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At least 343 records · Page 19Linked to original sources
USGS2024

Sight and blindness: The relationship between ostracod eyes, water depth, and light availability in the Arctic Ocean

Eye loss has been a long-standing interest in evolutionary biology. Many organisms that inhabit environments without light penetration, for example the deep sea, exhibit eye loss and thus become blind. However, water-depth distribution of eyes in marine organisms is poorly understood. Ostracods are widely distributed crustaceans, and many sighted marine ostracods have eye tubercles (lenses) on their shells. Since eye tubercles are visible on the shells illustrated in much literature, it is easy to determine their presence or absence via a literature survey. Here, we used a large Arctic-wide ostracod census dataset (Arctic Ostracode Database) to calculate the eye index (the percentage of species with eyes), and compare them with water depth and light availability. As water depth increases, eye index values decrease and become constantly zero in water deeper than 1000 m. Similar decline of sighted species with increasing depth is also known in isopods and amphipods, suggesting that it may be common in other crustaceans and perhaps in deep-sea organisms in general. We also show that eye index values increase as light availability increases. This study is the first to quantify how distributions of sighted and blind species change with light availability, giving baseline information on vision in the deep sea.

Limnology and Oceanography↗
USGS2024

Arctic fishes reveal patterns in radiocarbon age across habitats and with recent climate change

Climate change alters the sources and age of carbon in Arctic food webs by fostering the release of older carbon from degrading permafrost. Radiocarbon ( 14 C) traces carbon sources and age, but data before rapid warming are rare and limit assessments over time. We capitalized on 14 C data collected ~ 40 years ago that used fish as natural samplers by resampling the same species today. Among resampled fish, those using freshwater food webs had the oldest 14 C ages (> 1000 yr BP), while those using marine food webs had the youngest 14 C ages (near modern). One migratory species encompassed the entire range of 14 C ages because juveniles fed in freshwater streams and adults fed in offshore marine habitats. Over ~ 40 yr, average 14 C ages of freshwater and marine feeding fish shifted closer to atmospheric values, suggesting a potential influence from “greening of the Arctic.”

Alaska↗
USGS2017

Human-polar bear interactions in a changing Arctic: Existing and emerging concerns

The behavior and sociality of polar bears ( Ursus maritimus ) have been shaped by evolved preferences for sea ice habitat and preying on marine mammals. However, human behavior is causing changes to the Arctic marine ecosystem through the influence of greenhouse gas emissions that drive long-term change in ecosystem processes and via the presence of in situ stressors associated with increasing human activities. These changes are making it more difficult for polar bears to reliably use their traditional habitats and maintain fitness. Here, we provide an overview of how human activities in the Arctic are likely to change a polar bear’s behavior and to influence their resilience to environmental change. Developing a more thorough understanding of polar bear behavior and their capacity for flexibility in response to anthropogenic disturbances and subsequent mitigations may lead to successful near-term management interventions.

Book chapter↗
USGS2017

Patterns and controls of mercury accumulation in sediments from three thermokarst lakes on the Arctic Coastal Plain of Alaska

The biogeochemical cycle of mercury will be influenced by climate change, particularly at higher latitudes. Investigations of historical mercury accumulation in lake sediments inform future predictions as to how climate change might affect mercury biogeochemistry; however, in regions with a paucity of data, such as the thermokarst-rich Arctic Coastal Plain of Alaska (ACP), the trajectory of mercury accumulation in lake sediments is particularly uncertain. Sediment cores from three thermokarst lakes on the ACP were analyzed to understand changes in, and drivers of, Hg accumulation over the past ~ 100 years. Mercury accumulation in two of the three lakes was variable and high over the past century (91.96 and 78.6 µg/m 2 /year), and largely controlled by sedimentation rate. Mercury accumulation in the third lake was lower (14.2 µg/m 2 /year), more temporally uniform, and was more strongly related to sediment Hg concentration than sedimentation rate. Sediment mercury concentrations were quantitatively related to measures of sediment composition and VRS-inferred chlorophyll a , and sedimentation rates were related to various catchment characteristics. These results were compared to data from 37 previously studied Arctic and Alaskan lakes. Results from the meta-analysis indicate that thermokarst lakes have significantly higher and more variable Hg accumulation rates than non-thermokarst lakes, suggesting that certain properties (e.g., thermal erosion, thaw slumping, low hydraulic conductivity) likely make lakes prone to high and variable Hg accumulation rates. Differences and high variability in Hg accumulation among high latitude lakes highlight the complexity of predicting future climate-related change impacts on mercury cycling in these environments.

Alaska↗
USGS2010

Two mechanisms of aquatic and terrestrial habitat change along an Alaskan Arctic coastline

Arctic habitats at the interface between land and sea are particularly vulnerable to climate change. The northern Teshekpuk Lake Special Area (N-TLSA), a coastal plain ecosystem along the Beaufort Sea in northern Alaska, provides habitat for migratory waterbirds, caribou, and potentially, denning polar bears. The 60-km coastline of N-TLSA is experiencing increasing rates of coastline erosion and storm surge flooding far inland resulting in lake drainage and conversion of freshwater lakes to estuaries. These physical mechanisms are affecting upland tundra as well. To better understand how these processes are affecting habitat, we analyzed long-term observational records coupled with recent short-term monitoring. Nearly the entire coastline has accelerating rates of erosion ranging from 6 m/year from 1955 to 1979 and most recently peaking at 17 m/year from 2007 to 2009, yet an intensive monitoring site along a higher bluff (3–6 masl) suggested high interannual variability. The frequency and magnitude of storm events appears to be increasing along this coastline and these patterns correspond to a greater number of lake tapping and flooding events since 2000. For the entire N-TLSA, we estimate that 6% of the landscape consists of salt-burned tundra, while 41% is prone to storm surge flooding. This offset may indicate the relative frequency of low-magnitude flood events along the coastal fringe. Monitoring of coastline lakes confirms that moderate westerly storms create extensive flooding, while easterly storms have negligible effects on lakes and low-lying tundra. This study of two interacting physical mechanisms, coastal erosion and storm surge flooding, provides an important example of the complexities and data needs for predicting habitat change and biological responses along Arctic land–ocean interfaces.

Alaska↗
USGS2012

Terrestrial and marine trophic pathways support young-of-year growth in a nearshore Arctic fish

River discharge supplies nearshore communities with a terrestrial carbon source that is often reflected in invertebrate and fish consumers. Recent studies in the Beaufort Sea have documented widespread terrestrial carbon use among invertebrates, but only limited use among nearshore fish consumers. Here, we examine the carbon source and diet of rapidly growing young-of-year Arctic cisco ( Coregonus autumnalis ) using stable isotope values (δ 13 C and δ 15 N) from muscle and diet analysis (stomach contents) during a critical and previously unsampled life stage. Stable isotope values (δ 15 N and δ 13 C) may differentiate between terrestrial and marine sources and integrate over longer time frames (weeks). Diet analysis provides species-specific information, but only from recent foraging (days). Average δ 13 C for all individuals was −25.7 ‰, with the smallest individuals possessing significantly depleted δ 13 C values indicative of a stronger reliance of terrestrial carbon sources as compared to larger individuals. Average δ 15 N for all individuals was 10.4 ‰, with little variation among individuals. As fish length increased, the proportion of offshore Calanus prey and neritic Mysis prey increased. Rapid young-of-year growth in Arctic cisco appears to use terrestrial carbon sources obtained by consuming a mixture of neritic and offshore zooplankton. Shifts in the magnitude or phenology of river discharge and the delivery of terrestrial carbon may alter the ecology of nearshore fish consumers.

Polar Biology↗
USGS2015

Diet of yellow-billed loons ( Gavia adamsii ) in Arctic lakes during the nesting season inferred from fatty acid analysis

Understanding the dietary habits of yellow-billed loons ( Gavia adamsii ) can give important insights into their ecology, however, studying the diet of loons is difficult when direct observation or specimen collection is impractical. We investigate the diet of yellow-billed loons nesting on the Arctic Coastal Plain of Alaska using quantitative fatty acid signature analysis. Tissue analysis from 26 yellow-billed loons and eleven prey groups (nine fish species and two invertebrate groups) from Arctic lakes suggests that yellow-billed loons are eating high proportions of Alaska blackfish ( Dallia pectoralis ), broad whitefish ( Coregonus nasus ) and three-spined stickleback ( Gasterosteus aculeatus ) during late spring and early summer. The prominence of blackfish in diets highlights the widespread availability of blackfish during the early stages of loon nesting, soon after spring thaw. The high proportions of broad whitefish and three-spined stickleback may reflect a residual signal from the coastal staging period prior to establishing nesting territories on lakes, when loons are more likely to encounter these species. Our analyses were sensitive to the choice of calibration coefficient based on data from three different species, indicating the need for development of loon-specific coefficients for future study and confirmation of our results. Regardless, fish that are coastally distributed and that successfully overwinter in lakes are likely key food items for yellow-billed loons early in the nesting season.

Alaska↗
USGS2020

Mitochondrial genome diversity and population mitogenomics of Polar cod (Boreogadus saida) and Arctic dwelling gadoids

High-latitude fish typically exhibit a narrow thermal tolerance window, which may pose challenges when coping with temperatures that shift outside of a species’ range of tolerance. Due to its role in aerobic metabolism and energy balance, the mitochondrial genome is likely critical for the acclimation and adaptation to differing temperature regimes in marine ectotherms. As oceans continue to warm, there is growing need to understand the ability of organisms to respond to changing environmental conditions given evidence that some species, in particular cold-water species, may already be experiencing difficulties. To assess how Arctic gadids in Alaska have responded to differential thermal preferences in the past and how regions are interconnected, we sequenced complete mitochondrial genomes for four Arctic gadids to determine the distribution of mitochondrial diversity and population-level structure as well as to detect signatures of selection acting on the mitochondrial genome. We found little population-level structure within all four species with the clear exception of Gulf of Alaska saffron cod ( Eleginus gracilis ). Northern localities exhibited higher levels of genetic diversity and primarily northern lineages were observed within polar cod ( Boreogadus saida ) and saffron cod, likely reflecting asymmetrical dispersal and potentially admixture of distinct lineages via ocean currents. The main evolutionary force shaping the evolution of the mitogenome appears to be purifying selection, but we also identified potential positive selection of candidate amino acid replacements primarily in complex I (ND genes) in polar cod. The high levels of mitochondrial diversity observed in our study and large population size may provide this species with the ability to respond evolutionarily (i.e. long-term) to a changing environment.

Alaska↗
USGS2024

Local environmental conditions structured discrete fish assemblages in Arctic lagoons

Rapid changes in sea ice extent and changes in freshwater inputs from land are rapidly changing the nature of Arctic estuarine ecosystems. In the Beaufort Sea, these nearshore habitats are known for their high productivity and mix of marine resident and diadromous fishes that have great subsistence value for Indigenous communities. There is, however, a lack of information on the spatial variation among Arctic nearshore fish communities as related to environmental drivers. In summers of 2017–2019, we sampled fishes in four estuarine ecosystems to assess community composition and relate fish abundance to temperature, salinity, and wind conditions. We found fish communities were heterogeneous over larger spatial extents with rivers forming fresh estuarine plumes that supported diadromous species (e.g., broad whitefish Coregonus nasus ), while lagoons with reduced freshwater input and higher salinities were associated with marine species (e.g., saffron cod Eleginus gracilis ). West–East directional winds accounted for up to 66% of the community variation, indicating importance of the wind-driven balance between fresh and marine water masses. Salinity and temperature accounted for up to 54% and 37% of the variation among lagoon communities, respectively. Recent sea ice declines provide more opportunity for wind to influence oceanographic conditions and biological communities. Current subsistence practices, future commercial fishing opportunities, and on-going oil and gas activities benefit from a better understanding of current fish community distributions. This work provides important data on fish spatial distributions and community composition, providing a basis for fish community response to changing climatic conditions and anthropogenic use.

Polar Biology↗
USGS2014

Understanding how lake populations of arctic char are structured and function with special consideration of the potential effects of climate change: A multi-faceted approach.

Size dimorphism in fish populations, both its causes and consequences, has been an area of considerable focus; however, uncertainty remains whether size dimorphism is dynamic or stabilizing and about the role of exogenous factors. Here, we explored patterns among empirical vital rates, population structure, abundance and trend, and predicted the effects of climate change on populations of arctic char ( Salvelinus alpinus) in two lakes. Both populations cycle dramatically between dominance by small (≤300 mm) and large (>300 mm) char. Apparent survival (Φ) and specific growth rates (SGR) were relatively high (40–96 %; SGR range 0.03–1.5 %) and comparable to those of conspecifics at lower latitudes. Climate change scenarios mimicked observed patterns of warming and resulted in temperatures closer to optimal for char growth (15.15 °C) and a longer growing season. An increase in consumption rates (28–34 %) under climate change scenarios led to much greater growth rates (23–34 %). Higher growth rates predicted under climate change resulted in an even greater predicted amplitude of cycles in population structure as well as an increase in reproductive output ( R o ) and decrease in generation time ( G o ). Collectively, these results indicate arctic char populations (not just individuals) are extremely sensitive to small changes in the number of ice-free days. We hypothesize years with a longer growing season, predicted to occur more often under climate change, produce elevated growth rates of small char and act in a manner similar to a “resource pulse,” allowing a sub-set of small char to “break through,” thus setting the cycle in population structure.

Oecologia↗
USGS2012

Uranium isotopes (234U/238U) in rivers of the Yukon Basin (Alaska and Canada) as an aid in identifying water sources, with implications for monitoring hydrologic change in arctic regions

The ability to detect hydrologic variation in large arctic river systems is of major importance in understanding and predicting effects of climate change in high-latitude environments. Monitoring uranium isotopes ( 234 U and 238 U) in river water of the Yukon River Basin of Alaska and northwestern Canada (2001–2005) has enhanced the ability to identify water sources to rivers, as well as detect flow changes that have occurred over the 5-year study. Uranium isotopic data for the Yukon River and major tributaries (the Porcupine and Tanana rivers) identify several sources that contribute to river flow, including: deep groundwater, seasonally frozen river-valley alluvium groundwater, and high-elevation glacial melt water. The main-stem Yukon River exhibits patterns of uranium isotopic variation at several locations that reflect input from ice melt and shallow groundwater in the spring, as well as a multi-year pattern of increased variability in timing and relative amount of water supplied from higher elevations within the basin. Results of this study demonstrate both the utility of uranium isotopes in revealing sources of water in large river systems and of incorporating uranium isotope analysis in long-term monitoring of arctic river systems that attempt to assess the effects of climate change.

Yukon Basin↗
USGS2019

Constraining dissolved organic matter sources and temporal variability in a model sub-Arctic lake

Circumpolar lakes comprise ~ 1.4 million km 2 of arctic and subarctic landscapes and are vulnerable to change in vegetation, permafrost distribution, and hydrological conditions in response to climate warming. However, the composition and cycling of dissolved organic matter (DOM) is poorly understood for these lakes because most are remote and unstudied. The goal of this study was to assess timescale and source controls on DOM composition in Canvasback Lake, a shallow, sub-Arctic lake in interior Alaska with similar hydrologic and geomorphic characteristics to about a quarter of circumpolar lake ecosystems. Lake dissolved organic carbon (DOC) concentration varied by as much as 16% from the mean (3.34 mg L −1 change) through diel cycles in spring 2016 to fall 2017 and was accompanied by minor changes in DOM composition. At the seasonal scale, DOC concentration increased from spring through fall to very high concentrations under ice in winter. Decreases in both condensed aromatic and polyphenolic compound classes and lignin carbon-normalized yield, plus increased relative abundance of aliphatic compounds, suggests that DOM composition shifts from a pulse of allochthonous DOM in the spring to more autochthonous under-ice. These changes highlight the seasonally-dynamic nature of DOM in circumpolar lakes that are poorly captured by single-visit lake surveys and underscores the need to measure DOM properties and fate consistently across multiple timescales (i.e. seasonally) to better constrain the role of DOM in lake processes. To further assess DOM sources, a suite of endmember leachates were compared to bulk lake DOM, indicating solely allochthonous inputs are not well reflected in lake DOM, highlighting the role of degradation processes or mixing with autochthonous sources. Thus, Canvasback Lake appears less well connected to terrestrial inputs compared to past studies of northern high-latitude lakes and does not behave as previous boreal lake models suggest.

Alaska↗
USGS2004

Is climate change affecting wolf populations in the high arctic?

Gobal climate change may affect wolves in Canada’s High Arctic (80° N) acting through three trophic levels (vegetation, herbivores, and wolves). A wolf pack dependent on muskoxen and arctic hares in the Eureka area of Ellesmere Island denned and produced pups most years from at least 1986 through 1997. However, when summer snow covered vegetation in 1997 and 2000 for the first time since records were kept, halving the herbivore nutrition-replenishment period, muskox and hare numbers dropped drastically, and the area stopped supporting denning wolves through 2003. The unusual weather triggering these events was consistent with global-climate-change phenomena.

Climatic Change↗
USGS2022

A landscape approach for identifying potential reestablishment sites for extirpated stream fishes: an example with Arctic grayling (Thymallus arcticus) in Michigan

Habitat degradation combined with climate change increases the threat of extinction for stream fishes. In response to these threats, efforts to reestablish species within formerly occupied streams or translocation to suitable areas may be effective conservation strategies. In the absence of historic species presence data, identifying locations where suitable habitat exists across many fluvial habitats may limit the effectiveness of reestablishments. We present an approach that ranks habitat for stream fish reestablishment over large areas using best available information. Using the locally extirpated Arctic grayling ( Thymallus arcticus ) in Michigan, USA as an example, we integrate information on species preferences and relationships between species with similar habitat requirements and landscape predictors of habitat to rank stream suitability. We find that unfragmented streams throughout the historical range of Arctic grayling and areas previously unoccupied by the species are potential locations for conservation action. However, we note that projected increases in summer water temperatures may reduce the amount of thermally suitable habitat in some top-ranked locations by up to 30%. Given its inherent flexibility in data requirements, our landscape-level approach may be a valuable tool that supports planning for species reestablishment.

Michigan↗
USGS2010

Aggregation methodology for the circum-arctic resource appraisal

This paper presents a methodology that intends to aggregate the results of a recent assessment of undiscovered conventional oil and gas resources of the Arctic by the U.S. Geological Survey. The assessment occurred in 48 geologically defined regions called assessment units. The methodology includes using assessor specified pair-wise correlations as the basis to construct a correlation matrix. Sampling from this matrix generates more realistic uncertainty estimates of aggregated resources than if assumptions of total independence or total dependence are made. The latter two assumptions result in overly narrow or overly broad estimates. Aggregation results for resources in regions north of the Arctic Circle are presented.

Mathematical Geosciences↗
USGS1978

Arctic continental shelf morphology related to sea-ice zonation, Beaufort Sea, Alaska

Landsat-1 and NOAA satellite imagery for the winter 1972–1973, and a variety of ice and sea-floor data were used to study sea-ice zonation and dynamics and their relation to bottom morphology and geology on the Beaufort Sea continental shelf of arctic Alaska. In early winter the location of the boundary between undeformed fast ice and westward-drifting pack ice of the Pacific Gyre is controlled by major coastal promontories. Pronounced linear pressure- and shear-ridges, as well as hummock fields, form along this boundary and are stabilized by grounding, generally between the 10- and 20-m isobaths. Slippage along this boundary occurs intermittently at or seaward of the grounded ridges, forming new grounded ridges in a widening zone, the stamukhi zone, which by late winter extends out to the 40-m isobath. Between intermittent events along the stamukhi zone, pack-ice drift and slippage is continuous along the shelf edge, at average rates of 3–10 km/day. Whether slippage occurs along the stamukhi zone or along the shelf edge, it is restricted to a zone several hundred meters wide, and ice seaward of the slip face moves at uniform rates without discernible drag effects. A causal relationship is seen between the spatial distribution of major ice-ridge systems and offshore shoals downdrift of major coastal promontories. The shoals appear to have migrated shoreward under the influence of ice up to 400 m in the last 25 years. The sea floor seaward of these shoals within the stamukhi zone shows high ice-gouge density, large incision depths, and a high degree of disruption of internal sedimentary structures. The concentration of large ice ridges and our sea floor data in the stamukhi zone indicate that much of the available marine energy is expended here, while the inner shelf and coast, where the relatively undeformed fast ice grows, are sheltered. There is evidence that anomalies in the overall arctic shelf profile are related to sea-ice zonation, ice dynamics, and bottom processes. A proposed ice zonation, including zones of (1) bottom-fast ice, (2) floating fast ice, (3) stamukhi, and (4) seasonal pack ice, emphasizes ice interaction with the shelf surface and differs from previous zonation. Certain aspects of the results reported here are directly applicable to planned offshore developments in the Prudhoe Bay oil field. Properly placed artificial structures similar to offshore shoals should be able to withstand the forces of the ice, serve to modify the observed ice zonation, and might be used to make the environment less hostile to human activities.

Alaska↗
USGS1987

Field observations of slush ice generated during freeze-up in arctic coastal waters

In some years, large volumes of slush ice charged with sediment are generated from frazil crystals in the shallow Beaufort Sea during strong storms at the time of freeze-up. Such events terminate the navigation season, and because of accompanying hostile conditions, little is known about the processes acting. The water-saturated slush ice, which may reach a thickness of 4 m, exists for only a few days before freezing from the surface downward arrests further wave motion or pancake ice forms. Movements of small vessels and divers in the slush ice occurs only in phase with passing waves, producing compression and rarefaction, and internal pressure pulses. Where in contact with the seafloor, the agitated slush ice moves cobble-size material, generates large sediment ripples, and may possibly produce a flat rampart observed on the arctic shoreface in some years. Processes charging the slush ice with as much as 1000 m 3 km −2 of sediment remain uncertain, but our field observations rule out previously proposed filtration from turbid waters as a likely mechanism. Sedimentary particles apparently are only trapped in the interstices of the slush ice rather than being held by adhesion, since wave-related internal pressure oscillations result in downward particle movement and cleansing of the slush ice. This loss of sediment explains the typical downward increase in sediment concentration in that part of the fast-ice canopy composed largely of frazil ice. The congealing slush ice in coastal water does not become fast ice until grounded ridges are formed in the stamukhi zone, one to two months after freeze-up begins. During this period of new-ice mobility, long-range sediment transport occurs. The sediment load held by the fast-ice canopy in the area between the Colville and Sagavanirktok River deltas in the winter of 1978–1979 was 16 times larger than the yearly river input to the same area. This sediment most likely was rafted from Canada, more than 400 km to the east, during a brief time period in the previous fall. Ocean turbulence is greatly reduced while the congealing slush ice drifts about. Therefore, new ice then forming in intervening open-water areas is clean. These events explain the patchy appearance of the fast ice after the summer snowmelt. More work on the important phenomena reported here is needed to close a major gap in the knowledge of the arctic marine environment.

Marine Geology↗
USGS2018

A transcriptome resource for the Arctic Cod (Boreogadus saida)

Arctic Cod ( Boreogadus saida ) serve as an important link in Arctic food webs and are thus considered an important species for environmental monitoring. RNA-Seq was conducted on samples from wild-collected individuals representing various age classes and tissue types to obtain as complete a transcriptome as possible on an Illumina MiSeq, which resulted in a total of 64,457 transcripts with an average length of 295 bp. We identified well-known genes that are associated with temperature change or response to pollutants. This RNA-Seq effort provides the first insight into the B. saida transcriptome, which can be a starting point for investigations identifying genes for local adaptation and genomic responses to future environmental change.

Marine Genomics↗