• Growth and nutritional development of reindeer (Rangifer tarandus) and muskoxen (Ovibos moschatus)

      Knott, Katrina K. (2004-08)
      Young ruminants must grow and develop digestive function during brief summers in the Arctic. I examined growth and development of nutritional organs in reindeer and muskoxen as neonates (1 d), during transition from milk to forage (30-60 d) and at maturity. Reindeer and muskoxen gave birth to relatively smaller offspring than ruminants from more temperate regions. Costs of small birth mass are likely offset in neonates by an increase of thyroid hormones to enhance thermogenesis and hepatic reserves that provide additional nutrients during early development. Body mass gains during the neonatal period (1-30 d) were associated with well-developed abomasa that allow young to utilize milk immediately after birth. Transition to forage coincided with mass gains of the rumen, small intestine and colon. Digestive morphology also was modified to facilitate fermentation of plants and enhance digestion and absorption of nutrients by 60 days of age. Digestive anatomy of young reindeer and muskoxen also indicated that feeding strategies of adults may be determined from birth. Growth of reindeer and muskoxen, therefore, is dependent upon an endogenous sequence of nutritional development that allow young to take advantage of concentrated milk after birth and time fermentative function to plant emergence at high latitudes. These advances permit young to meet requirements of growth and establish reserves before winter.
    • Growth of juvenile chinook salmon (Oncorhynchus tshawytscha) as an indicator of density-dependence in the Chena River

      Perry, Megan T. (2012-08)
      In management of Pacific salmon, it is often assumed that density-dependent factors, mediated by the physical environment during freshwater residency, regulate population size prior to smolting and outmigration. However, in years following low escapement, temperature may be setting the upper limit on growth of juvenile chinook salmon Oncorhynchus tshawytscha during the summer rearing period. Given the importance of juvenile salmon survival for the eventual adult population size, we require a greater understanding of how density-dependent and independent factors affect juvenile demography through time. In this study we tested the hypotheses that (1) juvenile chinook salmon in the Chena River are food limited, and (2) that freshwater growth of juvenile chinook salmon is positively related with marine survival. We tested the first hypotheses using an in-situ supplemental feeding experiment, and the second hypothesis by conducting a retrospective analysis on juvenile growth estimated using a bioenergetics model related to return per spawner estimates from a stock-recruit analysis. We did not find evidence of food limitation, nor evidence that marine survival is correlated with freshwater growth. However, we did find some evidence suggesting that growth during the freshwater rearing period may be limited by food availability following years when adult escapement is high.
    • Growth, Morphology And Energetics Of Bowhead Whales (Balaena Mysticetus)

      George, John Craighead (2009)
      This thesis describes investigations on bowhead whales (Balaena mysticetus) conducted over the past three decades, specifically on age, growth, morphology and energetics. The examined whales were harvested by Inupiat Eskimo whale hunters primarily in Barrow, Alaska. Bowheads are robust cetaceans reaching 19 m in length and inhabit the ice-covered waters of the circumpolar Arctic. They have the thickest blubber (? 35 cm) of any cetacean and the longest (>4 m) and most extensive baleen apparatus. Bowheads are ~4 m at birth and grow rapidly to ~8 m in their first year; they then experience a 2-3 year growth pause in both body length and mass. However the baleen continues to grow during this period. Sex differences are minimal but adult females tend to grow longer than males and males have larger pectoral limbs. Based on several lines of evidence, bowheads may routinely live to 150 years and thereby the longest-lived mammal. The recovery of 19 th century stone weapons from recently harvested whales confirms these age estimates. Age was estimated for 48 whales using the aspartic acid racemization technique, based on intrinsic changes of aspartic acid within the eye lens. The age at sexual maturity for bowheads occurs in the mid-20s. All harvested whales examined showed strong thermal gradients through their blubber (dermis and epidermis). A similar thermal gradient was evident through the muscle which is atypical of most terrestrial mammals. The deep body temperature averaged 33.8�C (SD=0.83, N = 28) which is lower than in other non-hibernating eutherian mammals. I did not see elevation of body temperatures in chased whales -- in fact these whales had slightly lower core temperatures. Resting metabolic rates for whales were estimated using a heat-loss technique. The thermal conductivity of the blubber for 5 whales averaged about 0.23 Wm-1K-1; similar to that of other whales and marine mammals. Heat flux rates varied highest to lowest as follows: palatal rete, flukes, tongue and lowest for the thorax and flippers. The resulting metabolic rates were much lower (~ 1/3) than predicted by the Kleiber regression. These investigations suggest that bowhead whales are unique among mammals in several respects such as: (a) following weaning they appear to lose weight over a period of 2-3 years and grow little in body length, (b) resting metabolic rates and body temperatures are lower than in other cetaceans. Their extensive blubber likely buffers bowheads against high variability in primary and secondary productivity in arctic seas.
    • Gyrfalcon Breeding Biology In Alaska

      Booms, Travis L.; Huettmann, Falk; McCracken, Kevin (2010)
      This dissertation addresses specific research needs identified by a panel of experts on Gyrfalcon biology and conservation convened on 3 September, 2003 at the Raptor Research Foundation Scientific Conference in Anchorage, Alaska. The first chapter is a significant update and revision of the 1994 Gyrfalcon Birds of North America (BNA) species account, using all published papers and available grey literature from 1994--2007 and personal expertise from over 3,000 hours of coordinated observations. The second chapter reports results from a spatially explicit model, based on the best available compiled data from Alaska, that predicted Gyrfalcon breeding distribution and population size across Alaska. The model predicted that 75% and 7% of the state had a relative index of nest occurrence of <20% and >60%, respectively. Areas of high predicted occurrence primarily occurred in northern and western Alaska. Using environmental variables, the model estimated the size of the breeding Gyrfalcon population in Alaska is 546 +/- 180 pairs. In Chapter 3, I used repeated aerial surveys to estimate detection probabilities of cliff-nesting raptors from fixed-wing aircrafts and helicopters. Detection probabilities ranged from 0.79--0.10 and varied by species, observer experience, and study area/aircraft type. Generally, Gyrfalcons had the highest detection probability, followed by Golden Eagles, Common Ravens, and Rough-legged Hawks, though the exact pattern varied by study area and survey platform. In the final chapter, I described for the first time in North America Gyrfalcon nest site fidelity, breeding dispersal, and natal dispersal using molted feathers as non-invasive genetic tags. Gyrfalcons were highly faithful to study areas (100% fidelity) and breeding territories (98% fidelity), but not to specific nest sites (22% fidelity). Breeding dispersal distance averaged 750 +/- 870 m, and was similar between sexes. Natal dispersal of three nestlings representing 2.5% recruitment varied from 0--254 km. Mean territory tenure was 2.8 +/- 1.4 yrs and displayed a bimodal distribution with peaks at 1 and 4 years. Mean annual turnover at one study site was 20%. Gyrfalcons in one study area exhibited low, but significant population differentiation from the other two study areas.
    • Habitat associations, distribution, and abundance of Smith's longspur (Calcarius pictus), an uncommon species of concern in the Brooks Range, Alaska

      Wild, Teri Corvus; Powell, Abby; Verbyla, Dave; Kendall, Steve (2013-12)
      Smith's Longspur (Calcarius pictus) is a species of conservation concern in the U.S. and Canada, yet few studies have been conducted on their breeding grounds in the Arctic, which are expected to undergo dramatic changes due to climate change. For effective conservation, we need information on breeding distribution and abundance; thus I conducted surveys for Smith's Longspur and habitat characteristics across a broad geographic range that included twelve sites within Alaska's Brooks Range, June 2003-2009. My main objectives were to (1) locate breeding populations (2) describe habitats at local and broader geographic scales, (3) develop a predictive distribution map based on habitat characteristics, and (4) estimate densities and abundance of Smith's Longspurs. Smith's Longspurs were detected at seven of twelve sites and were associated with mixed sedge and shrub habitats with high cover of moss and sedges. Across the Brooks Range, I predicted patchy occurrence in valleys and foothills in the north- and south-eastern mountains and in upland plateaus in the western mountains. Density estimates varied, ranging from 0 - 0.39 males/ha due to their patchy distribution within and among sites. I estimated abundance as ~30,000 males in the Brooks Range. My data provides a baseline for future monitoring of this little-known species.
    • Habitat selection and sightability of moose in Southeast Alaska

      Oehlers, Susan A. (2007-08)
      We examined the role of scale and sex in habitat selection by radiocollared Alaskan moose (Alces alces gigas) on the Yakutat forelands, Alaska, USA. We used conditional logistic regression to quantify differences in habitats selected between sexes and seasons at 3 different spatial scales (250, 500, and 1000 m), and multi-response permutation procedure (MRPP) to test for differences in spatial distribution between the sexes. Sexes selected for habitats similarly during the mating season, when sexes generally were aggregated, whereas sexes exhibited differential habitat selection during the non-mating season when sexes were segregated. Both sexes selected habitats at the 1000 m scale; models limited to 2 variables, however, demonstrated differences in scales selected by the sexes. There was a significant difference between male and female spatial distribution during all months (MRPP; P <0.0001), and distances between individuals were higher in females than in males, particularly during spring. We also developed a sightability model for moose with logistic regression, and used Distance Sampling to develop sightability correction factors (SCFs). Application of the sightability model and Distance Sampling to a sample data set of 600 moose yielded population estimates of 652-1124 (x̄= 755) and 858-1062 (x̄ = 954) moose, respectively.
    • Habitat selection by calving caribou of the Central Arctic Herd, 1980-95

      Wolfe, Scott Adrian (2000-12)
      Habitat selection by calving caribou (Rangifer tarandus granti) of the Central Arctic Herd, Alaska, was assessed in relation to distance from roads, vegetation type, relative plant biomass (NDVI; Normalized Difference Vegetation Index), accumulation of plant biomass during early lactation (NDVIrate), snow cover, and terrain ruggedness. From 183 calving sites of 96 radio collared- females, 1980-95, calving distribution was estimated in reference (no development) and treatment (oilfields present) zones east and west of the Sagavanirktok River, respectively. In the reference zone, caribou regularly selected wet-graminoid vegetation, above-median NDVIrate, and non-rugged terrain; concentrated calving remained in habitats with zonal average NDVI on 21 June (NDVI621). In the treatment zone, selection patterns were inconsistent; concentrated calving shifted inland to rugged terrainwith low NDVI621 and away from development. Repeated use of lower-quality habitats in the treatment zone could compromise nutrient intake by calving females, thereby depressing reproductive success of the western-segment of the herd.
    • Headwater stream invertebrate communities: a comparison across ecoregions and logging histories

      Medhurst, R. Bruce (2007-08)
      Monitoring stream condition is not always conducted with understanding how climate may influence anthropogenic disturbances. Stream monitoring has traditionally been accomplished through sampling benthic invertebrates, while sampling drifting invertebrates as a potential monitoring tool has received little attention, in spite of drift often being easier and less expensive to sample. The objectives of this study were to understand how logging influences headwater stream invertebrate communities (benthic and drift) across two ecoregions in the Cascade Range, central Washington, and to determine whether drift samples might serve as a replacement for benthic samples in assessing headwater stream condition. Benthic and drifting invertebrates were sampled from 24 headwater streams in logged and unlogged watersheds within two ecoregions (wet and dry), and community metrics contrasted. Invertebrate community responses to logging varied with ecoregion (e.g., higher shredder densities in logged watersheds of wet ecoregion only). Differences in benthic community structure were not reflected in the drift, and relationships between benthos and drift were highly variable. Although both sampling types (benthic, drift) revealed ecoregional and land-use (logging) differences in invertebrate communities, lack of consistent relationships between the sampling types suggests drift sampling does not provide more reliable information about stream benthos or headwater stream condition.
    • Health Assessment In The Bowhead Whale

      Rosa, Cheryl; Blake, John E. (2006)
      Tissue samples and morphometric data were collected from 64 bowhead whales landed during the 1998-2002 subsistence hunts in Barrow and Kaktovik, Alaska. Our primary goal was to assess the health status of the Bering-Chukchi-Beaufort Seas stock of bowhead whales. Ages of whales were determined via aspartic acid racemization of the eye lens nucleus, baleen stable carbon isotope analysis and morphometric and histologic indices. We investigated the gross and microscopic anatomy of organs and blubber, thyroid hormone concentrations, serum haptoglobin, vitamin A and E concentrations in liver, blubber and serum and essential element concentrations in liver and kidney. Thyroid hormone and vitamin A were also evaluated as potential biomarkers of organochlorine (OC) concentrations in blubber, liver and serum. Neither of these substances was found to correlate with the relatively low OC concentrations found in these mysticetes. Histological changes of interest included renal interstitial fibrosis, hepatic periportal fibrosis/pigmentation/lipidosis, splenic extramedullary hematopoiesis and pulmonary fibromuscular hyperplasia. Changes in the kidney and lung were related to both age and renal and hepatic Cd concentrations. Most of the histological differences observed did not appear to adversely affect organ function or health of the individual. Thyroid hormone concentrations were stable over age/sex/seasonal groups, however, pregnant females had significantly lower total and free thyroxine than non-pregnant adult females and other age-sex classes. Serum haptoglobin was measured as an indirect determinant of acute inflammation, with three reactors found among 51 whales examined. Liver contained the highest mean concentrations of vitamins A and E (followed by epidermis, blubber, and serum and serum, epidermis, and blubber, in order). Finally, blubber percent collagen was measured at 30 locations on each whale and was found to be stable by site and most depths, with the most internal region of the reticular dermis being the only exception. Overall, the bowhead whales were healthy. However, climate change, offshore development and increases in arctic pollution emphasize the importance of baseline data collection. An ongoing surveillance effort is recommended to ensure that the species will be viable for generations to come and to assure subsistence users of the robust and healthy status of this stock of whales.
    • Heat Increment And Methane Production By Muskoxen Fed Browse

      Lawler, James Patrick; White, Robert G. (2001)
      Many browse species contain anti-herbivory compounds that deter consumers by their toxicity or digestive inhibitory effects. Animals that consume browse are assumed to pay a detoxification energy cost, which increases the heat increment of feeding (HIF). Ruminants also lose potentially metabolizable energy as methane (CH4); but browse may lower CH4 production. I hypothesized that increases in energy loss to HIF by animals eating browse could be offset by a reduction in energy lost via CH4 production. Muskoxen eat both graminoids and browse and are considered to be energetically conservative due to their existence in a sparse arctic environment. These traits make them ideal for energetic studies. Muskoxen were fasted for 24 h and then fed a test meal composed of hay mixed with graded percentages of one of three browse species (Willow: S. alaxensis, S. pulchra, birch: Betula nana). Browse consisted of twigs in winter and leaves in the summer. Heat increment of feeding and CH4 production were estimated with an indirect calorimeter. Muskoxen had a 33% lower metabolic rate in winter in comparison to summer. The main increase in EE from winter to summer occurred between April and May, and the summer to winter decrease between August and September. Addition of woody twigs or leaves of birch to hay diets tended to depress HIF following the test meal. Woody twigs and leaves of willow added to hay diets tended to increase HIF. Woody browse tended to lower CH4 production when fed at >20% of the meal. Leafy browse had variable effects on CH4 production; S. alaxensis was stimulatory, S. pulchra was inhibitory, while B. nana showed not consistent pattern. Generally, CH 4 production by muskoxen was low at 2.0--3.2% of GE intake when compared with estimates for sheep and cattle (2--12% of GE intake). Although diets high in fermentable carbohydrates stimulated methane production, secondary compounds apparently had a suppressing effect as deduced from the relation of in vitro digestibility to methane production. Given the low overall CH4 production in muskoxen, and the inconsistency of the relationship of CH4 to HIF, it is unlikely that significant gains in energy retention are made by reductions in CH4 production through browse consumption.
    • Heavy metal tissue distributions in southwestern Alaskan waterfowl: total mercury assays from muscle, brain, and bone

      Rothschild, Roger F. N. (2005-08)
      Food containing mercury has been identified as a possible health risk. Total mercury (THg), which is inorganic (Hg²), and methylmercury (MeHg) species, has been found in the arctic food web. In Alaska, birds are an important seasonal component of the diet, but have not been studied extensively and characterized for the presence of mercury. Birds are good subjects for examination because they feed at different trophic levels, can be long-lived, and are both abundant and widely distributed. Not only can birds monitor local Alaskan food webs, but, if they are migratory, can be used to compare exposure in different regions. Mercury levels in muscle, brain, and bone tissue of 140 birds taken by subsistence hunters across southwestern Alaska were determined. I tested the null hypothesis of no interspecific differences in total mercury levels in the 18 species of Alaska birds surveyed. There were interspecific differences with the Lesser Scaup (Aythyra marila mariloides), and the Black Scoter (Melanita nigra Americana), having the highest levels of mercury. In general, mercury levels were higher in muscle than in brain or bone. The mean values for mercury in the species studied were lower than the levels known to cause adverse reproductive or behavioral effects.
    • Hepatitis B in Arctic ground squirrels (Spermophylus parryi): epidemiology and population biology

      Joy, Philip John (2001-05)
      Using a mark-recapture design, an epidemiological investigation of Hepatitis B was performed on four colonies of Spermophylus parryi. Animals were trapped, marked and bled. Serum samples were screened for Hepatitis B markers. Program MARK was used to estimate survival rates. Prevalence rates ranged over 55% and 1999 rates were 10% higher than 1998. Vertical transmission of the virus was not observed and juveniles were unaffected by the mother's hepatitis status. Immigrants had lower prevalence rates than residents and incidence rates accelerated throughout the study. Survival was highest during the over-winter period and adult rates were lower in 1999. Recovered animals had different survival rates than other animals and survival rates of recovered animals were lower in 1999. Evidence suggests that delayed development of disease and/or environmental conditions lowered survival rates of recovered adults in 1999. Techniques that integrated epidemiology and population biology proved fruitful and worthy of further development.
    • Herbivore-mediated effects on ecosystem processes in a near-Arctic salt marsh

      Person, Brian Thomas (2001-12)
      Herbivores influence, and often regulate energy flow. I investigated interactions between herbivory and the foods on which geese rely while nesting and rearing their broods on the Yukon-Kuskokwim Delta in southwestern Alaska. In a captive Cackling Canada gosling (Branta Canadensis minima) experiment I decoupled the effects of seasonal declines in forage quality and availability on gosling development. An 11% decline in forage quality translated to goslings that were structurally smaller and 100 g lighter at 31 days of age. Forage availability had similar effects on gosling size, and the combined magnitude of these effects are similar to those observed in wild populations. I manipulated within-season grazing history of 'Carex subspathacea' swards within brood-rearing areas used by Black Brant geese (Branta bernicla nigricans). Spatial variation in forage quality and availability exceeded seasonal variation. Brant consumed over 95% of the annual aboveground production of these swards without any short- or apparent long-term effects on aboveground growth. Adding grazing pressure to 'C. ramenskii, ' or removing grazing pressure from 'C. subspathacea, ' resulted in a bi-directional shift in the morphology and nutritional characteristics of these sedges. The areal extent of 'C. subspathacea' increased 2 to 8% of the Tutakoke landscape with a concomitant decrease in 'C. ramenskii' meadows between 1991-1998. Brant have been increasing the carrying capacity of the Tutakoke River colony following a population decline in the early 1980's. The population has increased beginning in 1988, yet remains below historic numbers. Density-dependent effects on gosling growth accompanied the population increase initially. However, gosling mass has increased over the past decade due to herbivore-mediated increases in the areal extent of grazing lawns.
    • High frequency backscatter from the polar and auroral e-region ionosphere

      Forsythe, Victoriya V.; Bristow, William; Conde, Mark; Sahr, John; Zhang, Hui (2017-05)
      The Earth's ionosphere contains collisional and partially-ionized plasma. The electric field, produced by the interaction between the Earth's magnetosphere and the solar wind, drives the plasma bulk motion, also known as convection, in the F-region of the ionosphere. It can also destabilize the plasma in the E-region, producing irregularities or waves. Intermediatescale waves with wavelengths of hundreds of meters can cause scintillation and fading of the Global Navigation Satellite System (GNSS) signals, whereas the small-scale waves (< 100 m) can scatter radar signals, making possible detection of these plasma structures and measurements of their characteristics such as their phase velocity and intensity. In this work, production of the decameter-scale (10 m) irregularities in the ionospheric E-region (100-120 km in altitude) at high latitudes is investigated both theoretically, using linear fluid theory of plasma instability processes that generate small-scale plasma waves, and experimentally, by analyzing data collected with the newly-deployed high-southern-latitude radars within the Super Dual Auroral Radar Network (SuperDARN). The theoretical part of this work focuses on symmetry properties of the general dispersion relation that describes wave propagation in the collisional plasma in the two-stream and gradient-drift instability regimes. The instability growth rate and phase velocity are examined under the presence of a background parallel electric field, whose influence is demonstrated to break the spatial symmetry of the wave propagation patterns. In the observational part of this thesis, a novel dual radar setup is used to examine E-region irregularities in the magnetic polar cap by probing the E-region along the same line from opposite directions. The phase velocity analysis together with raytracing simulations demonstrated that, in the polar cap, the radar backscatter is primarily controlled by the plasma density conditions. In particular, when the E-region layer is strong and stratified, the radar backscatter properties are controlled by the convection velocity, whereas for a tilted E-layer, the height and aspect angle conditions are more important. Finally, the fundamental dependence of the E-region irregularity phase velocity on the component of the plasma convection is investigated using two new SuperDARN radars at high southern latitudes where plasma convection estimates are accurately deduced from all SuperDARN radars in the southern hemisphere. Statistical analysis is presented showing that the predominance of the E-region echoes of a particular polarity is strongly dictated by the orientation of the convection plasma ow which itself has a significant asymmetry towards westward zonal flow.
    • High resolution sequence stratigraphy and geochemistry of middle and upper Triassic sedimentary rocks, northeast and central Brooks Range, Alaska

      Kelly, Landon Neal (2004-08)
      Triassic age rocks constitute an important sedimentary interval on the North Slope of Alaska, because they include organic-rich source rocks that generated much of the oil that accumulated in the Prudhoe Bay field. Three detailed measured sections in the northeast and north-central Brooks Range are characterized using sequence stratigraphy, chemostratigraphy, biostratigraphy and ichnofabric, allowing interpretations about the evolution of the depositional environment and general paleogeographic setting through the Middle and Upper Triassic. High resolution correlation provides insight into the timing and pattern of source rock accumulation in the Shublik and Otuk Formations. Sequence and chemo-stratigraphic analyses suggest that deposition took place on a broad, low-angle shelf under fluctuating paleoceanographic conditions. Recorded are three third order sequences, each containing a sea level rise and highstand. Glauconitic, phosphatic, and organic-rich rocks of the Shublik and Otuk Formations indicate deposition in an environment characterized by oceanic upwelling. Organic and inorganic geochemical data support interpretations concerning paleoxygenation gradients. The cerium anomaly, manganese, phosphorus, vanadium, total organic carbon, and calcium-manganese ratio indicate dominantly oxic bottom waters during the Middle Triassic, dominantly low oxygen or anoxic conditions during much of the Upper Triassic, and a return to more oxic conditions in the late Upper Triassic.
    • High-Resolution Paleoceanography Of The Gulf Of Alaska, Subarctic Northeast Pacific Ocean, Since The Last Glacial Maximum: Insights Into A Dynamic Atmosphere-Ocean-Ecosystem Linkage At Decadal To Millennial Timescales

      Addison, Jason A.; Beget, James E.; Finney, Bruce P.; Bigelow, Nancy H.; Naidu, A. Sathy; Stockwell, Dean A.; Wooller, Matthew J. (2009)
      Environmental conditions in the Subarctic Northeast Pacific Ocean are an important component of North American climate patterns, as well as a potential driver of Northern Hemisphere climate variability. The North Pacific Ocean is also the terminus of modern global thermohaline circulation, suggesting that paleoceanographic records from this region have the potential to preserve evidence of both climate forcing and response on regional and global scales. A suite of high-resolution marine sediment cores collected from the Gulf of Alaska margin in 2004 provide new paleoceanographic records at decadal and centennial timescales from fjord and continental slope environments. Key findings include: (i) decadal oscillations in marine productivity correlate with previously identified terrestrial records, indicative of forcing by the Aleutian Low pressure cell; (ii) the standard binary model of the modern Pacific Decadal Oscillation (PDO) as the major pattern of ocean-atmosphere variability is insufficient to describe the full range of Holocene paleoenvironmental fluctuations observed in Gulf of Alaska records of marine productivity, freshwater discharge, and bottom-water anoxia; (iii) the North Pacific ecosystem is a sensitive recorder of abrupt climate events observed in global records; and (iv) the fjords of Southeast Alaska contain a detailed record of volcanic activity and fallout events useful for developing composite chronological models of sedimentation that correlate with other regionally important stratigraphic records. Collectively, the results presented here will potentially redefine current theoretical models of atmosphere-ocean-ecosystem variability in the North Pacific Ocean, as well as contribute to a growing body of high-resolution paleoenvironmental time-series datasets from the high latitudes.
    • Histone H2A-S122 is required for nuclear and mitochondrial genome stability

      Uffenbeck, Shannon R.; Krebs, Jocelyn; Kuhn, Thomas; Ii, Miki; O'Brien, Kristin (2013-08)
      Organization and maintenance of the mitochondrial and nuclear genomes are vastly different, yet I have shown that a single serine in the H2A C-terminal tail (H2A-S122) is critical for stability of both genomes in the budding yeast, Saccharomyces cerevisiae. Phosphorylation of H2A-S 122 has previously been implicated in the spindle assembly checkpoint (SAC), however I show that by mutating the serine to an alanine (H2A-S122A), the resulting aneuploidy occurs at a much higher rate than is observed by deleting its immediate downstream kinase BUB1. Furthermore, the H2A-S122A mutant displays an increased susceptibility to DNA damaging agents that is not observed in bubΔ1 deletion cells. Our studies also implicate H2A-S122 as critical to the maintenance of the mitochondrial genome, as upon introduction of the H2A-S122A mutation, cells rapidly lose their mitochondrial genomes.
    • History of the Chukchi borderland and the Amerasia basin, Arctic Ocean

      Ilhan, Ibrahim; Coakley, Bernard J.; Johnson, Christopher A.; Houseknecht, David W.; Whalen, Michael T. (2018-08)
      Structural and stratigraphic interpretation of 2D multi-channel seismic (MCS) reflection profiles through recognition of the sub-surface reflection patterns and integration of the seismic interpretation with the other geophysical and geological data reveal the history of the Chukchi Borderland. This investigation provides new constraints for the tectonic development of the Amerasia Basin. North-striking normal faults of the Chukchi Borderland dissect the continental basement into the Chukchi Plateau, Northwind Basin and Northwind Ridge from west to east. A well-developed angular unconformity (Au) separates the stratigraphic section into sub and super-Au seismic units. Sub-Au units include: (1) seaward dipping reflections (SDRs) observed in the juncture between the North Chukchi-Toll Basins and Chukchi Plateau; (2) growth and folded strata in the Northwind Basin; (3) thrust faults in the Northwind Basin and over the Northwind Ridge; and (4) a clinoform sequence that downlaps onto the extended continental crust of the Canada Basin, supported by presence of SDRs and diapiric reflections within the crust. Au is inferred to correlate to the Hauterivian (LCu) and the Middle Jurassic (Ju) unconformities of the Alaska North Slope. The SDRs indicate that the southwestern margin of the Chukchi Borderland may be a rifted continental margin. Loosely constrained age control of a super-Au unit (inferred condensed section, perhaps correlative to Hauterivian pebble shale or the Jurassic upper Kingak shale units of Alaska North Slope) implies that the rifted margin subsided no later than the earliest Cretaceous, providing a plausible time constraint for Middle Jurassic-earliest Cretaceous rifting in the North Chukchi Basin. The growth strata and north-striking normal faults of the Northwind Basin are continuous with the extensional structures of the Mississippian Hanna Trough, providing a geologic linkage between the two. The folding and thrust faults reveal a phase of contraction confined to sub-Au units of the south and eastern Northwind Basin and Northwind Ridge. The clinoform sequence of the Northwind Ridge-Canada Basin is inferred to correlate with the Upper Jurassic-Lower Cretaceous Kingak shale unit of Alaska North Slope, implying that the extension of the crust beneath the western Canada Basin occurred no later than the Middle Jurassic. Super-Au strata (~16 km) onlap the condensed section, SDRs, growth and passive margin strata from west to east, tapering down to a few kilometers north and eastward across the seismic grid. These are part of the Aptian through Cenozoic Brookian megasequence, a series of clinothems, deposited across the foreland of the Chukotka and Brooks Range orogens. These strata were deposited by northward-migrating depositional systems that progressively filled the North Chukchi Basin and buried the southern flank of the Chukchi Borderland, and deposited along the Northwind margin of the Canada Basin. Another unit of growth strata is observed in the Northwind Basin, indicating another phase of extension of the Boderland. The Upper Cretaceous section of the Brookian megasequence is displaced by normal faults over the Chukchi Plateau and inferred age-equivalent strata over the Northwind Ridge. These constrain the second phase of extension of the interior Borderland to the Late Cretaceous to Paleocene. The recognition of the sub-Au units and continuity of the super-Au units across the area, north-striking normal faults, and the absence of east-directed thrust faults between the Northwind Ridge and Canada Basin invalidate one model proposed for tectonic development of the Amerasia Basin. Models that require significant relative motion between the Chukchi Shelf and Borderland since the Middle Jurassic are precluded by these observations.
    • Home range, habitat selection, and movements of lynx (Lynx canadensis) in eastern interior Alaska

      Perham, Craig J.; Follmann, Erich H.; Rextad, Eric A.; Cook, Joseph; Jenkins, K. (1995-12)
      Lynx home ranges, habitat selection, and daily track deposition rates were determined in interior Alaska. Male home ranges averaged 167 km2 in 1991-92 and 127 km2 in 1992-93, but varied (14-270 km2); females averaged 33 km2 in 1991-92 and 48 km2 in 1992-93. Nomadic lynx displayed erratic movements and large ranges, whereas others dispersed from the study area. Lynx with small home ranges may use snowshoe hare refugia whereas other lynx may range over expanded areas to acquire food. Lynx preferred broadleaf and mixed forests and avoided dwarf shrub/tundra. Lynx used a 1959 burn more than expected; more recent burns (<11 years) were used less than expected. Track deposition was significantly related to snowfall, temperature and barometric pressure change (P< 0.001), the overall model, however, explained only 16% of the variation in deposition (R2 = 0.162). Temperature was most related to track deposition; as temperature increased, track deposition became more variable.
    • Hormonal regulation of alternative reproductive strategies

      Morgan, Tawna (2010-05)
      Variation in reproductive behavior permits individuals to optimize fitness given their genetics, physiological condition, social status, age and current environmental conditions. For species with alternative reproductive strategies, behavioral differences are driven by natural and sexual selection and further mediated by the endocrine system. In this study, I explore endocrinological mechanisms associated with alternative reproductive strategies in the ruff (Philomachus pugnax). Ruffs breed on leks, where males use one of three genetically determined alternative reproductive strategies or phenotypes. Resident males rely on male-male aggression, colorful plumage, large body size and intensive display activity to establish courts on a lek and attract females. Satellite males operate outside the dominance hierarchy of the lek, relying on semi-cooperative displays with residents, lighter display plumage coloration and agility to access receptive females. Males using the third male strategy, considered 'sneakers' or 'female mimics', completely forgo typical male breeding plumage, territoriality and obvious display behaviors to obtain clandestine access to females. The differences in level of aggression and display behaviors among phenotypes suggest predictable differences in steroid hormone concentrations, which play a critical role in breeding behavior in birds. I therefore examined seasonal hormone profiles of male ruffs and applied predictions from the challenge hypothesis, which posits circulating androgen concentration will vary in relation to intensity of male-male competition during the breeding season. Consistent with the challenge hypothesis, androgen levels were higher during periods of lek instability in territorial resident ruffs. In contrast, when housed in large flocks, androstenedione was elevated during the breeding season in satellite ruffs and followed the pattern typically observed for testosterone in polygamous birds. In response to distinctly different seasonal androgen and androstenedione profiles, I further examined the activational role of androstenedione on satellite male breeding behavior. Androstenedione stimulated both resident and satellite typical behaviors consistent with genetic morph, and thus did not specifically activate the satellite phenotype.