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Fourhorn sculpin (Myoxocephalus quadricornis) is ubiquitous in Canadian Arctic waters with a more common marine and brackish form and a rarer freshwater form. There is a paucity of information available for the freshwater form from Canadian waters. In the summer of 2003, we serendipitously collected 28 of the freshwater form of fourhorn sculpin from Lake Tuborg, Ellesmere Island, Nunavut. The fish ranged in size from 62 mm to 171 mm total length and age from 1 to 12 years with females growing faster and to a larger theoretical maximum total length than males. The sculpin preyed mainly upon the crustacean, Mysis segerstralei, but were also opportunistic feeders (e.g., Arctic charr (Salvelinus alpinus) eggs) and cannibalistic. Although our sample of fourhorn sculpin is small, the data from these fish represent the only information from a fully freshwater form population of the species from Canadian waters. We also present an updated list of the known Canadian lacustrine and riverine populations of fourhorn sculpin. [ABSTRACT FROM AUTHOR]

Determination of unit-stock structure and the assignment of individuals from mixed groups to stock-of-origin is important to conservation and management of Arctic riverine fishes. Northern form Dolly Varden Char ( Salvelinus malma malma ) are closely linked to perennial groundwater sources during the freshwater stages of their life cycle. This close connectivity provides an ideal circumstance for stock discrimination using archived sagittal otoliths (1986–2007) collected from the river drainages of the study area (Firth River, Yukon Territory (YT), Babbage River, YT, Big Fish River, Northwest Territories (NT), Rat River, NT, and Vittrekwa River, NT). Laser ablation-ICP–MS techniques were employed to measure 87 Sr/ 86 Sr isotopes and trace elements (Sr, Ba, S, Zn, Mg, P) from dorso-ventral otolith thin sections. Random forest model, learning algorithm and tree classification provided 94.4% classification success for individual fish to the river systems (putative stocks). Misclassifications within the model occurred among the Vittrekwa, Babbage, and Rat river drainages. Strontium, 87 Sr/ 86 Sr ratio and Ba were the most significant discriminators within the model, although removal of the remaining elements reduced overall discriminatory power. Microchemical analyses of archived otoliths provided high classification and discrimination success thus can be used as a tool for fisheries managers in developing effective management and conservation plans regarding mixed-stock fisheries for this species. [ABSTRACT FROM AUTHOR]

A discriminant function analysis model based on carbon and nitrogen stable isotope values was used to identify offspring of piscivorous large-form and non-piscivorous small-form Arctic charr, Salvelinus alpinus, morphotypes from Lake Hazen, Nunavut, Canada., The ability to distinguish between morphotypes in Lake Hazen was based mainly on the separation of δ15N signatures because of adult occupation of significantly different trophic levels. A smaller difference between adult morphotype δ13C values, most likely combined with a potential increase in variation among individuals at the egg stage, a faster turnover rate in carbon relative to nitrogen and the size at which fish can be sampled in the open-water season in Lake Hazen, probably contributes to the limited use of δ13C in distinguishing between morphotype offspring., Based on young-of-the-year (YOY) origin estimates, the adult morphotypes were estimated to contribute approximately equally to the YOY population; however, the morphotype offspring were differentially distributed among sampled nursery sites., Unequal distribution corresponds with prerequisites suggested for the evolution of trophic specialists within a single population that experiences assortative mating based on trophic specialisation. Differential use of spawning areas and the more or less equal importance of both Lake Hazen forms found in this study, taken alongside previously noted morphological variation and available genetic evidence, suggest that Lake Hazen may be an example of early divergence relative to other Arctic charr populations described in the literature. [ABSTRACT FROM AUTHOR]

Abstract: A snapshot sample of Arctic charr (Salvelinus alpinus) from Heintzelman Lake (81°42′N, 66°56′W), Ellesmere Island, Canada was used to elucidate the biological and life-history factors potentially influencing individual total mercury (THg) concentrations. Migratory history was significant, with anadromous fish having a lower mean THg concentration (64μg/kg ww) than the non-anadromous Arctic charr (117μg/kg ww). The increase in individual THg concentration with age was shown to be independent of length-at-age when large and small individuals within the same age groups were compared. Similarly, the diets of individual Arctic charr were comparable regardless of size, and there was no apparent ontogenetic shift in diet that could explain differences in length-at-age or THg concentration among fast- and slow-growing groups of fish (i.e., fish of the same age but differing sizes). Maturity state was also not related to THg concentration, but appears to be related to differences in length-at-age, with slow-growing fish allocating more energy to reproduction than fast-growing conspecifics. The differences in THg concentration among individual Arctic charr were best explained by fish age. We suggest that the increase in mercury concentration with age can be altered by a shift in diet (e.g., to piscivory) or habitat (e.g., anadromy), but is otherwise unaffected by changes in size or length-at-age. [Copyright &y& Elsevier]

Dyck and Kebreab (2009) analyzed the required summer intake of arctic char, ringed seal blubber, and berries that polar bears must consume to maintain their body mass during a summer ice-free period. Their calculations of required intake were based on the amount of body mass lost by fasting bears in western Hudson Bay. However, fasting polar bears are in a low metabolic state with energetic requirements less than those of an active, feeding bear. Estimates of energy consumed by captive brown bears were 4-4.5 times higher than the estimates used by Dyck and Kebreab for similar diets. Furthermore, the authors' portrayal of the availability of these resources is misleading because they do not acknowledge limited accessibility of arctic char due to their limited anadromy and predominant occurrence in streams too deep to facilitate efficient capture by polar bears; effects of large interannual fluctuations in the availability of berries or competition with other frugivores; high energetic requirements associated with lengthy foraging times required to locate and consume sufficient fruit; and data from southern Hudson Bay, western Hudson Bay, and the southern Beaufort Sea that document continued declines in several biological indices over the past several decades despite the authors' suggested availability of terrestrially based food resources. Based on current information, arctic char, berries, and ringed seals in open water do not appear to be food sources with the potential to offset the nutritional consequences of an extended ice-free period. [ABSTRACT FROM AUTHOR]

Arctic freshwater and diadromous fish species will respond to the various effects of climate change in many ways. For wide-ranging species, many of which are key components of northern aquatic ecosystems and fisheries, there is a large range of possible responses due to inter-and intra-specific variation, differences in the effects of climate drivers within ACIA regions, and differences in drivers among regions. All this diversity, coupled with limited understanding of fish responses to climate parameters generally, permits enumeration only of a range of possible responses which are developed here for selected important fishes. Accordingly, in-depth examination is required of possible effects within species within ACIA regions, as well as comparative studies across regions. Two particularly important species (Arctic char and Atlantic salmon) are examined as case studies to provide background for such studies. [ABSTRACT FROM AUTHOR]

Fisheries for arctic freshwater and diadromous fish species contribute significantly to northern economies. Climate change, and to a lesser extent increased ultraviolet radiation, effects in freshwaters will have profound effects on fisheries from three perspectives: quantity of fish available, quality of fish available, and success of the fishers. Accordingly, substantive adaptation will very likely be required to conduct fisheries sustainably in the future as these effects take hold. A shift to flexible and rapidly responsive 'adaptive management' of commercial fisheries will be necessary; local land-and resource-use patterns for subsistence fisheries will change; and, the nature, management and place for many recreational fisheries will change. Overall, given the complexity and uncertainty associated with climate change and related effects on arctic freshwaters and their biota, a much more conservative approach to all aspects of fishery management will be required to ensure ecosystems and key fished species retain sufficient resiliency and capacity to meet future changes. [ABSTRACT FROM AUTHOR]

Projected shifts in climate forcing variables such as temperature and precipitation are of great relevance to arctic freshwater ecosystems and biota. These will result in many direct and indirect effects upon the ecosystems and fish present therein. Shifts projected for fish populations will range from positive to negative in overall effect, differ among species and also among populations within species depending upon their biology and tolerances, and will be integrated by the fish within their local aquascapes. This results in a wide range of future possibilities for arctic freshwater and diadromous fishes. Owing to a dearth of basic knowledge regarding fish biology and habitat interactions in the north, complicated by scaling issues and uncertainty in future climate projections, only qualitative scenarios can be developed in most cases. This limits preparedness to meet challenges of climate change in the Arctic with respect to fish and fisheries. [ABSTRACT FROM AUTHOR]

Abstract: The amount of genetic variation in aquaculture strains of North American Arctic charr (Salvelinus alpinus) originating from the Fraser River (Labrador), Nauyuk Lake and Tree River (Nunavut), and Lake Aleknagik (Alaska) was compared to that in natural populations using six microsatellite markers. Aquaculture strains originating from Nauyuk Lake and Tree River had less genetic variability than their wild source populations in terms of allelic diversity, but not necessarily in observed heterozygosity. In aquaculture strains, the average number of alleles is positively associated with the number of fish used to produce each strain. Pairwise tests for genetic differentiation between populations were significant for all but three comparisons. These comparisons consisted of consecutive year classes of cultured Labrador and Nauyuk fish originating from the same wild collections. A neighbour joining tree grouped samples according to their geographic origin. These results indicate that hatchery strains and natural populations of Arctic charr are genetically differentiated and that small founding population sizes have contributed to reduced genetic variation in aquaculture strains. This genetic survey is intended as a baseline for future genetic monitoring of Arctic charr aquaculture strains and will aid in the development of breeding programs for production and management. [Copyright &y& Elsevier]

Reports on the presence of bull trout from four locations in the Sahtu Settlement Area of the Northwest Territories. Geographical range of the bull trout; Tendency for the bull trout to be distributed in high-gradient streams and rivers of the south-central Mackenzie River valley.

Stable isotope ratios of nitrogen (δ 15 N) of benthic primary consumers are often significantly related to water depth. This relationship is commonly attributed to preferential uptake of 14 N from sinking particulate organic matter (POM) by microbes, and suggests that relationships between δ 15 N and water depth may be affected by local POM sources and flux dynamics. We examined the relationships between δ 15 N and water depth (20–500 m) for six trophic functional groups using a mixed effects modelling approach, and compared relationships between two contiguous Arctic marine ecosystems with different POM sources and sinking export dynamics: the Canadian Beaufort Sea and Amundsen Gulf. We demonstrate for the first time in the Arctic that δ 15 N values of mobile epifaunal carnivores increased as a function of depth when considered separately from benthopelagic and infaunal carnivores, which contrarily did not exhibit increasing δ 15 N with depth. The δ 15 N of suspension/filter feeders, infaunal deposit feeders and bulk sediment also increased with water depth, and the slopes of the relationships were steeper in the Amundsen Gulf than in the Beaufort Sea. We propose that regional differences in slopes reflect differences in POM sources exported to the benthos. In the Beaufort Sea, terrestrial POM discharged from the Mackenzie River quantitatively dominates the sedimentary organic matter across the continental shelf and slope, dampening change in δ 15 N of benthic POM with depth. In the Amundsen Gulf, we attribute a faster rate of change in δ 15 N of POM with increasing depth to larger contributions of marine-derived POM to the benthic sedimentary pool, which had likely undergone extensive biological transformation in the productive offshore pelagic zone. Differences in POM input regimes among regions should be considered when comparing food webs using stable isotopes, as such differences may impact the rate at which consumer δ 15 N changes with depth. [ABSTRACT FROM AUTHOR]

Eight sexually mature sockeye (Oncorhynchus nerka) and one sexually mature pink salmon (O. gorbuscha) were captured in the subsistence fishery in the Sachs River estuary at Sachs Harbour, Banks Island, Northwest Territories (NT) in August 1993. We also report a first record for coho salmon (O. kisutch) in Great Bear Lake, NT. These capture locations are well outside the known distributions for the species. A pink salmon captured in the West Charnel, Mackenzie River near Aklavik, NT, and a chum salmon (O. keta) from Cache Creek, NT, also represent new capture locations within the distribution of the species. [ABSTRACT FROM AUTHOR]

Aims We investigated post-glacial recolonization of the North American Arctic by Arctic char ( Salvelinus alpinus) and examined potential hybridization between different glacial lineages upon secondary contact. Location North American Arctic and adjacent areas. Methods We collected mt DNA sequence data from 1355 individuals from 110 sampling locations and data from nine microsatellite loci from 931 individuals from 37 locations. We assessed the phylogenetic relationships and geographical distribution of mt DNA haplotypes and conducted historical demographic analyses. We used a Bayesian clustering analysis method to detect potential hybridization between glacial lineages. Results Two highly divergent mt DNA lineages were identified in the Arctic region with distinct but overlapping geographic distributions: one in Beringia and the other over the entire Arctic Archipelago and coastal mainland east of Alaska. The microsatellite data also implied the existence of these two lineages. Evidence of hybridization was detected between the Arctic lineage and an Atlantic lineage in eastern North America. Main conclusions Our data suggested survival and recolonization from two northern glacial refugia: one in Beringia and another in a smaller refugium, perhaps in the Arctic Archipelago itself or a separate refugium within Beringia. Patterns of hybridization detected supported the presence of a secondary contact zone between glacial lineages in the eastern Canadian Arctic. [ABSTRACT FROM AUTHOR]

Countergradient variation ( CGV) is defined as genetic variation that counteracts the negative influences of the physical environment, minimising phenotypic variability along an environmental gradient. CGV is thought to have relevance in predicting the response of organisms to climate variability and change. To test the hypothesis that growth rate increased with latitude, consistent with CGV, young-of-the-year ( YOY) Arctic charr, Salvelinus alpinus, were examined along a ~27° latitudinal gradient in central and eastern Canada. Growth rates were estimated from fork lengths standardised by the thermal opportunity for growth based on experienced water temperatures derived using otolith oxygen stable isotopes. Results demonstrated patterns consistent with CGV, where northern populations demonstrated faster growth rates. A secondary aim was to test for similar geographical patterns in otolith-inferred metabolic rates, which reflect the energetic costs of standard metabolic rate ( SMR) and other processes such as feeding, locomotion, thermoregulation, reproduction and growth. Results demonstrated a significant, positive relationship between otolith-inferred metabolic rate and latitude, which may reflect an increase in one, or a combination, of the above-noted physiological processes. The similar latitudinal pattern in growth and otolith-inferred metabolic rates suggests greater intake of food per unit of time by northern fish. The phenotypic variation in physiological traits observed here demonstrates the significant adaptability of Arctic charr to different thermal regimes with different growing season lengths. Determining the relative contributions of phenotypic plasticity and genetic variation to the observed latitudinal variation will be critical to predicting the responses of Arctic charr to climate change more accurately. [ABSTRACT FROM AUTHOR]

Abstract: Distribution and diet of bottom-dwelling Arctic cod were studied in the nearshore Canadian Beaufort Sea in summer of 2006–2009 using a 3m benthic beam trawl. In total, 82 stations were visited ranging in depth from 8 to 128m. Fish densities were generally low for benthic habitats; pelagic fish occurrence was not assessed. We observed a gradual increase in both the biomass of daily food rations and their energetic content over fish age. Overall, fish were able to obtain high food rations indicating that the Beaufort Sea Shelf has sufficient food resources for them. Demersal Arctic cod fed mainly on copepods (Pseudocalanus spp., Calanus glacialis, Calanus hyperboreus, Limnocalanus macrurus and Jaschnovia tolli), amphipods (Apherusa glacialis and Themisto libellula) and mysids (Mysis oculata). Further studies, particularly focused on combined pelagic/benthic sampling, are needed to fully assess ecology of the Arctic cod population in the Canadian Beaufort Sea. [Copyright &y& Elsevier]

Temporal diet changes can be detected by comparing δ13C and δ15N values between tissues with different isotopic turnover times. However, other factors contribute to disparities in δ13C and δ15N signatures between tissues and could confound the interpretation of stable isotope data. We examined the effects of ecological factors on differences in muscle and liver δ13C and δ15N signatures of Arctic charr [ Salvelinus alpinus, (L.)] to determine whether their effects were large enough to influence studies of diet change. In addition, we examined whether differences in lipid content accounted for a significant portion of the differences in δ13C values between tissues. Results indicated that life history, diet, reproductive status and gender had significant effects on the differences in δ13C values between tissues, while gender and diet significantly affected differences in δ15N values. Differences in % lipid content between tissues also explained approximately 74% of the observed variation in the difference in δ13C values between tissues. The differences in δ13C values observed between muscle and liver tissues may be partially explained by physiological differences in lipid storage and use between tissues associated with ecological factor effects. These results demonstrate that ecological factors other than a change in diet can influence the differences in δ13C and δ15N signatures between muscle and liver tissues. However, the impact of ecological factors on studies of diet change depends on how the magnitude of the factor effects compared with a biologically meaningful change in diet. [ABSTRACT FROM AUTHOR]

Streams were surveyed along the Mackenzie Valley, Northwest Territories, to investigate the distribution and biology of riverine char. Bull trout (Salvelinus confluentus) were captured in 24 of 43 streams sampled from three watersheds: the Kotaneelee River, the South Nahanni River, and the Central Mackenzie Mountains. The first confirmed sympatric bull trout and Dolly Varden (Salvelinus malma) populations in the Northwest Territories are reported from the Gayna River (~65°17' N, 129°21' W). This location represents a geographical range extension for bull trout approximately 200 km northwest of the previous northernmost published location in the central Northwest Territories (~64°30' N and 125°00' W, Great Bear River). It also extends the geographical range of Dolly Varden south approximately 300 km from the closest known populations located in the Peel River basin. The identification of this geographic range expansion is a result of extending both our sampling range and our ability to identify riverine chars accurately. In bull trout, we observed two different growth patterns, which correspond to non-migratory and migratory life histories. Northern bull trout populations are relatively small and widespread, and they are separated from one another by large distances and in some cases by natural barriers. Although these populations share similar biological traits with their southern counterparts, the northern fish mature later and do not spawn as often, which increases their sensitivity to exploitation and other anthropogenic perturbations. [ABSTRACT FROM AUTHOR]

The importance of marine prey sources for partially anadromous fishes has received little study and is complicated by considerable plasticity in life history. We determined proportional contributions of marine, freshwater benthic, and freshwater pelagic prey to anadromous and resident Arctic char ( Salvelinus alpinus) and lake trout ( Salvelinus namaycush) from several partially anadromous populations in the Canadian Arctic. Bayesian mixing models (MixSIR) applied to δ34S and δ13C ratios in lake-specific models indicated that marine prey accounted for 90%-91% of anadromous Arctic char diet and 60%-66% of anadromous lake trout diet. When these estimates were combined with proportion of anadromous individuals in partially anadromous populations, marine food sources accounted for 31%-44% of Arctic char population productivity and 16%-26% of lake trout population productivity. Although future research is needed to refine and quantify variability around these estimates, our results will allow better predictions of the effects of anthropogenic stressors on partially anadromous fishes. [ABSTRACT FROM AUTHOR]

Climate change is projected to cause significant alterations to aquatic biogeochemical processes, (including carbon dynamics), aquatic food web structure, dynamics and biodiversity, primary and secondary production; and, affect the range, distribution and habitat quality/quantity of aquatic mammals and waterfowl. Projected enhanced permafrost thawing is very likely to increase nutrient, sediment, and carbon Ioadings to aquatic systems, resulting in both positive and negative effects on freshwater chemistry. Nutrient and carbon enrichment will enhance nutrient cycling and productivity, and alter the generation and consumption of carbon-based trace gases. Consequently, the status of aquatic ecosystems as carbon sinks or sources is very likely to change. Climate change will also very likely affect the biodiversity of freshwater ecosystems across most of the Arctic. The magnitude, extent, and duration of the impacts and responses will be system-and location-dependent. Projected effects on aquatic mammals and waterfowl include altered migration routes and timing; a possible increase in the incidence of mortality and decreased growth and productivity from disease and/or parasites; and, probable changes in habitat suitability and timing of availability. [ABSTRACT FROM AUTHOR]

The article presents findings and recommendations from Arctic ecosystem scientists regarding the impacts of climate changes. They argue that changes in runoff, water levels, and riverine regimes will probable result in more pluvial systems. They predict decreases in summer water levels of lakes and rivers and permafrost thawing resulting in greater nutrient and sediment loads in aquatic systems detrimental to benthic fauna. Changes in ice cover are expected to increase UV radiation and alter circulation patterns. Changes in biodiversity of freshwater systems are very likely to occur. Contaminants will probably increase and diseases will likely spread. They recommend additional funding for research and educational programs.

Climate change is likely to act as a multiple stressor, leading to cumulative and/or synergistic impacts on aquatic systems. Projected increases in temperature and corresponding alterations in precipitation regimes will enhance contaminant influxes to aquatic systems, and independently increase the susceptibility of aquatic organisms to contaminant exposure and effects. The consequences for the biota will in most cases be additive (cumulative) and multiplicative (synergistic). The overall result will be higher contaminant loads and biomagnification in aquatic ecosystems. Changes in stratospheric ozone and corresponding ultraviolet radiation regimes are also expected to produce cumulative and/or synergistic effects on aquatic ecosystem structure and function. Reduced ice cover is likely to have a much greater effect on underwater UV radiation exposure than the projected levels of stratospheric ozone depletion. A major increase in UV radiation levels will cause enhanced damage to organisms (biomolecular, cellular, and physiological damage, and alterations in species composition). Allocations of energy and resources by aquatic biota to UV radiation protection will increase, probably decreasing trophic-level productivity. Elemental fluxes will increase via photochemical pathways. [ABSTRACT FROM AUTHOR]

In general, the arctic freshwater-terrestrial system will warm more rapidly than the global average, particularly during the autumn and winter season. The decline or loss of many cryospheric components and a shift from a nival to an increasingly pluvial system will produce numerous physical effects on freshwater ecosystems. Of particular note will be reductions in the dominance of the spring freshet and changes in the intensity of river-ice breakup. Increased evaporation/evapotranspiration due to longer ice-free seasons, higher air/water temperatures and greater transpiring vegetation along with increase infiltration because of permafrost thaw will decrease surface water levels and coverage. Loss of ice and permafrost, increased water temperatures and vegetation shifts will alter water chemistry, the general result being an increase in Iotic and lentic productivity. Changes in ice and water flow/levels will lead to regime-specific increases and decreases in habitat availability/quality across the circumpolar Arctic. [ABSTRACT FROM AUTHOR]

Changes in climate and ultraviolet radiation levels in the Arctic will have far-reaching impacts, affecting aquatic species at various trophic levels, the physical and chemical environment that makes up their habitat, and the processes that act on and within freshwater ecosystems. Interactions of climatic variables, such as temperature and precipitation, with freshwater ecosystems are highly complex and can propagate through the ecosystem in ways that are difficult to project. This is partly due to a poor understanding of arctic freshwater systems and their basic interrelationships with climate and other environmental variables, and partly due to a paucity of long-term freshwater monitoring sites and integrated hydro-ecological research programs in the Arctic. The papers in this special issue are an abstraction of the analyses performed by 25 international experts and their associated networks on Arctic freshwater hydrology and related aquatic ecosystems that was initially published by the Arctic Climate Impact Assessment (ACIA) in 2005 as "Chapter 8- Freshwater Ecosystems and Fisheries". The papers provide a broad overview of the general hydrological and ecological features of the various freshwater ecosystems in the Arctic, including descriptions of each ACIA region, followed by a review of historical changes in freshwater systems during the Holocene. This is followed by an assessment of the effects of climate change on broad-scale hydro-ecology; aquatic biota and ecosystem structure and function; and arctic fish and fisheries. Potential synergistic and cumulative effects are also discussed, as are the roles of ultraviolet radiation and contaminants. The nature and complexity of many of the effects are illustrated using case studies from around the circumpolar north, together with a discussion of important threshold responses (i. E. , those that produce stepwise and/or nonlinear effects). The issue concludes with summary the key findings, a list of gaps in scientific understanding, and policy-related recommendations. [ABSTRACT FROM AUTHOR]

Various types of ecosystem-based climate proxies have been used to assess past arctic change. Although Iotic records are relatively poor because of the constant reworking of riverine material, high-quality lentic data have been assembled back to the end of the Pleistocene and deglaciation of the circumpolar Arctic. In general, climatic variations in the Holocene, partly due to changes in the shrinking effect of glacier coverage, produced significant temporal and spatial variations in arctic hydrology and freshwater ecosystems. Of particular note were the vast expansions of northern peatlands during major protracted periods of wetting. More recent lake biota and sedimentiological data reflect the general warming trend that has occurred over the last one to two centuries and indicate major changes to freshwater characteristics such as ice-cover duration and thermal stratification. Such data provide an excellent baseline against which future effects of climate change can be both projected and measured. [ABSTRACT FROM AUTHOR]

Large variations exist in the size, abundance and biota of the two principal categories of freshwater ecosystems, Iotic (flowing water; e. G. , rivers, streams, deltas and estuaries) and lentic (standing water; lakes, ponds and wetlands) found across the circumpolar Arctic. Arctic climate, many components of which exhibit strong variations along latitudinal gradients, directly affects a range of physical, chemical and biological processes in these aquatic systems. Furthermore, arctic climate creates additional indirect ecological effects through the control of terrestrial hydrologic systems and processes, particularly those associated with cryospheric components such as permafrost, freshwater ice and snow accumulation/ablation. The ecological structure and function of arctic freshwater systems are also controlled by external processes and conditions, particularly those in the headwaters of the major arctic rivers and in the adjacent marine environment. The movement of physical, chemical and biotic components through the interlinked lentic and Iotic freshwater systems are major determinants of arctic freshwater ecology. [ABSTRACT FROM AUTHOR]

Presents a study which looked at short interspersed repetitive elements (SINE), which have been found in genus Salvelinus. Definition of a retroposon; Information on SINE; Method used for the study; Results of the study.

Northern form Dolly Varden is an anadromous char with significant ecological value found in high-gradient rivers of the Western Arctic. Because of declines in population abundance, Dolly Varden was recently designated as "Special Concern" under the federal Species at Risk Act. This species is also of great cultural and dietary significance to Indigenous Peoples of many communities in the Western Arctic; thus, expanding knowledge of the distribution, biology, and essential habitat is an important priority. We present results of a fisheries survey in the headwaters of the Arctic Red River, Northwest Territories, that focused on confirming the presence of Dolly Varden. Of 143 fish captured among 12 sampling locations, two were Arctic grayling (Thymallus arcticus), 33 were slimy sculpin (Cottus cognatus), and 108 were char identified using qualitative and quantitative morphological features. A subsample of 44 char voucher specimens were frozen whole and later identified using a linear discriminant function (LDF) based on meristic counts and morphological measurements, and a mitochondrial DNA genetic marker. LDF scores indicated that char collected in the Arctic Red River were northern form Dolly Varden. Genetic analysis showed that all but one char possessed mitochondrial DNA sequences common in northern form Dolly Varden from Canada. Our results confirm the presence of Dolly Varden in the Arctic Red River headwaters, extending the confirmed known distribution of this taxon in the Northwest Territories approximately 450 km south and 100 km east of previously delimited areas. [ABSTRACT FROM AUTHOR]

Scanning proton microprobe analysis was used to determine the distribution of strontium (Sr) in otoliths from arctic charr (Salvelinus alpinus) of known non-anadromous, known anadromous, and unknown life histories. Strontium concentration patterns in otoliths of known non-anadromous charr were low and relatively flat (with little variation) from the core area to the outermost edge of the otolith, while patterns for known anadromous chart were characterized by a similar low, flat region for the first several years of life, followed by marked oscillatory increases and decreases in Sr content for the duration of the fish's life. Small and large forms of Lake Hazen charr of unknown life histories exhibited Sr profiles that were similar to those of the known non-anadromous charr, which strongly suggests that Lake Hazen charr are non-anadromous. These results indicate that Lake Hazen is a "closed" system with energy cycling primarily within the system; this conclusion suggests that a conservative approach would be appropriate for the management of the Lake Hazen charr population. [ABSTRACT FROM AUTHOR]

Previous work found that an earlier ice breakup favors the recruitment of juvenile polar cod (Boreogadus saida) by enabling early hatchers to survive and reach a large size by late summer thanks to a long growth season. We tested the hypothesis that, in addition to a long growth season, an earlier ice breakup provides superior feeding conditions for young polar cod by enhancing microalgal and zooplankton production over the summer months. Ice cover and surface chlorophyll a were derived from satellite observations, and zooplankton and juvenile cod biomass were estimated by hydroacoustics in ten regions of the Canadian Arctic over a period of 11 years. Earlier breakups resulted in earlier phytoplankton blooms. Zooplankton backscatter in August increased with earlier breakup and bloom, and plateaued at chlorophyll a > 1 mg m−3. Juvenile cod biomass in August increased with an earlier breakup, and plateaued at a zooplankton backscatter > 5 m2 nmi−2, supporting the hypothesis that higher food availability promotes the growth and survival of age-0 fish in years of early ice melt. However, there was little evidence that late summer biomass of either zooplankton or age-0 polar cod benefitted from ice breakup occurring prior to June. On average, zooplankton standing stock was similar in the Southern Beaufort Sea and the North Water-Lancaster Sound polynya complex, but juvenile cod biomass was higher in the Beaufort Sea. Intense avian predation could explain the lower biomass of juvenile cod in the polynya complex, confirming its reputation as a biological hotspot for energy transfer to higher trophic levels. [ABSTRACT FROM AUTHOR]

Objectives: Existing information on Arctic marine food web structure is fragmented. Integrating data across research programs is an important strategy for building a baseline understanding of food web structure and function in many Arctic regions. Naturally-occurring stable isotope ratios of nitrogen (δ15N) and carbon (δ13C) measured directly in the tissues of organisms are a commonly-employed method for estimating food web structure. The objective of the current dataset was to synthesize disparate δ15N, and secondarily δ13C, data in the Canadian Beaufort continental shelf region relevant to trophic and ecological studies at the local and pan-Arctic scales. Data description: The dataset presented here contains nitrogen and carbon stable isotope ratios (δ15N, δ13C) measured in marine organisms from the Canadian Beaufort continental shelf region between 1983 and 2013, gathered from 27 published and unpublished sources with associated sampling metadata. A total of 1077 entries were collected, summarizing 8859 individual organisms/samples representing 333 taxa across the Arctic food web, from top marine mammal predators to primary producers. [ABSTRACT FROM AUTHOR]

We assessed the fish length – otolith length relationship (FL–OL) in Dolly Varden (Salvelinus malma malma) to verify proportional growth. A decoupling was detected during first ocean migration where fish growth was occurring at a greater rate than otolith growth. Because of this decoupling, the application of traditional back-calculation models overestimated the size-at-age in premigratory char. We developed modified back-calculation equations from existing traditional models to account for this decoupling based on discontinuous piecewise regressions. The new biological intercept breakpoint method (BI–BP) provided the most accurate representation of fish size-at-age throughout all life history stages when compared with known size-at-capture values in fish. The decoupling indicates that factors other than somatic growth are important for otolith accretion. Physiological changes during smoltification likely alter calcium uptake and thereby affect calcium deposition rates on otoliths during this short but biologically critical time period of life history. It is probable that species exhibiting similar complex ontogenetic shifts in life history will likely exhibit decoupling to some extent in the FL–OL relationship. [ABSTRACT FROM AUTHOR]

The interaction between an organism and its environment is a major determinant of an individual's growth rate, longevity, and fitness. Such interactions and resultant variation in growth is particularly prevalent in salmonids where a diversity of life history types and morphotypes can be observed within a single ecosystem. Lake trout, Salvelinus namaycush, are typically considered freshwater residents. However, three life history types within the Husky Lakes estuary and connected lakes, NWT were recently documented, including semi-anadromous, brackish-water resident, and freshwater resident. To understand how use of brackish-water environments influences growth and longevity in lake trout, we assessed otolith increment widths, as a proxy for annual fish growth, and age-at- capture among life history types. Assessment of increments indicated that growth increased in brackish water for semi-anadromous lake trout, and that growth was faster for semi-anadromous and brackish-water residents than for freshwater residents (70 mm larger on average at age 15). In addition, age at capture was significantly older in brackish-water residents (3.8 years older) when compared to the other life histories. Together these results indicate that life in brackish water can have positive effects on growth and longevity for lake trout. [ABSTRACT FROM AUTHOR]

Partial anadromy is common within salmonid populations, where resident and anadromous individuals interbreed and overlap in habitat use during portions of life. Deviation to this definition occurs within the Husky Lakes drainage basin (HLDB), Northwest Territories, where freshwater resident, semi-anadromous, and brackish-water resident lake trout ( Salvelinus namaycush) life history types are documented. In this study, microsatellite DNA variation was assayed to evaluate genetic structuring among life history types from the HLDB and adjacent lower Mackenzie River system. Significant differentiation was resolved among most locations and life histories (global FST = 0.192). Brackish-water residents were differentiated from all locations and life histories, including sympatric semi-anadromous individuals, providing evidence for genetically fixed strategies. Also, this provides the first evidence of breeding partial migration in salmonids using brackish-water environments, where brackish-water residents and semi-anadromous migrants interact during the nonbreeding season, but the latter migrate elsewhere to spawn. Alternatively, the lack of genetic differentiation between semi-anadromous and Sitidgi Lake residents suggests conditional mating tactics may also influence partial anadromy. This work provides novel insights into partial anadromy in Arctic salmonids and expands our knowledge of biodiversity in this region. [ABSTRACT FROM AUTHOR]

Trophic patterns for Greenland Halibut are reported for the first time in the Canadian Beaufort Sea and Amundsen Gulf ( n  = 269). Samples were collected from 2012 to 2014 on the upper (300–500 m) and lower continental slope (750–1500 m) and were analyzed for stomach contents, stable isotopes ratios and fatty acids (FA). Stomach contents indicated that Arctic Cod, Boreogadus saida , was the main prey ingested on the upper slope (50–94% of total biomass) whereas Gelatinous Snailfish ( Liparis fabricii ) and Zoarcids ( Lycodes spp .) dominated diets on the lower slope (17–62% of total biomass). Stable isotope mixing models and FA analyses also identified benthopelagic fishes (i.e., Liparis spp ., B . saida ) as key prey and highlighted large dietary overlap among years and between the two depth categories. Greenland Halibut were characterized by relatively wide δ 13 C and narrow δ 15 N ranges that suggested use of both pelagic and benthic energy sources and a piscivorous diet. Calanus -type markers such as 20:1n9 dominated the FA (>20% of total FA) andemphasized the importance of pelagic-derived material in the diet. The contribution of pelagic and benthic-derived matter in the diet suggests that Greenland Halibut play a major role in the benthic-pelagic coupling for deep water communities (up to 1500 m) in the Canadian Beaufort Sea. [ABSTRACT FROM AUTHOR]

Accumulation of trimethylamine N-oxide (TMAO) by deep-sea animals is proposed to protect proteins against the destabilizing effects of high hydrostatic pressure (the piezolyte hypothesis). Chondrichthyan fishes (sharks, rays, and chimaeras) provide a unique test of this hypothesis because shallow-living species have elevated TMAO levels to counteract the destabilizing effects of high urea levels accumulated for osmoregulation. Limited interspecific studies of chondrichthyans reveal that increasing depth correlates with decreased urea and increased TMAO levels, suggesting a dynamic balance between destabilizing forces on proteins (high urea, hydrostatic pressure) and TMAO to counteract these forces. Indeed, an inability to minimize urea levels or maximize TMAO levels has been proposed to explain why chondrichthyans are absent in the vast abyssal region. An unresolved question is whether the depth-related changes in chondrichthyan osmolytes are a flexible response to depth or whether phylogenetic differences in species-specific physiological set points for osmolytes account for the differences seen with depth. Sampling Arctic skates (Amblyraja hyperborea) across a 1,015-m depth gradient in the Beaufort Sea, we measured organic osmolytes in muscle using spectrophotometry and high-performance liquid chromatography. We found that the urea-to-TMAO ratio decreased linearly with depth, with tighter correlation than that seen in interspecific studies. Minor osmolytes, including betaine, sarcosine, and some α-amino acids, also declined with depth, apparently replaced (as with urea) by TMAO (a stronger piezolyte than those solutes). These data provide the first intraspecific evidence that flexible adjustments of osmolyte combinations are a key response for deep-sea living in individual chondrichthyans, supporting the piezolyte hypothesis. [ABSTRACT FROM AUTHOR]

Zebra mussel Dreissena polymorpha (Pallas, 1771), an invasive bivalve in North America, was first recorded in Lake Winnipeg in 2013. Quagga mussel D. bugensis (Andrusov, 1897), a second invasive mussel to North America, has yet to be detected in Manitoba waters. The establishment and continued spread of zebra mussels is of concern. Accordingly, we developed two species-specific and one Dreissena-specific qPCR-based environmental DNA (eDNA) assays designed as a single multiplexed reaction able to identify the presence of zebra mussel and infer the presence of quagga mussel in water samples from at-risk and invaded locations. In 2014, samples were collected from four invaded harbours on Lake Winnipeg during the early (May) and late (October) seasons. Zebra mussel eDNA was detected in 0–33.3% of samples per site early in the season, whereas late season sample detection ranged from 42.9 to 100%. In order to confirm that there was no nonspecific amplification of DNA from local biota, samples were also collected from sites where neither adult nor veliger-stage zebra mussels had been previously observed. These sites included three harbours on Lake Winnipeg and six sites within the Manitoban portion of the Red River. No amplification of eDNA was recorded at these sites except for that at a float-plane dock in the Red River upstream of Lake Winnipeg. Zebra mussels were subsequently detected at this location by sampling for transformed attached individuals. Thus, we demonstrate that eDNA is an early indicator of the presence of zebra mussels and is a useful detection tool at the forefront of their recent invasion in Manitoba. This work provides the foundation for the development of a zebra mussel eDNA monitoring program for waterbodies in Manitoba and western Canada. [ABSTRACT FROM AUTHOR]

Polar cod ( Boreogadus saida ) is the dominant forage fish in Arctic seas and the main prey of the ringed seal ( Pusa hispida ), the beluga ( Delphinapterus leucas ) and several seabird species. Changes in the abundance of polar cod will have cascading effects on arctic marine ecosystems. We tested the hypothesis that an earlier sea ice breakup and warmer sea surface temperatures (SST) in spring-summer result in the higher recruitment of juvenile polar cod in late summer. The density (number m −2 ) and biomass (mg m −2 ) of age-0 polar cod in August and September, estimated by hydroacoustics over 9 years in 9 areas of the Canadian Arctic, were negatively correlated to ice breakup week and positively correlated to SST. The timing of the ice breakup was the main determinant of recruitment, with mean juvenile biomass in September up to 11 times greater for early breakup (late May) than for late breakup (early September). Early ice breakup in spring increased juvenile biomass in August and September by allowing the survival of larvae hatched in winter and spring. Since 1979, ice breakup has occurred earlier by as much as 9.3 days per decade in some areas. We thus forecast a transient increase in polar cod biomass over the first part of the present century. Thereafter, the relaxation of extreme climatic conditions in Arctic seas should harbinger the replacement of the hyper-specialized polar cod by subarctic and boreal forage fish. [ABSTRACT FROM AUTHOR]

Marine fishes in the Canadian Beaufort Sea have complex interactions with habitats and prey, and occupy a pivotal position in the food web by transferring energy between lower- and upper-trophic levels, and also within and among habitats (e.g., benthic-pelagic coupling). The distributions, habitat associations, and community structure of most Beaufort Sea marine fishes, however, are unknown thus precluding effective regulatory management of emerging offshore industries in the region (e.g., hydrocarbon development, shipping, and fisheries). Between 2012 and 2014, Fisheries and Oceans Canada conducted the first baseline survey of offshore marine fishes, their habitats, and ecological relationships in the Canadian Beaufort Sea. Benthic trawling was conducted at 45 stations spanning 18–1001 m depths across shelf and slope habitats. Physical oceanographic variables (depth, salinity, temperature, oxygen), biological variables (benthic chlorophyll and integrated water-column chlorophyll) and sediment composition (grain size) were assessed as potential explanatory variables for fish community structure using a non-parametric statistical approach. Selected stations were re-sampled in 2013 and 2014 for a preliminary assessment of inter-annual variability in the fish community. Four distinct fish assemblages were delineated on the Canadian Beaufort Shelf and slope: 1) Nearshore-shelf: <50 m depth, 2) Offshore-shelf: >50 and ≤200 m depths, 3) Upper-slope: ≥200 and ≤500 m depths, and 4) Lower-slope: ≥500 m depths. Depth was the environmental variable that best explained fish community structure, and each species assemblage was spatially associated with distinct aspects of the vertical water mass profile. Significant differences in the fish community from east to west were not detected, and the species composition of the assemblages on the Canadian Beaufort Shelf have not changed substantially over the past decade. This community analysis provides a framework for testing hypotheses regarding the trophic dynamics and ecosystem roles of Beaufort Sea marine fishes, including biological linkages (i.e., fish movements and trophic interactions) among offshore habitats. Understanding regional-scale habitat associations will also provide context to identify potentially unique and/or sensitive habitats and fish community characteristics, thus aiding identification of ecologically and biologically significant areas, and to inform conservation efforts. [ABSTRACT FROM AUTHOR]

Distributional shifts of biota to higher latitudes and elevations are presumably influenced by species-specific physiological tolerances related to warming temperatures. However, it is establishment rather than dispersal that may be limiting colonizations in these cold frontier areas. In freshwater ecosystems, perennial groundwater springs provide critical winter thermal refugia in these extreme environments. By reconciling the thermal characteristics of these refugia with the minimum thermal tolerances of life stages critical for establishment, we develop a strategy to focus broad projections of northward and upward range shifts to the specific habitats that are likely for establishments. We evaluate this strategy using chum salmon ( Oncorhynchus keta) and pink salmon ( Oncorhynchus gorbuscha) that seem poised to colonize Arctic watersheds. Stream habitats with a minimum temperature of 4 °C during spawning and temperatures above 2 °C during egg incubation were most vulnerable to establishments by chum and pink salmon. This strategy will improve modelling forecasts of range shifts for cold freshwater habitats and focus proactive efforts to conserve both newly emerging fisheries and native species at northern and upper distributional extremes. [ABSTRACT FROM AUTHOR]

The northern Dolly Varden ( Salvelinus malma malma) displays variable life-history types and occupies freshwater habitats with varying levels of connectivity. Here, we assayed microsatellite DNA variation in northern Dolly Varden from the western Canadian Arctic to resolve landscape and life-history variables driving variation in genetic diversity and population structure. Overall, genetic variation was highest in anadromous populations and lowest in those isolated above waterfalls, with stream-resident forms intermediate between the two. Anadromous and isolated populations were genetically divergent from each other, while no genetic differentiation was detectable between sympatric anadromous and stream-resident forms. Population structure was stable over 25 years, hierarchically organized, and conformed to an isolation-by-distance pattern, but stream-isolated forms often deviated from these patterns. Gene flow occurred primarily among Yukon North Slope populations and between sympatric anadromous and resident forms. These results were sex-dependent to some extent, but were influenced more by reproductive status and life history. Our study provides novel insights into the life history, population demographic, and habitat variables that shape the distribution of genetic variation and population structure in Arctic fluvial habitats while providing a spatial context for management and conservation. [ABSTRACT FROM AUTHOR]

Considerable progress has been made in the development of statistical tools to quantify trophic relationships using stable isotope ratios, including tools that address size and overlap of isotopic niches. We build upon recent progress and propose a new probabilistic method for determining niche region and pairwise niche overlap that can be extended beyond two dimensions, provides directional estimates of niche overlap, accounts for species-specific distributions in niche space, and, unlike geometric methods, produces consistent and unique bivariate projections of multivariate data. We define the niche region (NR) as a given 95% (or user-defined α) probability region in multivariate space. Overlap is calculated as the probability that an individual from species A is found in the NR of species B. Uncertainty is accounted for in a Bayesian framework, and is the only aspect of the methodology that depends on sample size. Application is illustrated with three-dimensional stable isotope data, but practitioners could use any continuous indicator of ecological niche in any number of dimensions. We suggest that this represents an advance in our ability to quantify and compare ecological niches in a way that is more consistent with Hutchinson's concept of an ''ndimensional hypervolume. [ABSTRACT FROM AUTHOR]

In 2012, Arctic cod (Boreogadus saida) were collected from offshore regions of the Beaufort Sea to determine the concentrations of CYP1A1 phase I metabolites of polycyclic aromatic hydrocarbons (OH-PAHs) in liver and to correlate measured concentrations with (i) morphometric measurements that are known to be indicative offish health and, (ii) biochemical end points of health including vitamin A/E and metabolites and hepatic deiodinase activity (DI). Four ring OH-PAHs were detected in 90% of our samples with a mean liver concentration of 1829.2 ± 159.2 ng/g (ww). Total (Σ) concentrations of 5/6-membered ring OH-PAHs in liver were smaller [mean of 931.6 ± 104.3 ng/g, (ww)] and detected less frequently (75%) than the 4-ring OH-PAHs. Fish length and liver weight were both negatively correlated to Σconcentrations of 4-ringed OH-PAHs (p < 0.001). Liver somatic index was also negatively correlated to Σ4-OH-PAHs (p < 0.05) but not for Σ5/6-OH-PAHs (p > 0.1). There was a significant positive relationship between DI and 4-ring OH-PAHs (p < 0.05) in liver, suggesting an induction of this enzyme. No such correlation was observed for the 5/6-ring OH-PAHs. Retinyl palmitate (RP) was the only vitamin that could be measured in liver ranging from 0.230 to 26.3 ug/g (ww). No associations between RP and levels of the 4- or 5/6-ringed OH-PAHs were observed Continued baseline studies are clearly warranted to further understand effects of OH-PAHs on fish health before planned exploration activities begin in this region. [ABSTRACT FROM AUTHOR]

The taxonomy of the North American ciscoes ( Salmoniformes: Coregonidae) remains unresolved. We provide the first comprehensive description of the Great Slave Lake ciscoes. Our analysis supports the hypothesis that the Great Slave Lake cisco complex includes at least two nominate species ( Coregonus artedi and Coregonus sardinella) and an adfluvial C. artedi morph that is distinct from its lacustrine conspecific in terms of life history, morphology, age, growth and mortality. Coregonus sardinella has previously been identified from Great Slave Lake, but we provide the first comprehensive description of this species in the lake and confirm a significant range extension for the species. The lacustrine C. artedi differs little from descriptions throughout its range. In addition to these three ciscoes, linear phenotypic traits, gillraker number and morphology, and growth data support the possible occurrence of two other, less-distinct morphs, the big-eye cisco and a shortjaw-like morph Coregonus zenithicus. Although the big-eye morph was not identified by body shape and linear phenotypic measures, it was visually identified on the basis of differences in traditional phenotypic proportions, such as orbital length, paired fin lengths, head and gillraker morphology expressed as thousands of standard length and showed different age and growth structure compared with the other lacustrine cisco morphs. Coregonus zenithicus was distinguished visually and by a statistical model of linear phenotypic traits as well as by gillraker number and morphology. Identifying, characterising and managing locally adapted cisco morphs that reflect important ecological and bioenergetic linkages are critical to conserving the ecological integrity of northern ecosystems. [ABSTRACT FROM AUTHOR]

Assessment of population structure is critical to the design and implementation of sound management and conservation strategies. However, population structure must be assessed using markers attuned to population genetic processes such as genetic drift and gene flow, which reflect actual levels of reproductive isolation among putative genetic clusters. This is critical for highly exploited, commercial species that form the backbone of regional and local economies. Here, we show extremely low levels of population genetic differentiation among Greenland halibut ( Reinhardtius hippoglossoides) collected from throughout the Northwest Atlantic, which cannot be statistically differentiated from panmixia using 12 species-specific polymorphic microsatellite markers. In contrast, some previous studies have demonstrated significant differences among individuals collected from various parts of the species' range using a variety of both genetic and nongenetic techniques. In accordance with other reports and consistent with the species' life history, we demonstrate that the most parsimonious explanation reconciling observed patterns is a repeated high degree of local differentiation of new recruits and colonizers originating from a common gene pool. Such a scenario has important conservation implications in terms of devising more appropriate strategies balancing species persistence and replenishment with sustainable resource use. [ABSTRACT FROM AUTHOR]

Abstract: This study examines the community structure of demersal marine fishes on the Canadian Beaufort Shelf and at Herschel Island, Yukon Territory. Fishes were sampled along five transects during the summers of 2006–2009 to assess community structure. Environmental parameters were documented to examine habitat associations of fishes. Results indicate a shift in community composition at approximately 50m depth in both areas, forming distinct shallow and deepwater assemblages. A subset of species define the assemblages, with Gymnocanthus tricuspis and Ulcina olrikii typifying the <50m and >50m groups, respectively, on the shelf. At Herschel Island, U. olrikii did not typify the >50m group, suggesting differences in species composition relative to Canadian Beaufort Shelf transects. However, differences in community composition between the two areas were not statistically significant. Boreogadus saida were common to shallow and deep assemblages. Depth and salinity best grouped the sites in a manner consistent with species' abundances on the Canadian Beaufort Shelf. Attempts to match biotic data with environmental parameters at Herschel Island stations were not conclusive. Investigation is required into the role of larger scale processes (e.g., upwelling events, ice-scouring, and plume dynamics) in driving the distributions of marine fishes in the Beaufort Sea. [Copyright &y& Elsevier]

Perfluorinated chemicals (PFCs) have been recorded in many types of marine and freshwater ecosystems. The aim of the present study was to examine meromictic lakes and their catchments on the far northern coast of Ellesmere Island, Nunavut, Canada, and to evaluate the results in the context of climate change. Our analyses revealed the presence of several PFCs in catchment snowpack, inflowing streams, lake water, and the aquatic food web of Lake A (83°00' N, 75°30' W), showing that dispersal of these contaminants reaches the northern limit of the terrestrial High Arctic. However, the concentrations were low (total PFCs: 27 - 754 pg L-1 for water, 134 - 848 pg L-1 for melted snow, 5 - 2149 pg g-1 wet weight for fish; PFOS: 66 pg g-1 dry weight in surficial sediments) and at or below values reported to date in the literature for other remote lakes. PFHpA, PFOA, and PFNA were the main compounds detected in water and melted snow, while PFNA, PFDA, and PFUnA were the predominant compounds in the aquatic biota, indicating their bioaccumulative potential. Salinity-temperature-depth profiles suggested that most of the present contaminant load enters the lake via streams and flows directly under the lake ice to the ocean. The onset of summer open water in this perennially ice-covered lake in response to climate warming, and the increased duration of open water in recent years, have implications for the distribution, transport, and retention of PFCs in Arctic lakes. [ABSTRACT FROM AUTHOR]

Pingualuk Lake fills a deep crater in the Parc National des Pingualuit on the Ungava Peninsula (Nunavik, Canada) and is isolated from nearby surface waters. The main objectives of this study were to determine and compare the concentrations of two atmospherically derived contaminants, mercury and perfluorinated chemicals (PFCs), in the lake water column and fish of Pingualuk Lake and to assess the physical and biological factors influencing contaminant concentrations. Mercury concentrations in arctic char muscle tissue were comparable to those of char in other Arctic lakes, while the total amount of PFCs was below reported levels for remote lakes in the Arctic and elsewhere. Stable isotope and stomach content analyses were made to investigate the feeding ecology of the Pingualuk Lake arctic char population and indicated the possibility of multiple feeding groups. Genetics characteristics (MH and mtDNA) of fish from Pingualuk Lake revealed that this population is likely distinct from that of nearby Laflamme Lake. However, both arctic char populations exhibit differential variation of their allele families. Physical characteristics determined for Lake Pingualuk revealed that the water column was inversely stratified beneath the ice and extremely transparent to visible and ultraviolet radiation. The highest mercury concentrations (3-6 pg mL-1 THg) occurred just beneath the ice surface in each lake. Pingualuk Lake, given its near pristine state and exceptional limnological features, may serve as a most valuable reference ecosystem for monitoring environmental stressors, such as contaminants, in the Arctic. [ABSTRACT FROM AUTHOR]