High Arctic Lake Research Articles

The potential of oviduct tags and fine-scale acoustic telemetry to reveal the timing and location of spawning in Arctic salmonids (Salvelinus spp.).

Identifying and characterizing spawning locations are paramount for the protection of critical fish habitats but can be challenging, particularly in remote locations. Using the underexplored oviduct-tagging technique, we aimed to identify the timing and location of spawning for wild Arctic char (Salvelinus alpinus) and lake trout (Salvelinus namaycush) in two high-Arctic lakes in Nunavut. Specifically, Innovasea V7 acoustic telemetry transmitters were inserted into the oviducts of 13 Arctic char and 4 lake trout, and the timing and location of tag expulsion were determined using a fine-scale positioning system. Twenty Arctic char and 20 lake trout were also tagged with abdominal V16 transmitters, and 10 of them were paired with the oviduct tags, to further study the behavior of individual fish during the spawning season. Oviduct tags from four Arctic char and one lake trout could be used to assess the timing and location of spawning. Spawning anadromous Arctic char drastically reduced their activity and remained proximate to their presumed spawning location immediately before and for months after spawning. In contrast, a non-anadromous (i.e., freshwater resident) Arctic char and a lake trout showed little to no reduction in activity around presumed spawning events. Because of the highlighted sedentary behavior of inferred spawning anadromous Arctic char implanted with both abdominal and oviduct tags, we could also infer potential spawning based on the behavior of individuals equipped only with abdominal tags. Spawning areas identified via telemetry also aligned well with Inuit knowledge of those lakes. This is the first field study to use acoustic oviduct and abdominal tags coupled with a fine-scale positioning system. Despite a limited success rate of ejection, the study reveals the strong potential of the method to study spawning habitat and timing, particularly in remote areas.

Marine organisms transported by seabirds may contribute significantly to Arctic charr diet in coastal High-Arctic lakes

The rich marine resources along the western coast of Spitsbergen (Svalbard) have given rise to colonies of breeding seabirds, which likely represent an important vector of nutrient transport from marine to terrestrial environments. These seabirds may also supply additional nutrients to lakes via their droppings, while bathing and/or when being attacked by other birds during flight to their nest sites. To study the importance of such droppings in the diet of freshwater fish, we sampled Arctic charr by gillnetting during a three-week period in the oligotrophic Lake Arresjøen in northwestern Svalbard. Marine fish and invertebrates made up more than 12% of the dry weight of the stomach contents of Arctic charr larger than 24 cm captured in the littoral zone. This suggests that the seabird transport of marine organisms contributes directly to the diet of Arctic charr in coastal High-Arctic lakes, but this contribution may also give a higher load of mercury and polychlorinated compounds.

Mysis segerstralei, an unexpected but important prey for resident Arctic charr (Salvelinus alpinus) in a Svalbard lake

Mysis segerstralei is distributed over a wide geographic area and in habitats with a variety of salinity conditions, including marine and brackish waters around Svalbard. The species has seldom been found in freshwater lakes, and the discovery of M. segerstralei in Lake Pulmankijärvi at the border between Northeastern Norway and Finland, may represent the single known freshwater occurrences in western Europe. Svalbard lake systems are characterized by very low water temperatures, long-term ice cover, and low levels of nutrients. Food is thus limited, and chironomids generally dominate the stomach contents in Arctic charr, the only freshwater fish species on Svalbard. Based on several surveys in more than 30 of Svalbard lakes over many decades, M. segerstralei has only been found as food for Arctic charr in Lake Vårfluesjøen. In a later fishery survey, we studied the diet of Arctic charr in this lake. The stomach contents from Arctic charr sampled in the profundal habitats were dominated by M. segerstralei, but the species was also among the most frequent prey items in the littoral and pelagic habitats. This unexpected occurrence of M. segerstralei demonstrates the high importance of mysids even in a low-productive, High Arctic lake.

Landscape evolution and sediment delivery in a High Arctic proglacial lake, Ellesmere Island, Canadian Arctic Archipelago

AbstractGeophysical and morphosedimentary investigations were conducted at Strathcona Lake, a High Arctic proglacial lake and its catchment connected to the Taggart Lake Glacier, northwest corner of the Prince of Wales Icefield in Ellesmere Island (eastern Canadian Arctic Archipelago). The mapping of glaciomarine landforms and units provides, together with updated radiocarbon information, a framework for catchment evolution and sediment delivery to the lake during deglaciation and glacio‐isostatically induced relative sea level fall. A staircase of deltas with descending altitudes provide evidence for a spatially diachronous timing of ice retreat from the catchments around Strathcona Lake. Swath bathymetric mapping coupled with acoustic sediment stratigraphy show draped infills with a transition from marine to rhythmically bedded lacustrine sediments produced by hyperpycnal flows. Multiproxy investigations on a set of sediment cores highlight proglacial varves interrupted by rhythmites resulting from the erosion of fluvially incised glaciomarine sediments stored in the catchment. Pluricentimetric proglacial varves formed during the last century in response to periods of intense glacial melt, notably since the 21st century. The sedimentary record suggests the varved sediments from Strathcona Lake can be used to reconstruct the melting history of the Prince of Wales Icefield. This work provides a geomorphological, sedimentological, and geochemical framework that should guide future varve‐based reconstructions of glacial and climatic variability in Ellesmere Island.

Regime Shifts in Lake Oxygen and Temperature in the Rapidly Warming High Arctic

AbstractGlobal warming is destabilizing the cryosphere, with consequences for glaciers, permafrost, sea ice and lake ice. Polar lakes have short ice‐free seasons, and small changes in ice cover duration have the potential to provoke alterations to ecosystem structure. However, these lakes are understudied, and the consequences for mixing regimes, thermal structures and biogeochemical processes remain unclear. We measured three annual cycles of dissolved oxygen, temperature and specific conductivity in a lake at ∼83°N to investigate limnological processes and their interannual variability. There were sharp interannual contrasts in lake dynamics, with state shifts in mixing, stratification and oxygen regimes due to air temperature variability and meteorological events. We also observed unusual thermal profiles that were associated with solute gradients. These striking differences underscore the sensitivity of high Arctic lakes to interannual variations in meteorological forcing, and their susceptibility to regime shifts in response to ongoing global change.

Long‐term phytoplankton dynamics in two High Arctic lakes (north‐east Greenland)

Abstract Primary producers form the base of lake ecosystems and, due to their often short lifecycles, respond rapidly to changing conditions. As the Arctic is warming nearly four times faster than the global average, we see major shifts in environmental conditions, which impacts lake ecosystem functioning. Previous studies have found a general increase in primary productivity due to climate warming. However, few long‐term studies have included changes in phytoplankton community composition and biomass in relation to warming in Arctic lakes and it therefore remains unclear how different algal taxa and thus the community respond. We investigated how climate warming affects phytoplankton community composition, taxon richness and biomass in High Arctic lakes, using a unique 23‐year data series on phytoplankton in two shallow lakes at Zackenberg, north‐east Greenland, one with Arctic charr (Salvelinus alpinus) and one without fish. We further elucidated the role of physico‐chemical variables and zooplankton grazers in the changes observed. Few major changes were observed in phytoplankton community composition over time, but the year‐to‐year variation was large. Taxon richness did, however, increase throughout the monitoring period, and in both lakes there was a significant increase in diatom biomass coinciding with increasing conductivity. Additionally, phytoplankton biomass was greater during warmer years with earlier ice melt. We further found that nutrient levels were positively associated with the total phytoplankton biomass in both lakes, indicating that expected increased nutrient levels, due to climate change, may lead to a greater phytoplankton biomass in High Arctic lakes in the future. The large year‐to‐year variability, in both climate and environmental conditions, makes it difficult to predict weather patterns and their consequences for lake ecosystems in the Arctic region. This underlines the importance of long‐term monitoring programmes across the circumpolar Arctic and collaboration across regions and institutes within large scale studies.

Exotic pollen in sediments from the high Arctic Lake Tenndammen, Svalbard archipelago: diversity, sources, and transport pathways

We analysed the pollen and spores extracted from 73 samples of lacustrine sediments from Colesdalen in Svalbard (Lake Tenndammen) as well as 10 soil samples collected from the lake’s shores. In total, 56 pollen taxa were recorded from the sediments spanning the last 800 years, whilst 35 pollen types were found in the soil samples. Pollen was categorised as (i) regional (from Svalbard); (ii) exotic to Svalbard today; or (iii) of mixed or unclear origin. Major changes in pollen assemblages after ca 1900 CE were associated with human impact. Around 1920 CE, the first signs of introduced plant taxa were identified, by the presence of Apiaceae and Fabaceae pollen. Additionally, large-sized pollen with a thick exine and annulus diameter of 10.6–13 μm, identified as Poaceae/Cerealia type, was constantly present after ca 1920 CE. Other exotic pollen, including Ulmus, Juglans, and tropical pollen of Albizia/Mimosa type, Eucalyptus type, Acalypha type, and Passiflora type, are found only during the 1930s to 1960s, which is the period associated with the most intensive mining activity and human migration to and from Colesdalen. Furthermore, the repeated occurrence of Myrica (gale) type and Erica type occurring both in the lake sediment and in the soil samples is best explained by the migration of geese from Scotland (UK). Our research demonstrates how precisely human history can be reflected in the lake sediments of the Arctic environment.

Divergent Temporal Trends of Mercury in Arctic Char from Paired Lakes Influenced by Climate-Related Drivers.

Climate-driven changes including rising air temperatures, enhanced permafrost degradation, and altered precipitation patterns can have profound effects on contaminants, such as mercury (Hg), in High Arctic lakes. Two physically similar lakes, East Lake and West Lake at the Cape Bounty Arctic Watershed Observatory on Melville Island, Nunavut, Canada are being affected by climate change differently. Both lakes have experienced permafrost degradation in their catchments; however, West Lake has also undergone multiple underwater Mass Movement Events (MMEs; beginning in fall 2008), leading to a sustained 50-fold increase in turbidity. This provided the unique opportunity to understand the potential impacts of permafrost degradation and other climate-related effects on Hg concentrations and body condition of landlocked Arctic char (Salvelinus alpinus), an important sentinel species across the Circum-Arctic. Our objectives were to assess temporal trends in char Hg concentrations and to determine potential mechanisms driving the trends. There was a significant decrease in Hg concentrations in East Lake char, averaging 6.5%/year and 3.8%/year for length-adjusted and age-adjusted means, respectively, from 2008 to 2019. Conversely, in West Lake there was a significant increase, averaging 7.9%/year and 8.0%/year for length-adjusted and age-adjusted mean Hg concentrations, respectively, for 2009 to 2017 (the last year with sufficient sample size). The best predictors of length-adjusted Hg concentrations in West Lake were carbon and nitrogen stable isotope ratios, indicating a shift in diet including possible dietary starvation brought on by the profound increase in lake turbidity. Our study provides an example of how increasing lake turbidity, a likely consequence of climate warming in Arctic lakes, may influence fish condition and Hg concentrations. Environ Toxicol Chem 2023;42:2712-2725. © 2023 His Majesty the King in Right of Canada and The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada.

Evidence of summer thermal stratification in extreme northern lakes

Rapid warming in the High Arctic has induced changes in terrestrial environments that have included major recent shifts in lakes and ponds. Numerous studies exist of spatial trends in water chemistry, bioindicator groups, and paleoenvironmental change from High Arctic lakes; however, little is known about lake thermal stratification regimes at high latitudes beyond assumptions based on generalized classification schemes. Here, we report on the presence in late July 2022 of positive thermal stratification during open-water conditions in two freshwater lakes near Clements Markham Inlet, on northern Ellesmere Island. These lakes are situated in the polar desert at 82.6°N, >1000 km north of the generally accepted northern limit of summer thermal stratification. Given their location approaching the northernmost land on Earth, the thermal profiles of these lakes suggest that the occurrence of summer stratification may no longer be discounted anywhere in the Northern Hemisphere.

A ∼5000 year multiproxy record of summer climate in NE Greenland

The High Arctic plays a vital role in Earth's climate system, and its ecosystems are highly sensitive to global climate change. High Arctic lakes are valuable sentinels of climate change, as their sediments integrate long-term natural climatic fluctuations and anthropogenic influences. Here, we present a high-resolution ∼5000 year-reconstruction of NE Greenland climate variability from Aucella Lake (74°N, 20°E) based on physical, chemical, and biological properties of lake sediments. We use CT-scans, hyperspectral imaging, organic matter, XRD, and diatom analyses to show that changing air temperatures were controlled by a mix of regional climatic changes and local landscape feedbacks. The latest Mid-Holocene (∼5.0–3.8 cal. ka BP) was characterized by relatively warmer conditions, while the onset of the Late-Holocene was marked by abrupt temperature decreases that coincided with the beginning of glacial advances elsewhere (∼3.8–3.4 cal. ka BP). From ∼3.4–2.4 cal. ka BP, the sedimentary record indicated progressive warming, with temperature peaking during the Medieval Climate Anomaly, although temperature rises were punctuated by abrupt, short-lived cold periods. From ∼1.1–0.05 cal. ka BP, the influence of landscape factors over the system diminished. Sedimentary indicators suggested a transition towards a colder, more humid climate, coinciding with the beginning of the Little Ice Age, that was characterized by a marked decrease in air temperature that reached minimum values at the end of this period. The last 50 years at Aucella Lake were marked by abrupt temperature rises, consistent with recently observed anthropogenic global warming. Our results illustrate the importance of high-resolution multiproxy studies for accurately characterizing lake linkages to their environment and climate.

Characterization of skin- and intestine microbial communities in migrating High Arctic lake whitefish and cisco

At high latitudes, lake whitefish ( Coregonus clupeaformis) and others in the closely related Coregonus species complex (CSC) including cisco ( C. autumnalis and C. sardinella) can be diadromous, seasonally transitioning between freshwater lakes and the Arctic Ocean. CSC skin- and intestine microbiomes were collected, facilitated by Inuit fishers at sites on and around King William Island, Nunavut, at the northern range limits of lake whitefish. Community composition was explored using 16S rRNA gene sequencing and microbiota distinctly grouped depending on fishing site salinity. Overall, lake whitefish intestine communities were more variable than those of the two cisco with higher Shannon diversity, suggesting that lake whitefish and their microbiomes could be susceptible to environmental stress possibly leading to dysbiosis. Lake whitefish showed lower condition (K) in the ocean than in freshwater rivers, whereas cisco condition was similar among distinct seasonal habitats. Taken together, the impact of changing habitats on fish condition and microbial composition may inform approaches to CSC health in fisheries and aquaculture, in addition to being relevant for northern Indigenous peoples with subsistence and economic interests in these resources.

Mercury at the top of the world: A 31-year record of mercury in Arctic char in the largest High Arctic lake, linked to atmospheric mercury concentrations and climate oscillations

Lake Hazen, the largest lake north of the Arctic circle, is being impacted by mercury (Hg) pollution and climate change. The lake is inhabited by two morphotypes of land-locked Arctic char (Salvelinus alpinus), a sensitive indicator species for pollution and climatic impacts. The objectives of this study were to describe the trends in Hg concentration over time and to determine the relationship of climate to length-at-age and Hg concentrations in each char morphotype, as well as the relationship to atmospheric Hg measurements at a nearby monitoring station. Results for Hg in char muscle were available from 20 sampling years over the period 1990 to 2021. We found significant declines in Hg concentrations for both morphotypes during the 31-year study period. Increased rain and earlier freeze-up of lake ice during the summer growing season was linked to increased length-at-age in both char morphotypes. For the large morphotype, higher total gaseous Hg in the fall and winter seasons was related to higher concentrations of Hg in char, while increased glacial runoff was related to decreases in char Hg. For the small morphotype char, increased snow and snow accumulation in the fall season were linked to declines in char Hg concentration. The Atlantic Multidecadal Oscillation and Arctic Oscillation were positively related to the large char Hg trend and Arctic Oscillation was positively related to the small char Hg trend. Significant trend relationships between atmospheric Hg and Hg in biota in remote regions are rare and uniquely valuable for evaluation of the effectiveness of the Minamata Convention and related monitoring efforts.

Drivers and variability of CO2:O2 saturation along a gradient from boreal to Arctic lakes

Lakes are significant players for the global climate since they sequester terrestrially derived dissolved organic carbon (DOC), and emit greenhouse gases like CO2 to the atmosphere. However, the differences in environmental drivers of CO2 concentrations are not well constrained along latitudinal and thus climate gradients. Our aim here is to provide a better understanding of net heterotrophy and gas balance at the catchment scale in a set of boreal, sub-Arctic and high-Arctic lakes. We assessed water chemistry and concentrations of dissolved O2 and CO2, as well as the CO2:O2 ratio in three groups of lakes separated by steps of approximately 10 degrees latitude in South-Eastern Norway (near 60° N), sub-Arctic lakes in the northernmost part of the Norwegian mainland (near 70° N) and high-Arctic lakes on Svalbard (near 80° N). Across all regions, CO2 saturation levels varied more (6–1374%) than O2 saturation levels (85–148%) and hence CO2 saturation governed the CO2:O2 ratio. The boreal lakes were generally undersaturated with O2, while the sub-Arctic and high-Arctic lakes ranged from O2 saturated to oversaturated. Regardless of location, the majority of the lakes were CO2 supersaturated. In the boreal lakes the CO2:O2 ratio was mainly related to DOC concentration, in contrast to the sub-Arctic and high-Arctic localities, where conductivity was the major statistical determinant. While the southern part is dominated by granitic and metamorphic bedrock, the sub-Arctic sites are scattered across a range of granitic to sedimentary bed rocks, and the majority of the high-Arctic lakes are situated on limestone, resulting in contrasting lake alkalinities between the regions. DOC dependency of the CO2:O2 ratio in the boreal region together with low alkalinity suggests that in-lake heterotrophic respiration was a major source of lake CO2. Contrastingly, the conductivity dependency indicates that CO2 saturation in the sub-Arctic and high-Arctic lakes was to a large part explained by DIC input from catchment respiration and carbonate weathering.

Viral spillover risk increases with climate change in High Arctic lake sediments.

The host spectrum of viruses is quite diverse, as they can sustainedly infect a few species to several phyla. When confronted with a new host, a virus may even infect it and transmit sustainably in this new host, a process called ‘viral spillover’. However, the risk of such events is difficult to quantify. As climate change is rapidly transforming environments, it is becoming critical to quantify the potential for spillovers. To address this issue, we resorted to a metagenomics approach and focused on two environments, soil and lake sediments from Lake Hazen, the largest High Arctic freshwater lake in the world. We used DNA and RNA sequencing to reconstruct the lake’s virosphere in both its sediments and soils, as well as its range of eukaryotic hosts. We then estimated the spillover risk by measuring the congruence between the viral and the eukaryotic host phylogenetic trees, and show that spillover risk increases with runoff from glacier melt, a proxy for climate change. Should climate change also shift species range of potential viral vectors and reservoirs northwards, the High Arctic could become fertile ground for emerging pandemics.

Monitoring and classification of high Arctic lakes in the Svalbard Islands using remote sensing

Arctic lakes are an essential element of the environment. This study inventoried and classified lakes on three of the Svalbard Islands (Spitsbergen, Barentsøya, and Edgeøya) using Sentinel-2 images. The Forel-Ule color index (FUI) was employed to measure the lake's color, and a new equation to calculate the concentration of suspended sediment using satellite images was developed and tested using measurements from coastal waters. These two measures, plus the normalized difference vegetation index for vegetation on the lakeshore, and the lakes' location were used for clustering and classification. More than 1000 natural lakes were found on the three Svalbard islands. Nearly 80 % of these were smaller than 0.01 km2 (1 ha), with the largest a few km2 in area. Lake distribution analysis identified six zones of increased lake density, five of which were located along the western coast of Spitsbergen. The FUI was thus demonstrated to be useful for the monitoring of Arctic lakes. The K-means clustering results and analysis of the spectral signatures divided the lakes into seven classes: clear water, moderately clear water, tundra, coastal tundra, meltwater, extreme meltwater, and supraglacial lakes. Meltwater and clear water lakes were the two most common types, accounting for about 80 % of the total lake area.

Temperature and spatial connectivity drive patterns in freshwater macroinvertebrate diversity across the Arctic

Abstract Warming in the Arctic is predicted to change freshwater biodiversity through loss of unique taxa and northward range expansion of lower latitude taxa. Detecting such changes requires establishing circumpolar baselines for diversity, and understanding the primary drivers of diversity. We examined benthic macroinvertebrate diversity using a circumpolar dataset of >1,500 Arctic lake and river sites. Rarefied α diversity within catchments was assessed along latitude and temperature gradients. Community composition was assessed through region‐scale analysis of β diversity and its components (nestedness and turnover), and analysis of biotic–abiotic relationships. Rarefied α diversity of lakes and rivers declined with increasing latitude, although more strongly across mainland regions than islands. Diversity was strongly related to air temperature, with the lowest diversity in the coldest catchments. Regional dissimilarity was highest when mainland regions were compared with islands, suggesting that connectivity limitations led to the strongest dissimilarity. High contributions of nestedness indicated that island regions contained a subset of the taxa found in mainland regions. High Arctic rivers and lakes were predominately occupied by Chironomidae and Oligochaeta, whereas Ephemeroptera, Plecoptera, and Trichoptera taxa were more abundant at lower latitudes. Community composition was strongly associated with temperature, although geology and precipitation were also important correlates. The strong association with temperature supports the prediction that warming will increase Arctic macroinvertebrate diversity, although low diversity on islands suggests that this increase will be limited by biogeographical constraints. Long‐term harmonised monitoring across the circumpolar region is necessary to detect such changes to diversity and inform science‐based management.

Specific Features of the Macrozoobenthic Communities of Small Arctic Lakes in Eurasia

The taxonomic structure, typology, species richness, and total abundance of bentic and littoral macroinvertebrate communities from small lakes of the Arctic and Subarctic zones are considered on the basis of original data from three northern Palearctic regions (the foot of the Putorana Plateau, Kolguev Island, and Western Svalbard Island). A comparative analysis of the communities of these regions has been carried out. The features of High Arctic insular, Low Arctic, subarctic, and boreal lake communities are discussed using a large volume of literature data. The complex pattern of changes in the total benthos biomass of small lakes has been revealed: it decreases in the subarctic taiga, increases in the hypoarctic tundra, and decreases again in the High Arctic.

Water column gradients beneath the summer ice of a High Arctic freshwater lake as indicators of sensitivity to climate change

Ice cover persists throughout summer over many lakes at extreme polar latitudes but is likely to become increasingly rare with ongoing climate change. Here we addressed the question of how summer ice-cover affects the underlying water column of Ward Hunt Lake, a freshwater lake in the Canadian High Arctic, with attention to its vertical gradients in limnological properties that would be disrupted by ice loss. Profiling in the deepest part of the lake under thick mid-summer ice revealed a high degree of vertical structure, with gradients in temperature, conductivity and dissolved gases. Dissolved oxygen, nitrous oxide, carbon dioxide and methane rose with depth to concentrations well above air-equilibrium, with oxygen values at > 150% saturation in a mid-water column layer of potential convective mixing. Fatty acid signatures of the seston also varied with depth. Benthic microbial mats were the dominant phototrophs, growing under a dim green light regime controlled by the ice cover, water itself and weakly colored dissolved organic matter that was mostly autochthonous in origin. In this and other polar lakes, future loss of mid-summer ice will completely change many water column properties and benthic light conditions, resulting in a markedly different ecosystem regime.

The Influence of Snow and Ice Albedo towards Improved Lake Ice Simulations

Lake ice models are a vital tool for studying the response of ice-covered lakes to changing climates throughout the world. The Canadian Lake Ice Model (CLIMo) is a one-dimensional freshwater ice cover model that simulates Arctic and sub-Arctic lake ice cover well. Modelling ice cover in temperate regions has presented challenges due to the differences in ice composition between northern and temperate region lake ice. This study presents a comparison of measured and modelled ice regimes, with a focus on refining CLIMo for temperate regions. The study sites include two temperate region lakes (MacDonald Lake and Clear Lake, Central Ontario) and two High Arctic lakes (Resolute Lake and Small Lake, Nunavut) where climate and ice cover information have been recorded over three seasons. The ice cover simulations were validated with a combination of time lapse imagery, field measurements of snow depth, snow density, ice thickness and albedo data, and historical ice records from the Canadian Ice Database (for Resolute Lake). Simulations of High Arctic lake ice cover show good agreement with previous studies for ice-on and ice-off dates (MAE 6 to 8 days). Unadjusted simulations for the temperate region lakes show good ice-on timing, but an under-representation of ice thickness, and earlier complete ice-off timing (~3 to 5 weeks). Field measurements were used to adjust the albedo values used in CLIMo, which resulted in improvements to both simulated ice thickness (~3 cm MAE compared to manual measurements), and ice-off timing, within 0 to 7 days (2 days MAE) of observations. These findings suggest regionally specific measurements of albedo can improve the accuracy of lake ice simulations, which further our knowledge of the response of temperate and High Arctic lake ice regimes to climate conditions.

Warming Climate Is Reducing the Diversity of Dominant Microbes in the Largest High Arctic Lake.

Temperatures in the Arctic are expected to increase dramatically over the next century, and transform high latitude watersheds. However, little is known about how microbial communities and their underlying metabolic processes will be affected by these environmental changes in freshwater sedimentary systems. To address this knowledge gap, we analyzed sediments from Lake Hazen, NU Canada. Here, we exploit the spatial heterogeneity created by varying runoff regimes across the watershed of this uniquely large high-latitude lake to test how a transition from low to high runoff, used as one proxy for climate change, affects the community structure and functional potential of dominant microbes. Based on metagenomic analyses of lake sediments along these spatial gradients, we show that increasing runoff leads to a decrease in taxonomic and functional diversity of sediment microbes. Our findings are likely to apply to other, smaller, glacierized watersheds typical of polar or high latitude ecosystems; we can predict that such changes will have far reaching consequences on these ecosystems by affecting nutrient biogeochemical cycling, the direction and magnitude of which are yet to be determined.