares some similarities with Selawik and Teshukpuk lakes of north slope Alaska (e.g., see Ryanzhin et al., 2010 for different lake-origin types although some classifications therein are erroneous), to which thermokarst processes have contributed. Unlike Lake Imandra (Russia), Illiamna and Becharof lakes (Alaska Peninsula), and Thingvallavatn (Iceland), no evidence exists for any large Arctic Canadian lake originating from tectonic processes. Most present-day distinct lakes in our area were contiguous at some point during their history. Ice mass degradation had both a northern and a northeastwards directional component to it; although uncertain, much of the drainage appeared to be northwards along the ice margin, however, the extensive build-up of water in Glacial lakes Agassiz and Barlow-Ojibway suggest significant impoundment for long periods rather than regular drainage (Pielou, 1991; Dyke et al., 2002). This is further supported by the catastrophic drainage of the Agassiz–Barlow– Ojibway complex east and southwards around 7.7 ka BP. Similar local connections and/or catastrophic drainages occurred in areas to the west and northwards (e.g., in the northern prairie provinces glacial lakes Agassiz and Peace drained catastrophically about 9.9 ka BP; Rempel and Smith, 1998). The very large proglacial or glacial lakes fragmented into a number of large lake basins that are present today in some areas (e.g., southern Nunavut); others formed very large present-day lakes (e.g., Great Slave and Great Bear lakes) with multiple basins and/or embayments. Generalized ages of the present-day lakes thus range from around 10,000 years or so (most western lakes), 7–8000 years or so (most mainland lakes in southeastern Northwest Territories and Nunavut), to 6000 years or less (lakes on eastern Nunavut islands). Biotic colonizations of these areas were from multiple refugia, and for fishes, include the following sources (Crossman and McAllister, 1986; Lindsey and McPhail, 1986): Mississippian, Missourian, possibly Pacific, Beringian (and sub-refugium Nahannian); perhaps Banks Island for some species; and Atlantic for others (e.g., Arctic char, Salvelinus alpinus in the east). Colonizations, especially for taxa of greater vagility, were likely multiple (times and/or sources) into some areas and also may have been stepwise. For fishes, pathways of colonization included freshwater routes via glacial lakes and rivers including drainage reversals and headwater captures, and seawater corridors for anadromous species. Thus, de-glaciation processes and events both created the lakes and also determined the nature, speed and species' complements of the developing biota that were able to colonize the newly formed habitats. Fishes as key faunal elements in large northern lakes As noted, there is a lack of key limnological information for most large Arctic lakes. This is also true regarding documentation of fish occurrences in many of the lakes. The data (Table 2) are likely biased and incomplete (e.g., targeted sampling for larger fished species, smaller-bodied species missed due to gear used). Given these caveats, several generalizations can be made. Fish species occurrence data do not appear to exist for 11 (23%) of the lakes. Fifteen (31%) lakes have 1–5 species reported, 13 (27%) have 6–10 species reported and 6 (13%) have 11–15 species reported. For most, especially those with fewer than 10 species reported, these very likely represent under-estimates. That is, the actual species complement is likely higher, with some small-bodied groups (e.g., cyprinids, trout-perch, sticklebacks and sculpins) missed due to


10

3

Name

Total N Species in Lake

1

Primary Life History 2

Status

A R L M

G O L D

L K C H

E M S H

S P S H

F L C H

L N D C

P R D C

F N D C

F T M N

P E A M

L N S C

W H S C

N R P K

P N S M

R N S M

C I S C 4

A R C S

L K W H

B R W H

L S C 6 S

S H C 4 S

C M S L

C H S L

R N T R

S C S 7 L

R N W H

P Y W H

A R C H

L K T R

I N C O

A R G R

T R P R

B U R B

B R S T

T H S T

N N S T

S L S C

S P S C

D P S C

Y L P R

W A L L

A

F

F

F

F

F

F

F

F

F

F

F

F

F

F

A

F

A

F / A

A

A / F

F

A

A

F

A

F

F

A

F

A

F

F

F

F

A

F / A

F

F

F

F

F

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

V

I

V

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

x

x

x

x

x

x

x

x

Northwest Territories Artillery (1) Aylmer (2)

7

Clinton-Colden (4)

6

Colville (5)

8

de Gras (6)

2

des Bois (7)

4

Faber (8)

3

Great Slave (10) Hottah (11) Husky Lakes (Eskimo) (12)

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x x

9

x

x

x

x

9

x

x

14

x

x

MacKay (15)

3

x

x

x

x

x

x x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

V x

x

x

x

x x

x

x

V x

x

x x

x

Selwyn (18)

3

x

Snowbird (19)

9

x

x

x

x

Tathlina (20)

7

x

x

x

x

x

x

x

x

x

x

14

x

9

x

x

x

x x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x x

0

Angikuni (25)

6

Baker (26)

2

Contwoyto (27)

8

Dubawnt (28)

10

Ennadai (29)

0

Ferguson (30)

3

x

x

x

x x

x

x

x

x

x

x x x

x

x

x

x

x x

x

x

x

x

x

x

x x

x

x

x

x

x

x

x

x

x

x x

x

x

x x

0

Amadjuak (24)

x

x

Nunavut Aberdeen (23)

x

x

x

x

x

x

x x

x

x

x

x x

x

x

x

x

x

x

13

x

x

x

x

12

x x

x

x

x

Point (17)

Wholdaia (22)

x

x

x

x

x

x

Nonacho (16)

Trout (21)

x

x

x

13

x

x

x x

x

x x x

x

x

x

x

x

26 33

x x

la Martre (14)

Kasba (13)

x

2

Buffalo (3)

Great Bear (9)

x

7

x

x

x

x

x

x

x

x

x

x

x

x

x

x



Table 2 Documented fish species occurrences in large Arctic lakes. Four-letter common name abbreviations are defined below. Sources for the Northwest Territories include Scott and Crossman (1973), McPhail and Lindsey (1970), Sawatzky et al. (2007), and Karen Dunmall (University of Manitoba and Fisheries and Oceans Canada, personal communication, 2015). Sources for Nunavut include Scott and Crossman (1973) and Stewart (1994).

Total N Species in Lake

1

Primary Life History 2

Status

A R L M

G O L D

L K C H

E M S H

S P S H

F L C H

L N D C

P R D C

F N D C

F T M N

P E A M

L N S C

W H S C

N R P K

P N S M

R N S M

C I S C 4

A R C S

L K W H

B R W H

L S C 6 S

S H C 4 S

C M S L

C H S L

R N T R

S C S 7 L

R N W H

P Y W H

A R C H

L K T R

I N C O

A R G R

T R P R

B U R B

B R S T

T H S T

N N S T

S L S C

S P S C

D P S C

Y L P R

W A L L

A

F

F

F

F

F

F

F

F

F

F

F

F

F

F

A

F

A

F / A

A

A / F

F

A

A

F

A

F

F

A

F

A

F

F

F

F

A

F / A

F

F

F

F

F

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

V

I

V

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

x

x

Garry (31)

2

Hall (32)

1

x

Hazen (33)

1

x

Kamilukuak (34)

0

Kaminak (35)

2

MacAlpine (36)

0

Maguse (37)

8

Mallery (38)

0

Napaktulik (39)

0

Nettilling (40)

3

Nueltin (41)

12

Princess Mary (42)

0

Qamanirjuaq (43)

1

South Henik (44)

5

Tebesjuak (45)

0

Tehek (46)

0

Tulemalu (47)

0

Yathkyed (48)

0

Species in N Lakes

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x x

x

x x

x

x

x

x

x x

x

13

12

x

x

1

2

7

1

1

1

1

1

1

1

1

19

9

17

2

1

16

3

27

4

4

2

2

1

1

1

19

1

8

31

8

20

4

17

1

1

1

3

1

10

J.D. Reist et al. / Journal of Great Lakes Research xxx (2015) xxx–xxx 11


3

Name

12


the specialized gear and effort required for capture. In contrast, both great lakes have been reasonably well-studied with 26 species known to occur in Great Bear Lake and 32 in Great Slave Lake. Note these counts include records of occasional vagrants (3 and 1, respectively) but introduced taxa are excluded. Occurrence of particular species in the various lakes represents a sub-set of the taxa present in the respective territories. There are 42 native species in NT with a further five episodically present as vagrants and one introduced (Sawatzky et al., 2007). In comparison, in NU 20 freshwater and anadromous species occur with four additional ones as vagrants (Scott and Crossman, 1973; Reist, unpubl. data). Fish occurrence in the various lakes results from a variety of underlying processes including the pool of species available post-glacially (a function of the time since deglaciation, distance from refugial sources, stochastic events such as catastrophic drainages and/or drainage reversals), ecological tolerances, and the vector for colonization (i.e., freshwater or marine pathways as determined by the life history of the taxon) (Tonn, 1990). Overall, species' complements of obligate freshwater fishes decline latitudinally from south to north (e.g., in Northwest Territories, fauna totals of ~40 species at 60°N, all of which are fresh water, to 31 species at 70°N at the mainland coastal margin, about 20 of which are anadromous, to 3 on the central Arctic Islands

(all of which are anadromous) to 1 anadromous species north of 76°N) (Reist, unpubl. data; Sawatzky et al., 2007). Diversity of freshwater and anadromous fish species also declines longitudinally from west to east. For example, at 60°N there are around 40 species in the Northwest Territories whereas in mainland southern Nunavut there are about 16 species (Reist, unpubl. data). Similarly, at 70°N there are 31 species in the west compared to four on the eastern extent of the mainland in Nunavut. Reduced northern and eastern complements in lakes near to marine coastal margins and connected by rivers are usually supplemented by the presence of anadromous species or the secondarily derived non-anadromous counterparts of these. Thus, for example, three species have been reported in Nettilling Lake, all of which are primarily anadromous, whereas in Lake Hazen only one species has been reported and it is a derivative of an anadromous colonizer. Forty-one fish species from 12 families are reported as occurring in the suite of lakes considered herein (excluding one introduction, rainbow trout), but including vagrant occurrences. Of these, 28 are primarily fresh water and 10 primarily anadromous. A further three species have forms (i.e., glacial races) that exhibit both tendencies. These orientations determine the likely refugial sources for the species as they colonized the areas. Distributions of individual species reflect their overall distributions (McPhail and Lindsey, 1970; Scott and Crossman, 1973;

Notes to table 2: V — vagrant Notes: 1) Primary life history — A = anadromous, F = fresh water. 2) Status — N = native, established; V = native, vagrant; I = introduced. 3) Naturally occurring species recorded to date; may be under-estimated; does not include introduced species. 4) All variant forms of Coregonus artedi complex included; shortjaw cisco, C. zenithicus, and variant forms treated separately. 5) Lake whitefish, Coregonus clupeaformis species complex includes C. nelsoni, C. clupeaformis (lake form derived from southern refugium) and C. pidschian form as anadromous type in the north. 6) Secondarily derived non-anadromous form occurs in southern waters. 7) Species is anadromous and anadromous vagrants occur in the area; form in Great Slave Lake is Kokanee, a non-anadromous derivative ARLM — Arctic lamprey FTMN — fathead minnow LKWH — lake whitefish PYWH — pygmy whitefish NNST — ninespine stickleback GOLD — goldeye PEAM — peamouth BRWH — broad whitefish ARCH — Arctic char SLSC — slimy sculpin LKCH — lake chub LNSC — longnose sucker LSCS — least cisco LKTR — lake trout SPSC — spoonhead sculpin EMSH — emerald shiner WHSC — white sucker SHCS — shortjaw cisco INCO — inconnu DPSC — deepwater sculpin SPSH — spottail shiner NRPK — northern pike CMSL — chum salmon ARGR — Arctic grayling YLPR — yellow perch FLCH — flathead chub PNSM — pond smelt CHSL — coho salmon TRPR — trout-perch WALL — walleye LNDC — longnose dace RNSM — rainbow smelt RNTR — rainbow trout BURB — burbot PRDC — pearl dace CISC — cisco SCSL — sockeye salmon BRST — brook stickleback FNDC — finescale dace ARCS — Arctic cisco RNWH — round whitefish THST — threespine stickleback



Sawatzky et al., 2007), filtered by post-glacial pathways (Crossman and McAllister, 1986; Lindsey and McPhail, 1986) and local ecological factors (Tonn, 1990). No fish species occurs in all the large lakes considered here. Lake trout (Salvelinus namaycush) exhibits the widest known occurrence (31 lakes), followed by lake whitefish (Coregonus clupeaformis) (27), Arctic grayling (Thymallus arcticus) (20), longnose sucker (Catostomus catostomus) and round whitefish (Prosopium cylindraceum) (19). Burbot (Lota lota), northern pike (Esox lucius) (17), cisco (Coregonus artedi) (16), ninespine stickleback (Pungitius pungitius) (13) and slimy sculpin (Cottus cognatus) (12) follow, then walleye (Sander vitreus) (10), white sucker (Catostomus commersonii) (9), inconnu (Stenodus leucichthys) and Arctic char (8), and lake chub (Couesius plumbeus) (7). Twenty-six species occur less frequently (i.e., 1 to 4 lakes). With one exception, threespine stickleback (Gasterosteus aculeatus) in the east, the majority of these locations are generally restricted in distribution to the southwest or western Northwest Territories. Southwestern marginal distributions include six families: lampreys (1 species), minnows (8), goldeyes (1), troutperches (1) and perches (1). Infrequent reported occurrence in large lakes does not necessarily imply low overall abundance or occurrence in the area as some species may be locally restricted by habitat preferences. Of all freshwater and anadromous fish species present in these Arctic lakes, only shortjaw cisco, Coregonus zenithicus present in Great Slave and Great Bear lakes has been evaluated as Special Concern by the Committee on the Status of Endangered Wildlife in Canada and is on schedule 2 of Canada's Species at Risk Act. Two other species of chars (bull trout, Salvelinus confluentus; Dolly Varden, Salvelinus malma malma) that occur in rivers and small lakes and thus are outside the scope of this contribution have been similarly evaluated. Generally all species within these large lakes are considered not at risk, however, strict taxonomic approaches to evaluations may not adequately address the risks to all forms of diversity (see below). In northern large and complex lakes with multiple basins and limited complements of fish species, multiple differentiated forms occur within many species. In some situations, these are exhibited as multiple life history forms (e.g., riverine vs lacustrine forms of cisco in Great Slave Lake, Blackie et al., 2012; anadromous vs resident forms of Arctic char, Reist et al., 2013) and are clearly the result of sub-specific diversification processes within the system following initial colonization. Additionally, a more complex and controversial situation appears to occur regularly, particularly in some taxonomic groups. In many situations multiple forms of closely related taxa occur (e.g., ciscoes, Coregonus spp. in Great Slave Lake — Muir et al., 2013a, 2014; lake trout, S. namaycush in Great Bear Lake, Husky Lakes and elsewhere — Chavarie et al., 2013; Kissinger et al., 2015 in this issue; Muir et al., 2015; Arctic char, S. alpinus in Lake Hazen and elsewhere — Reist et al., 1995, 2013). Two competing theories exist to explain these latter situations: 1) multiple colonizations from allopatrically derived source populations (either temporally or spatially separated, i.e., different racial refugia forms), and 2) a single colonization event followed by subsequent diversification within the lake (i.e., so-called ‘sympatric’ speciation) typically along resource-exploitation gradients. Evidence exists for both explanations to account for sub-specific variant forms (variously termed morphotypes in reference to differences in form; ecotypes in reference to ecological occurrence; ecophenotypes in reference to both form and ecological function), however, the latter appears to be most prevalent in large northern lakes. Although substantive diversity at this level appears to occur in many situations and is particularly likely in many of these lakes, the description of such variation, its formal evaluation and an effective mechanism to do so are all lacking. The resulting taxa may functionally be the equivalent of species and thus important in the integrity of the lake ecosystems, however, effective assessment, management and protection are precluded by the dearth of knowledge. Both the documentation of such within-lake sub-specific diversity and investigations of its causation are lacking for all except the most well-studied lakes. This aspect of diversification may be super-

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imposed upon the life history variation noted above, thus resulting in complex situations with multiple variant forms. Variants are often viewed as constituting distinct taxa and in many cases were originally recognized under distinct formal names (e.g., several ciscoes of the C. artedi complex in Great Slave Lake and C. zenithicus; see McPhail and Lindsey, 1970 and Scott and Crossman, 1973 for detailed taxonomic discussions). Aspects of this taxonomic morass are only now being resolved (e.g., Muir et al., 2014; Turgeon et al., 2015) and viewpoints vary regarding the level at which taxa should be recognized. Moreover, as research continues, new examples of this level of diversity are revealed, especially in large northern lakes. Two consequences result: 1) modern taxonomic nomenclature as the basis for diversity assessment significantly under-estimates the true diversity present in large northern lakes (however, older nomenclature may over-estimate taxonomic diversity) and, 2) activities (e.g., stewardship, assessment, management, research) that do not recognize this sub-specific diversity can only produce results biased in unknown ways. Recent investigations on lake nos. 9, 10, 12 and 33 indicate multiple forms of several taxa (lake trout, S. namaycush — Chavarie et al., 2013; Muir et al., 2015; Kissinger et al., 2015 in this issue; Arctic char, S. alpinus — Reist et al., 2013; ciscoes, Coregonus spp. — Muir et al., 2013a, 2013b; Howland et al., 2013; burbot, L. lota — Elmer et al., 2008). In addition to these taxa, other northern species diversify into complexes where they occur, (e.g., lake whitefish, C. clupeaformis complex; Mee et al., 2015). It is likely that still other taxa exhibit similar variability, (e.g., threespine stickleback (G. aculeatus complex), and ninespine stickleback (P. pungitius complex)), however, documentation of this phenomenon in large northern lakes is lacking. Diversity is thought to improve both the resistance of ecosystems to perturbations and their resilience for recovery by providing multiple pathways through key elements such as food webs (e.g., Awiti, 2011; Angeler et al., 2014 and references therein). Thus, in relatively depauperate large northern lakes, unrecognized and undocumented diversity may play an important role in ecosystem integrity. Unknown or unrecognized biodiversity is also at risk from anthropogenic activities. This is a fertile topic for future research on these lakes. Anthropogenic stressors Despite their northern locations and remoteness from large human population centers and perturbations focused in southern latitudes, these large Arctic lakes are susceptible to a variety of stressors, the cumulative impacts of which may be significant but are generally unknown (Table 3). The mis-perception that these systems are ‘pristine’ and subject to no, or limited, anthropogenic perturbation needs to be addressed both with respect to local stressors and widespread pervasive stressors. Lake-specific stressors' overview Urban centers Population centers for permanent settlements are present or close to nine of the lakes (Fig. 3A). In some cases, the direct or indirect effects on the lakes and their biotas may be quite substantive due to the combination of human population size and/or number of communities (e.g., for Great Slave Lake, 7 communities), but are unknown. About 28,000 people live in the Great Slave Lake sub-basin of the Mackenzie River basin, with 18,500 in Yellowknife alone (Mackenzie River Basin Board, 2004). Combined with industrial activities and other human uses, prognoses for various stressors range from unfavorable, through mixed, to good general effects. Generally, effects from urbanization are presumably buffered to some extent by the size of the lakes. Regardless, signatures of human activities are detectable over the longer term and Arctic lakes, regardless of size, appear to be fairly susceptible to direct anthropogenic influences that cumulate over time (Davydova et al., 1999; Perren et al., 2012). Most communities on the remainder of large lakes


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are small and thus likely to have very low overall impacts. Subsistence fishing, however, is likely to be locally high with unknown effects on resources (i.e., subsistence harvests are both unregulated and unrecorded in most cases). Three lakes have active mine sites near to them and many more have abandoned mines nearby. Infrastructure associated with camp development may have similar consequences to those of more permanent settlements, however, in most cases strict attention to modern environmental regulations will minimize these (e.g., in most cases development and operational criteria prohibit employees from local fishing). This is not necessarily the case with respect to past abandoned industrial sites (see below) that may be resulting in present legacy effects. Service demands imposed on lakes through urban

activities include direct activities such as recreational harvesting (low individual but potentially moderate to high cumulative effect depending on embayment, lake and/or species); domestic and/or subsistence fishery harvesting (similar consequences to above); use of recreational craft and concomitant risk of foreign or invasive species transfer, and/ or water withdrawals (if such occur). Additional indirect effects include shoreline alteration, demands for access and infrastructure on lake margins and potential for contamination through spills, and possible nutrient inputs (leading to eutrophication). Effects, however, will be scaledependent, thus local effects may be confined to local bays and/or buffered by lake size. In that context, however, synergisms with other stressors will exacerbate effects on recipient lakes and biota. Urban

Table 3 Summary of lake-specific stressors associated with large Arctic lakes. Symbols: − = unknown but possible effect, +/++/+++ = likely effect of increasing intensity. Sources include www.carc.org (accessed 24 August 2015); Stewart, 1994, 1996a,b, 1997, 1999; Stewart and Low, 2000. Name (Figure 1 Number) Northwest Territories Artillery (1) Aylmer (2) Buffalo (3) Clinton-Colden (4) Colville (5) de Gras (6) des bois (7) Faber (8) Great Bear (9) Great Slave (10) Hottah (11) Husky Lakes (Eskimo) (12) Kasba (13) la Matre (14) MacKay (15) Nonacho9 (16) Point (17) Selwyn (18) Snowbird (19) Tathlina (20) Trout (21) Wholdaia (22) Nunavut Aberdeen (23) Amadjuak (24) Angikuni (25) Baker (26) Contwoyto (27) Dubawnt (28) Ennadai (29) Ferguson (30) Garry (31) Hall (32) Hazen (33) Kamilukuak (34) Kaminak (35) MacAlpine (36) Maguse (37) Mallery (38) Napaktulik (39) Nettilling (40) Nueltin (41) Princess Mary (42) Qamanirjuaq (43) South Henik (44) Tebesjuak (45) Tehek (46) Tulemalu (47) Yathkyed (48)

Population centers on or Near

Road

Oil & gas

Active mines (on or b100 km)

Contaminated Site (on or b100 km)

All-weather

Seasonal/other

− − − − + +3 − + + +++ − + − + +8 − − − − − + −

− − + − − − − − − + − +7 − − − − − − − + − −

− − − − + + − + + − − − − + + − − − − − + −

− − − − − − − − − − − + − − − − − − − − +11 −

− + − − − ++ − − − −6 −6 − − − + − − − − − − −

− − − + − − − + − − − − − − − − − − − − − − − − − −

− − − − − − − − − − − − − − − − − − − − − − − − − −

− − − + 0 − − − − − − − − − − − − − − − − − − + − −

− − − − − − − − − − − − − − − − − − − − − − − − − −

− − − +12 − − − − − − − − − − − − − − − − − − − + − −

Fisheries1 Existing

Possible

+ + − − + − − + ++ +++ ++ + + ++ + + + − − + ++ +

+ − +C2 − + ? + + +4 +C5 +C + + + + +? + +? + +C10 + +

+ + + + +C + +C +C +C4 +C +C +C +C +C +C +C − +C − +C +C −

− + − ++ +++ ++ + + + + ++ − + − − − − − − − + + − − − −

− +? ? + − + − +C ? + − − − − −? − − +? + − − −? − − − +

− +C − − +C +C − +C +C +C − − +C − − +C − +C +C +C +C +C +C +C − −

Notes: 1. Fisheries (existing) unless otherwise noted are all subsistence fisheries. C = commercial fishery existing or quota in existence although may not have been fished recently; 2. Inconnu from system heavily fished as by-catch in Great Slave Lake fisheries. 3. Diamond mining camps (Ekati, Diavik). 4. Variable fishing harvests recommended for different locations/arms. Limits set for trophy lake trout in some arms. Residual quotas exist for some species. 5. Large multi-species commercial fisheries by areas on the lake targetting lake whitefish and lake trout. By-catch of other species may be quite high (e.g., inconnu). 6. Uranium mine in 1950s on Hottah Lake and gold mine on Great Slave Lake 7. All-weather road under construction that crosses feeder rivers and comes in close proximity to Husky Lakes. 8. Diamond mining camp (Snap Lake). 9. Hydroelectric dam placed in 1968 — effects included lake flooding. 10. Commercial walleye fishery in past — recently closed. 11. Proposed pipeline route nearby. Existing pipeline crosses upstream tributary. 12. Upstream mine.



centers require effective sewage, solid waste and hazardous goods disposals. Often this involves storage on the landscape typically in containments whose integrity depends upon both permafrost and frozen material in berms. Breaches or leakages may result in overland

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transport of noxious materials to nearby waters via runoff. Solid wastes are often burned adding noxious materials, including contaminants, to the landscapes and ultimately watersheds. Downstream flows may thus concentrate such materials in lakes. Other potential effects of

Fig. 3. Composite panel of stressors and impacts on lakes: A) Locations of communities, dams, mines, tourism lodges, roads and trails in the Northwest Territories. Map generated via the Canadian Arctic Resources Committee's (http://www.carc.org/; accessed 29 April 2015) cumulative impacts data compilation (Cizek, 2007, Peter Cizek, Cizek Environmental Services, www.cizek.ca) (yellow pins are information source reference and camera icons indicate photo available through Google Earth) and B) Locations of contaminated sites (blue dots) in the Northwest Territories and Nunavut. Data accessed from the Federal Contaminated Sites Inventory (http://www.tbs-sct.gc.ca/fcsi-rscf/opendata-eng.aspx; accessed 29 April 2015).


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urbanization include shoreline infrastructure, human activities such as recreation on the lake, water withdrawals and related activities along with potential for local contamination and spills (e.g., see Pressures on the Arctic Ecosystem from Human Activities; Resources, Wildlife and Economic Development, GNWT, accessed 31 March 2015, www.enr. gov.nt.ca). Distinct from urban centers, there exist many dozens of tourist lodges in the Northwest Territories alone (Fig. 3A). Many of the lakes included here have one or more such privately run facilities, usually operated seasonally (summer). Effects from such operations on the lakes themselves (e.g., shoreline alteration, pollution) are likely minimal (as they are not in the best interests of the lodge owners) but generally unassessed. Lodge experiences mostly focus upon trophy fishing for various species. Creel assessments conducted in the past have indicated some examples of ‘over-fishing’ and harvest levels may be specifically regulated independent of the sport-fishing regulations already in place (Stewart, 1996a,b, 1997, 1999; Stewart and Low, 2000; Muir et al., 2013b and references therein). Recent updates of angling harvests and assessments of sustainably harvestable trophy species have not been conducted for any of the lakes. Roads All-weather roads pass near to, or immediately upstream of, four of the lakes (Fig. 3A). Roads increase access to waterbodies (e.g., fishing), affect landscape drainage patterns, possibly disrupt migratory patterns of fishes, and may increase solid inputs such as silt in runoff and dust. Overall effects are likely minimal due to the few lakes and limited shoreline distances involved. Seasonal roads built during winter over tundra or boggy landscapes and/or waterbodies themselves may be quite substantive (e.g., Tibbits to Contwoyto ice road is 600 km long about 87% of which is on frozen surfaces of lakes; EBA Engineering Consultants, 2001). Ten additional lakes in this study are potentially affected by seasonal ice roads constructed annually. Those providing connections to communities (e.g., ice roads from Mackenzie trunk to Deline on Great Bear Lake or Colville Lake) likely result in little added effect on the respective lake. Those that extensively run over the lakes themselves may have somewhat larger effects, including water drawdown to enhance ice thickness and the potential for accidents or spills. Seasonal roads also alter drainages across frozen landscapes (e.g., most likely increasing flows into lakes particularly at transitions from land to ice surfaces). A second type of seasonal road includes those developed to facilitate other activities on the landscape. In this context, roads of all descriptions are a subset of linear developments that also include seismic lines, pipelines and transmission rights of way and lines (Cott et al., 2015b). These typically include winter roads to service mining activities during developmental phases (and may transition to annually developed ones as the development proceeds). Substantive linear development across the NT landscape (Fig. 3A), particularly seismic lines, although concentrated in areas distant from these large lakes may still result in downstream effects on some of the lakes. Additionally, seasonal (mostly winter) trails abound in the area particularly near to communities. Ice roads crossing streams and/or lakes may affect fish by inducing erosion at land approaches to the crossing, creating thicker ice through flooding thus delaying seasonal melt or restricting flows, entraining fish in water removals for flooding, release of harmful materials, and/or creating under-ice pressures or sounds thus displacing winter habitat use (Stewart, 2003; Martin and Cott, 2015 in this issue). Traditional land-use activities by Indigenous Peoples include food harvesting and fishing at all seasons. Established land-use patterns (e.g., snow machine trails supporting this activity) are also present in some areas (Fig. 3A). Increased access to waterbodies afforded by linear developments will often also increase exploitation of fishery resources (Kaufman et al., 2009) that, for sensitive species (e.g., lake trout), may adversely affect populations. Although less likely in northern systems, increased access also elevates the risk of introductions of aquatic invasive or non-desirable species (e.g., Kaufman et al., 2009).

All these types of access likely have overall effects on the landscape similar to each other although the effects, if any, on nearby large waterbodies are generally unknown due to limited assessment. Effects will likely be lowest for the trails category. However, there will likely be synergisms between various types of ‘road’ access and seismic lines, and between ‘roads’ and access to areas for fishers, as noted below. Oil and gas development None of the study lakes are directly influenced by oil and gas developments, however, infrastructure associated with nearby development (on upstream drainages) may affect several. An existing pipeline crosses tributaries upstream of lake no. 21 and possibly also no. 3. In addition, the Parsons Lake gas field occurs in an upland tundra area upstream of no. 12. To date no incidents affecting these lakes from this sector are known. Existing oil and gas wells are focused on the Interior Plains region of the western Northwest Territories (Fig. 3A), thus local effects on lakes in this area may be present (e.g., no. 20). Seismic activity may also affect waterbodies in this region. Concentrations of seismic lines exist near lake nos. 5, 7, 9, 12 and 21 (Fig. 3A). Potential future oil and gas development in the southern Canadian Beaufort Sea will likely involve vastly increased infrastructure in the coastal community of Tuktoyaktuk, leading to increased usage of the Tuktoyaktuk-to-Inuvik highway, i.e., similar to mining (see below) and a synergistic effect of roads as a possible increasing stressor, in this case, for no. 12. Mining Five large Arctic lakes have active mines operating in close proximity (Fig. 3A). Those in the Northwest Territories (nos. 2, 6 and 15) are near to diamond mines, however, the actual mining activity usually involves smaller nearby waterbodies. Direct effects of these activities on the larger lakes are thus most likely delivered through associated infrastructure development. One active mine for base metals in Nunavut is in close proximity to both nos. 26 and 46, likely with similar potential for effects as those noted above. The relatively few large lakes affected suggest mining has had, and will continue to have, a relatively small effect on these large Arctic lakes (but see below regarding legacy effects). Water usage and any potential tailings and their containment, however, may pose threats but these presumably are appropriately regulated through present-day stringent permitting and approvals processes. Two presently de-commissioned mines and their influences on two large lakes highlight the nature of concerns — a gold mine on no. 10 in Yellowknife operating from the 1930s to the 1990s and a uranium oxide mine operating at no. 11 in the 1950s. Residual effects from past mining activities are noticeable primarily as increased levels of heavy metals in waterbodies. For example, sediment levels of arsenic in Yellowknife Bay of Great Slave Lake have increased from ~ 100 ppm in the 1900–1925 time period to 400–500 ppm from about 1970 to 1990 (Mackenzie River Basin Board, 2004) and levels are elevated in fish collected near the mine site (Cott et al., 2015c in this issue). Numerous other mines (both de-commissioned and operating) exist in the Northwest Territories (Silke, 2009), thus overall effects may be more widespread than noted here. Legacy impacts from past mining activities may be significant. For example, an uranium and subsequently a silver mine at Port Radium on no. 9 operated from 1930 to 1982 with tailings deposited on nearby landscapes (100,000 m3 estimated) or in the lake itself (MacDonald et al., 2004). The result is significant contamination by a suite of radioactive and heavy metal elements. No comprehensive compendium exists for ongoing mining activities in various exploratory developmental phases. These are, however, relatively extensive (Fig. 3A) and several intersect with large lakes in both the Northwest Territories and Nunavut. Dams Hydroelectric facilities potentially affecting large lakes in Arctic Canada are presently restricted to the Northwest Territories.



Impoundments and water regulation affect three upstream rivers tributary to Great Slave Lake (Snare River — 140 km north of Yellowknife; Yellowknife River — 50 km north-east of Yellowknife; Taltson River — a tributary to the south side of Great Slave Lake and Nonacho Lake). Given the size of these relative to Great Slave Lake, it is unlikely they have had significant effects on the lake itself, however, local effects such as altered fish migratory patterns may have resulted. Three control structures on the Taltson River drainage constructed in 1968 have apparently affected Nonacho Lake including impoundment effects and increasing mercury loadings in predatory fish species in the system (Tam and Armstrong, 1972; Envirocon Ltd. et al., 1975). Mercury loadings in biota are a well-known consequence of impoundments associated with hydroelectric generation, thus future development may increase effects. These effects may cumulate with others affecting the immediate landscape (e.g., service roads and transmission lines). In addition to the above, other impoundments (e.g., mine tailings structures) are constructed. These represent a distinct local effect associated with that industry. Contaminated sites According to the government of Canada's definition, a contaminated site is “one at which substances occur at concentrations (1) above background (normally occurring) levels and pose or are likely to pose an immediate or long-term hazard to human health or the environment, or (2) exceeding levels specified in policies and regulations” (www.tbssct.gc.ca/fcsi-rscf/home-accueil-eng.aspx, accessed 17 March 2015). A large number of contaminated sites have been inventoried for Arctic Canada (Fig. 3B). About 29 of the 48 large lakes have contaminated sites nearby, and in some cases multiple sites exist close to the lakes or on tributaries. Some may also exist in the lakes (e.g., as the result of convenient dump sites). As for many other lake-specific stressors, these are concentrated in the Northwest Territories but by no means confined there. Sites include those associated with past industrial activity (e.g., mines, see above), military activities (e.g., de-commissioned radar sites), present community infrastructure (e.g., dumps) and a host of smaller concentrations of hazardous materials (e.g., aviation fuel drum caches). Containment of contaminants from most such sites is unknown. Given the characteristics of much of the Arctic (i.e., shallow, waterrich active layer of 1–2 m depth underlain by permafrost generally impermeable to water), concern is warranted regarding over-land seepage into nearby waterbodies thence to the large lakes. Significant overland nutrient transport occurs into waterbodies in permafrost landscapes (Vincent et al., 2013), thus accompanying fluxes of contaminants may occur. The nature and scope of this is generally unknown. Sources in this instance are local but, given their number and potential effects, pose a concern. For more pervasive stressors (e.g., climate changemediated mobilization of contaminant stores in permafrost-rich tundra environments) similar waterborne transport and subsequent bioaccumulation and bio-magnification is an issue (e.g., mercury; Stern et al., 2012). Colonizations and introductions With a single exception (rainbow trout in small lakes draining into Great Slave Lake; Sawatzky et al., 2007) there are no known intentional introductions of non-native fishes or other biota into any of the lakes considered herein. As noted above, however, accidental introduction of invasives is a risk associated with recreational watercraft use among lakes with that risk increasing with increased access (see above). No colonizations of the lakes by non-native fishes through natural processes are known to have occurred. There is evidence, however, of the occurrence of vagrant non-native species, i.e., migratory individuals that occur outside of their normal geographic distribution. To date, the evidence for this in these large lakes is restricted to coho salmon (Oncorhynchus kisutch) and sockeye salmon (Oncorhynchus nerka) in lake nos. 9 and 10, respectively (Dunmall et al., 2013). Natural dispersal

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vectors include marine coastal areas for anadromous species (including additional salmon species via the Mackenzie River basin), and the freshwater connections from southern locales via the Slave River, and upstream drainages of nos. 13, 18 and 41 in Saskatchewan and Alberta. Natural colonizations are an expected effect associated with climate change (see below, Reist et al., 2006). Pervasive stressors Long-range atmospheric transport of contaminants Long-range atmospheric transport of pollutants is a well-known pervasive stressor affecting the Arctic generally (e.g., AMAP, 1998, 2004, 2010; MacDonald et al., 2003). Prevailing winds from lower-tohigher latitudes combined with the so-called ‘grasshopper’ transport (i.e., latitudinal step-wise mobilization–deposition–re-mobilization of pollutants) result in the preferential deposition of a wide range of materials in the Arctic. These include particulates (soot, dust), long-lived organic pollutants (e.g., polychlorinated biphenyls (PCBs)), and inorganic contaminants (e.g., mercury). Deposition in the catchments and/or on surfaces of large lakes likely results in accumulation of these materials in lake sediments (Rawn et al., 2001). Those that are, or become, bioactive may also enter food webs and ultimately bio-magnify. Accumulation of such materials in large lakes may be aided by key idiosyncratic landscape attributes of the Arctic, such as permafrost, and the typically large drainage basins. Similarly, a synergistic linkage between altered drainage patterns, climate change and local human activities (e.g., roads, trails, seismic lines; local contaminant sources) likely aids transport, however, the scale and significance of this is unknown. In most cases, simple deposition and sequestration in lake sediments is unlikely to represent any follow-on issues. Issues come to the fore when re-mobilization of sequestered contaminants and their entry into ecological systems occurs (e.g., through flooding associated with lake impoundments). Periodic assessment and monitoring of levels for key contaminants occur in the larger lakes (e.g., Great Bear Lake; MacDonald et al., 2004). Additionally, routine monitoring of some contaminants occurs in the biota, especially higher trophic-level predators, present in the lakes (e.g., Evans et al., 2005). Most lakes or their biota, however, are not routinely monitored, thus accurate understanding of the scale of this problem is not presently possible. Climate variability and change Much has been written regarding the effects of climate change on waterbodies in the Arctic (e.g., Rouse et al., 1997; Schindler, 2009; Wrona et al., 2013; Vincent et al., 2013). Generalities include direct effects such as shifts in nature and timing of key events in the hydrological cycle (e.g., rain vs. snow, duration of ice-on/ice-off seasons, warming and deepening of the epilimnion, increased anoxia at depths). A wide range of indirect effects are also forecast, ranging from increased nutrient loadings and associated productivity shifts to altered biodiversity at all levels of the ecosystem. A suite of potential third-order effects also exist including permafrost shifts and drying landscapes, increasing terrestrial fire with cascading effects on waterbodies such as benthic invertebrate biomass (Scrimgeour et al., 2000) and fish year-class strengths (Cott et al., 2010). Most empirical studies have been conducted on smaller waterbodies given the relative logistic difficulties presented by large lakes (see below). Climate change and its cascading effects will undoubtedly alter most, if not all, large Arctic lakes. Detailed effects will depend in part upon the existing circumstances (e.g., location, elevation, ecozone and associated surficial geology, connectivity and biotic assemblages). Lake size will also play a significant role in scaling the possible effects or altering the timing of the effects. Presumably lakes with larger volumes will be both resistant and resilient to many effects of climate change. Surface area, however, will mediate the responses (i.e., larger surface:volume ratios will alter direct energy uptake, as will seasonal ice dynamics). Similarly, complexity of the lake basin will likely alter effects with


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small embayments on morphologically complex lakes being affected sooner and to a greater degree. In general, the effects of climate variability and change will be more pronounced and occur sooner for smaller to medium-sized large lakes at or near key environmental transitions. Those immediately north of the present-day tree line, for example, will likely experience significant effects from increased terrestrial production and the shift from tundra to a treed biome, and related hydrological changes. Similarly, lakes with substantive areas of permafrost landscapes in their drainage basins will likely see earlier and more substantive changes. Generally these will likely be towards increasing eutrophication thus mimic direct local effects of many human activities that add nutrients. Nearshore areas and embayments of the larger lakes will likely be the first to experience effects, however, over the longer term considerable lake-wide effects will accrue (e.g., see Davydova et al., 1999 synopsis for Lake Ladoga, a large Russian lake). The current absence of baseline information and ongoing monitoring programs will preclude future documentation of effects for these lakes. Moreover, distinguishing causation of changes (e.g., climate change vs local anthropogenic stressor) will be problematic. Cumulative impacts The local (point-source) and the pervasive stressors noted above will cumulate in various ways and to varying degrees to result in cumulative impacts on these large Arctic lakes (e.g., see Schindler, 2001). In many cases these effects will be additive (e.g., increased nutrient loadings combining with warmer water regimes to facilitate greater production). In other cases the effects will be synergistic (i.e., multiplicative thus producing far greater than expected changes from additive events) and may result in substantive alteration of the ecosystems and the provision of services to humans (e.g., climate change exacerbating legacy contaminant releases combined with ongoing contaminant loadings and faster cycling in biota in warmer environments). In virtually all cases, the outcomes will generally be unpredictable both with respect to the consequences for a particular lake and in terms of the nature of those consequences. Combined with the paucity of existing knowledge and the absence of ongoing programs to assess and monitor most of the lakes, the changes and/or losses will occur both in the absence of knowledge of reference conditions and also without effective documentation. Large lakes are effective sentinels and integrators of changes in their watersheds (Adrian et al., 2009; Schindler, 2009) particularly in the Arctic (Vincent et al., 2013), however, despite repeated expressions of concern, little has changed in the past 15 years with respect to the large Arctic lakes – “Research on northern great lakes: a national disgrace” (Schindler, 2001, p 25) – is still a truism for these large Arctic lakes. It is time to reverse this status quo and develop comprehensive and effective research and monitoring regimes from which effective management actions may result. Repeating the legacy and costly attempts at recovery being undertaken for the Laurentian Great Lakes with respect to the large Arctic lakes is an inappropriate option. Protection, management, concerns and recommendations Freshwater areas generally do not receive explicit protection unless they are encompassed within a terrestrial area that itself is protected. Accordingly, Husky Lakes is currently protected from development under Section 8.4 of the Inuvialuit Final Agreement. Other land claims in the Northwest Territories, either settled or under negotiation, provide interim protection, or will do so, to lands adjacent to a number of other large Arctic lakes and/or the lakes themselves in some fashion (e.g., nos. 1, 5, 7, 11, 20 and 21). This includes interim land withdrawals to ultimately establish a national park on the east arm of Great Slave Lake (http://www.nwtpas.ca/maps/map2_established_interim_and_ proposed_protection.pdf accessed, 7 April 2015). In Nunavut, two lakes (nos. 26 and 33) are encompassed within national parks or park

reserves. Only one lake considered herein is within any sort of other protected area in the Arctic (i.e., no. 36 in the Queen Maud Migratory Bird Sanctuary) that does not offer protection to the lake itself. In the context of the above, however, the existence of a settled land claim and associated designation of traditionally used lands (often referred to as ‘private lands’) may offer additional protection to some lakes. Lakes per se are not managed in the Arctic. Rather, aspects of management fall to various government departments that may include a mixture of federal, territorial and land claim entities (if the area is within a settled claim). For example, sport fisheries are managed by the territorial governments, subsistence food fisheries are generally managed by local resource committees (if under settled land claims) or remain unmanaged (if outside a land claim area), and commercial fisheries are managed under license by Fisheries and Oceans Canada. Given their size and complexity, commercial fisheries on Great Slave Lake are managed by an advisory committee that includes members from First Nations, government and industry (commercial and sport fisheries, lodge operators) representatives that report to Fisheries and Oceans Canada. Commercial fisheries on other large Arctic lakes are managed through a licensing process with harvest reporting being a requirement for targeted species, but not for by-catch species. Similarly, water stewardship and monitoring is a complex mixture involving regulatory boards, and territorial and federal government departments. Industrial development activities generally have a similar complex regulatory framework that may differ depending upon the industry, the territory and/or the area within a territory. Given the above circumstances, it is difficult to envision a situation where comprehensive and collective management of all activities that may affect the large Arctic lakes is, in fact, effective. Management shortcomings are exacerbated by the knowledge issues discussed above, inadequate approaches in some cases (e.g., no mechanism to evaluate and protect sub-specific diversity), and are further affected simply by the size of the waterbodies themselves. Moreover, in a paper regarding time taken for environmental reviews across Canada, de Kerckhove et al. (2013, p 520) note that “…. Canada's federal Commissioner of the Environment and Sustainable Development reported that resource development is currently outpacing improvements to environmental protection, and this, in tandem with the recent changes to environmental laws such as the Fisheries Act, is putting the public and wild resources at risk (Office of the Auditor General of Canada, 2012)”. Accordingly, a distinct gap exists in management of individual and cumulative activities that likely affect these lakes. In the face of a rapidly and substantively changing Arctic, this gap should be re-dressed as soon and as effectively as possible. Conclusions Given their remoteness relative to the populated southern third of Canada, most Canadians either have little awareness of the large Arctic lakes or perceive them to be relatively pristine and little affected by human activities. As we have shown, this perspective is untrue. Despite their remoteness and size, most are likely influenced, albeit to varying degrees, by anthropogenic stressors, many more heavily than others. Overall there is a dearth of knowledge regarding these lakes, yet there is a wide range of stressors that present imminent threats to the lakes. Re-dress of these knowledge gaps for the large lakes is urgently required. Moreover, despite the focus here on the large lakes of the Canadian Arctic, it should be noted that these are embedded within a much broader landscape that itself is covered by water (i.e., 18% of the water surface area of Canada occurs in the Arctic). Most Arctic lentic systems are much smaller than those examined here, however, collectively they cover significant percentages of the area of the Arctic not only in Canada, but globally as well (Vincent et al., 2013). Some estimates suggest that greater than 61,000 lakes with a surface area N0.1 km2 exist in the global Arctic comprising a combined surface area of N 200,000 km2 (Grosse et al., 2011 as cited in Vincent et al., 2013). Issues outlined



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