• Carbon exchange and permafrost collapse: implications for a changing climate

      Myers-Smith, Isla Heather (2005-05)
      With a warmer climate, the wetlands of Interior Alaska may experience more frequent or extensive stand-replacing fires and permafrost degradation. This, in turn may change the primary factors controlling carbon emissions. I measured carbon exchange along a moisture transect from the center of a sphagnum-dominated bog into a burned forest (2001 Survey Line Fire) on the Tanana River Floodplain. Both the bog and the surrounding burn were sinks for CO₂, and the bog was a CH₄ source in the abnormally dry summer of 2004. Thermokarst and subsiding soils were observed on the margin of the bog in the three years since the fire, increasing the anaerobic portion of the soil landscape. I observed the greatest variation in carbon fluxes in this portion of the transect. I conclude that permafrost collapse is altering the pattern of emissions from this landscape. I tracked historical changes in vegetation, hydrology and fire at this site through macrofossil, charcoal and diatom analysis of peat cores. The paleoecological record suggests that fire mediates permafrost collapse in this system. This study indicates that future changes in temperature and precipitation will alter carbon cycling and vegetation patterns across this boreal landscape.
    • Carbon flux and particle-associated microbial remineralization rates in the northern Bering and southern Chukchi seas

      O'Daly, Stephanie Hicks; McDonnell, Andrew M. P.; Hardy, Sarah M.; Johnson, Mark A. (2019-12)
      It has been hypothesized that climate change will reduce the strength and episodic nature of vernal phytoplankton blooms, increase heterotrophy of microbes and zooplankton, and weaken the tight coupling between pelagic and benthic production that is characteristic of Arctic continental shelves. As a part of the Arctic Shelf Growth, Advection, Respiration, and Deposition rates measurement (ASGARD) project, I quantified sinking particle fluxes and incubated sinking particles to measure the rate of microbial respiration associated with those particles. These measurements were used to characterize the strength of the pelagic-benthic connection. After a record-breaking year of warm temperatures and low-ice conditions in the northern Bering and southern Chukchi Seas, we observed massive vernal fluxes of sinking particulate organic carbon, ranking amongst the highest observed in the global oceans. Moreover, low rates of particle-associated microbial respiration indicate negligible recycling of sinking organic matter within the water column. These results suggest that the strength of the biological carbon pump may be maintained or enhanced in a warming Arctic, supporting strong benthic and upper trophic level productivity and carbon export.
    • Carbon isotopic composition of polycyclic aromatic hydrocarbons and their weathering in Kachemak Bay sediment

      Borland, Tara Ann (2004-05)
      Identification of sources of polycyclic aromatic hydrocarbons (PAH) in sediments is an important step in reducing anthropogenic contamination. Identifications based solely on the composition of PAH can be confounded by compositional changes during weathering and biodegradation. Stable isotopic composition of individual PAH offer a source marker that may be less susceptible to alteration. The [alpha]¹³C values of PAH in major potential sources to the Kachemak Bay area were analyzed. To determine the stability of the [alpha]¹³C values of PAH in crude and diesel oil, microbial degradation experiments using sediment from the Kachemak Bay, Alaska, area were conducted over a one-year period. The impact of weathering on the isotopic composition of North Slope crude oil and diesel oil was also examined over a five-week period in aquaria with Macoma balthica, an intertidal bivalve. For both degradation experiments, PAH concentrations decreased and their composition changed, but the [alpha]¹³C values of individual PAHs remained stable. Hence, [alpha]¹³C values of individual PAHs have excellent potential as a relatively stable indicator of their sources. Based on isotopic and compositional data, the PAH in Kachemak Bay sediments appear to have several sources.
    • Carbon Sequestration In Alaska's Boreal Forest: Planning For Resilience In A Changing Landscape

      Fresco, Nancy; Chapin, Stuart (2006)
      Northern ecosystems and those who rely upon them are facing a time of unprecedented rapid change. Global boreal forests will play an important role in the feedback loop between climate, ecosystems, and society. In this thesis, I examine forest carbon dynamics and the potential for carbon management in Interior boreal Alaska in three distinct frameworks, then analyze my results in the context of social-ecological resilience. In Chapter 1, I analyze comparative historical trends and current regulatory frameworks governing the use and management of boreal forests in Russia, Sweden, Canada, and Alaska, and assess indicators of socio-ecological sustainability in these regions. I conclude that low population density, limited fire suppression, and restricted economic expansion in Interior Alaska have resulted in a 21st-century landscape with less compromised human-ecosystem interactions than other regions. Relative wealth and a strong regulatory framework put Alaska in a position to manage for long-term objectives such as carbon sequestration. In Chapter 2, I model the landscape-level ecological possibilities for sequestration under three different climate scenarios and associated changes in fire and forest growth. My results indicate that Interior Alaska could act as either a weak carbon source or as a weak sink in the next hundred years, and that management for carbon credits via fire suppression would be inadvisable, given the associated uncertainty and risks. In Chapter 3, I perform a social, ecological, and economic analysis of the feasibility of switching from fossil fuels to wood energy in Interior Alaska villages. I demonstrate that this is a viable option with the potential benefits of providing lower-cost power, creating local employment, reducing the risk of catastrophic wildfire near human habitation, and earning marketable carbon credits. Finally, in Chapter 4, I assess how each of the above factors may impact social-ecological resilience. My results show some system characteristics that tend to bolster resilience and others that tend to increase vulnerability. I argue that in order to reduce vulnerability, management goals for Alaska's boreal forest must be long-term, flexible, cooperative, and locally integrated.
    • Carbon sources and trophic connectivity in seafloor food webs in the Alaska Arctic and sub-Arctic

      Oxtoby, Laura Elizabeth; Wooller, Matthew; O'Brien, Diane; Iken, Katrin; Horstmann, Larissa; Budge, Suzanne (2016-05)
      Stable isotope analysis offers critical insight into organic matter pathways that sustain and link consumers in a food web. Indirect examination of organic matter sources and consumer diets using stable isotope analysis is especially valuable in the Alaska Arctic and sub-Arctic marine realm, where organisms of interest are difficult to observe given their remote habitat and elusive behavior. The research objective of this body of work was to use novel applications of stable isotope analysis to extend our understanding of organic matter sources, trophic pathways, and resource competition among benthic consumers. Microphytobenthos, a community of photosynthesizing unicellular microscopic algal cells on the seafloor sediment, has not been included in stable isotope food web models in the Alaska Arctic and sub-Arctic due to challenges associated with sample collection and analysis. I constrained the isotopic composition of this potential algal source by integrating field measurements, physiological relationships previously established by laboratory studies, and a range of algal growth rates specific to high latitude primary production. Relative to other sources of primary production in the Arctic, sub-Arctic, and lower latitude ecosystems, estimates for stable carbon isotope values of total organic carbon from microphytobenthos in the Beaufort and Chukchi seas were higher than those for Arctic riverine organic matter, but lower than ice algal sources and microphytobenthos measurements from lower latitudes. To further elucidate trophic pathways and resource partitioning among benthic invertebrate consumers, I combined compound-specific stable isotope analysis, a relatively new analytical tool, with fatty acid analysis to estimate proportional contributions of algal sources from ice, open ocean, and surface sediments to common polychaete and bivalve consumers in the Bering Sea. Benthic invertebrates were collected in 2009-2010 and represented a diverse range of feeding strategies, including the suspension/surface deposit-feeding bivalves Macoma calcarea and Ennucula tenuis, the subsurface deposit-feeding bivalve, Nuculana radiata, the head down deposit-feeding polychaete Leitoscoloplos pugettensis, and the predator/scavenger Nephtys spp. Differences in dominant algal sources to these invertebrate consumers corresponded, for the most part, to feeding strategy. Bivalves primarily obtained fatty acids from surface sediments, whereas L. pugettensis obtained fatty acids from a microbially altered phytodetrital fatty acid pool, and Nephtys spp. from ice algal fatty acids acquired indirectly through predation. This multi-proxy compound-specific stable isotope approach was then applied to examine dietary overlap between Pacific walruses (Odobenus rosmarus divergens) and bearded seals (Erignathus barbatus) in 2009-2011 who feed primarily on benthic invertebrate prey. Differences in the relative proportions of fatty acids produced exclusively by benthic prey (non-methylene interrupted fatty acids) indicated that walruses and bearded seals had divergent diets. Proportional contributions of algal sources from ice, open ocean, and surface sediments to the prey consumed by walruses and bearded seals also varied. Walruses consumed prey that relied primarily on benthic and pelagic carbon sources (i.e., suspension/surface and subsurface deposit-feeding bivalves). In contrast, bearded seals consumed prey that relied on benthic and ice algal carbon sources (i.e., omnivorous and predatory benthic invertebrates). In conclusion, this research revealed that, in the recent study years, benthic food webs in the Alaska Arctic and sub-Arctic contained several trophic pathways linking consumers to distinct organic matter sources. Consequently, projected changes in algal production with future climate warming may elicit species-specific responses among benthic organisms.
    • Carbonate facies and sequence stratigraphy of the carboniferous Lisburne group, Upper Nanushuk River Region, Central Brooks Range, Alaska

      White, Jesse Garnett (2007-12)
      This study documents the stratigraphy, facies, facies associations, depositional environment, sequence stratigraphy, and conodont biostratigraphy of the upper Nanushuk River section of the Lisburne Group. 1621 meters of Kayak Shale and Lisburne Group rocks were measured and studied for facies analysis. Sixteen lithofacies and eleven microfacies were identified composing six facies assemblages. Facies analysis, stacking patterns, and associations suggest that the Nansushuk River section represents a homoclinal carbonate ramp recording an intertidal (Kayak Shale) and open marine to basin transitional sequence. Facies associations, stacking patterns and marine flooding surfaces helped to delineate major sequence boundaries and maximum flooding surfaces. Six 3rd order stratigraphic sequences have been identified in the Nanushuk River section. The section ranges in age from Osagean to lower Morrowan based on conodont biostratigraphy. The reservoir rock potential of the Nanushuk River section resides primarily in the dolomite of the Wachsmuth Limestone. The remainder of the section is considered 'tight' from a microfacies standpoint. Regionally, this study is important for paleogeographic reconstruction of the Lisburne Group across northern Alaska and adds to the general geologic knowledge of the Lisburne Group by obtaining stratigraphic data from a relatively isolated area in the Brooks Range.
    • Carboniferous Lisburne Group Carbonates Of The Porcupine Lake Valley: Implications For Surface To Subsurface Sequence Stratigraphy, Paleogeography, And Paleoclimatology

      Mcgee, Michelle Marie; Whalen, Michael T. (2004)
      This study utilizes high-resolution stratigraphy and sequence stratigraphy to document the response of the Carboniferous Lisburne Group carbonate platform during a change from greenhouse to icehouse conditions. The Lisburne Group in northern Alaska represents a laterally extensive carbonate ramp deposited on a passive continental margin during a greenhouse to icehouse transition. The Lisburne Group is subdivided into the Mississippian Wachsmuth and Alapah Limestones and Mississippian to Pennsylvanian Wahoo Limestone. I have identified six depositional sequences and corresponding systems tracts within the Lisburne Group based on bounding surfaces, cycle stacking patterns, and lateral lithofacies relationships. The Wachsmuth Limestone (Sequences I and II) is comprised of relatively thick cycles that have a "layer cake" stacking pattern that records minor migration of facies. Cycles in the uppermost Wachsmuth Limestone and the Alapah Limestone (Sequences III and IV) are thick, less "layer cake"-like, have deep water tongues at the base, and record significant migration of facies. Cycles in the uppermost Alapah Limestone and the Wahoo Limestone (Sequences V and VI) are thin, juxtapose deep water over shallow water facies, and record significant migration of facies. An unconformity marked by paleosols and karst features has been documented near the Mississippian-Pennsylvanian boundary in the Wahoo Limestone. I interpret the distinct change in cycle stacking patterns between the Mississippian and Pennsylvanian Lisburne Group to be related to changes in Paleoclimate. I interpret Sequences I through IV to be deposited during a greenhouse and transitional climate; whereas, Sequences V and VI were deposited during an icehouse climate.
    • Caribou migration, subsistence hunting, and user group conflicts in northwest Alaska: a traditional knowledge perspective

      Halas, Gabriela; Kofinas, Gary; Fix, Peter; Joly, Kyle (2015-08)
      Alaska Natives of northwest Alaska are highly dependent on barren-ground caribou (Rangifer tarandus) for meeting their nutritional and cultural needs. The Alaska Native village of Noatak borders the Noatak National Preserve (NNP), an area historically and presently used by Iñupiaq for subsistence caribou hunting and other traditional activities. Interactions between local and non-local caribou hunters were analyzed through the lens of common pool resource theory, which I linked to traditional Iñupiaq management of access and use of resources. This study examined changes in caribou migration and its effect on local caribou hunting success, which have been perceived to be the result of the interaction with non-local hunters and commercial aircraft operators transporting non-locals. Past research, decades old at this point, was undertaken prior to some regulations in place today, such as zoned use areas. To understand the implications of these changes, I documented the perceptions of local hunters by drawing on their traditional ecological knowledge (TEK), using a mixed methods approach to capture information on caribou ecology and human-caribou interactions. Mixed methods included a survey of active hunters, semi-structured participatory mapping interviews with local caribou experts of Noatak, key informant interviews, and participatory observation. Local hunters reported that caribou migration has changed, and there has been a decrease in the population of the region's caribou herd, the Western Arctic Herd (WAH). Hunters also reported that caribou hunting has changed substantially in the last five years, with fewer caribou harvested and hunters adapting to accommodate caribou migration shifts. Local hunters ranked aircraft and non-locals hunters as having the greatest negative impact to caribou migration and local hunting, followed by predation, climate change and habitat change. Noatak hunters perceived that their harvest of caribou is most impacted by non-local activity in the Noatak region. As well, local hunters reported that aircraft are a greater disturbance than on-the-ground non-local hunters. Participatory mapping revealed that use-areas are shared by local and non-local users along the Noatak River corridor, including both inside and outside zoned use areas. Suggestions by respondents for improved caribou management and conflicts with non-locals ranged from reducing non-local activity, working together with non-locals and aircraft operators, improving economic development for Noatak, and teaching youth of the village traditional hunting practices. Findings of this research demonstrate that local hunters have a rich, localized knowledge of human-caribou systems, which can contribute further to understanding of caribou-human interactions and in turn help to inform wildlife management decision-making.
    • Caries differences among Sub-Saharan Africans

      Carter, Fawn; Irish, Joel D.; Clark, Jamie; Hoover, Kara (2014-08)
      Teeth are a vital source of data for interpreting ancient lifestyles because of their high preservation potential and direct association with food. Understanding dental pathologies such as dental caries (cavities), can provide valuable information regarding diet and health. The objective of the present study is to compare caries prevalence among sub-Saharan African populations to determine whether any significant differences exist through space, time, economy, and between the sexes. A few small-scale dental pathology studies have been undertaken on specific populations and regions, but until now none have encompassed the entirety of sub-Saharan Africa from the Late Stone Age through modern times. Data on caries counts and severity from 1963 individuals comprising 44 sub-Saharan samples are compared using Mann-Whitney U and factorial ANOVA statistics. Results suggest: 1) major changes in diet related to widespread movement of people caused a general increase in caries; 2) there is no statistically significant difference in the frequency of caries between males and females; 3) people living in the savanna have more caries because of their dependence on high carbohydrate foods; and 4) subsistence strategy plays a role in caries frequencies. These findings reveal that global trends in caries susceptibility as described by other researchers do not always apply and that each population should be considered in turn.
    • Caries prevalence in ancient Egyptians and Nubians

      Triambelas, Konstantine; Irish, Joel; Hoover, Kara; Clark, Jamie (2014-08)
      This thesis presents an expanded bioarchaeological perspective to quantitative analyses of dental caries in the remains of 1842 ancient Egyptians and Nubians. The skeletal samples from 17 Egyptian and 15 Nubian cemeteries are represented by both sexes, and span a period from 14000 BCE-1450 CE. Considering that a skeletal population of this size has never been previously evaluated for dental caries, this thesis can make a considerable contribution to a better understanding of the variability encountered in dental caries patterns over time, as these are manifested within the bio/cultural/ecological context of the Nile Valley. Dental caries are the decomposition of tooth enamel resulting from the chemical breakdown of dietary carbohydrates by oral bacteria. In archaeological populations, increasing rates of dental caries have been positively correlated with consumption of agriculturally-based cereals such as wheat and barley. Dental caries rates thus provide a reliable indicator of human biocultural transitions to agriculture, as well as information on diet, general oral health, and social organization of the group. In the context of ancient Egypt and Nubia, dental caries frequencies have been previously used to evaluate regional variability in dietary practices, as well differential access to resources based on sex and social class/status. This thesis reevaluates much of the above information using a larger and more statistically-representative sample. Quantitative analyses based on both non-parametric and parametric statistical techniques were used to assess intra- and inter-sample differences in mean tooth caries, mean individual caries, and mean ante mortem tooth loss (AMTL). These variables were compared across samples by region, time period, economic organization, sex, and social status. Results for Egypt were in agreement with previous research showing overall low caries prevalence increasing through time. Significant regional and inter-cemetery differences existed between Lower Egypt and Upper Egypt, as well as between late Dynastic samples and earlier ones. In Nubia, significant differences according to region and sex were shown to exist in the prehistoric/preagricultural component of the study. In contrast with previous findings, Nubian dental caries were higher in the earlier phases and declined during the agriculturally-intensive periods of later Nubian history. The exception to this last finding was the Christian period when both dental caries and AMTL experienced considerable increases.
    • Carpenters daughter

      Osier, Jill N. (2000-05)
      Carpenter's Daughter reveals the construction and reconstruction a woman understands her life to be. Acknowledging the creation of identity through the tools of history, memory, dream, and imagination, it further explores where these worlds converge at different points along the path from child to girl to woman. The poems are equally concerned with dynamics beyond a sense of self--particularly how things come together and come apart. In both the realm of nature and that of human emotion, the speakers are confronted by tenuous connections and surprising holds, moved by the frailties lying beneath solid foundations and the grace witnessed in failing frames. Though several poems use formal patterns of line or stanza, most work in free verse and are driven by narrative, image, or voice. These also provide thematic links throughout the collection, their echoes serving to fully present ideas as well as celebrate sound.
    • Carving Alaska Soapstone

      Eubank, Mary Louise Reed (1968)
    • A case/control analysis and comparison of indoor air quality in Alaskan homes

      Dinakaran, Satish; Johnson, Ron; Naidu, Sathy; Lin, Chuen-Sen; Seifert, Rich (2005-08)
      Indoor Air Quality (IAQ) parameters such as CO, CO₂, relative humidity, temperature, radon, particulate matter, formaldehyde, benzene, toluene, hexane, Total Volatile Organic Compounds (TVOC) and microbial matter were monitored before and after remediation in 36 low-income homes in Alaska (Hooper Bay and Fairbanks). The objective was to see if there was any improvement in IAQ with remediation. Hooper Bay homes had significantly higher levels of CO₂ and relative humidity compared to Fairbanks homes both before and after remediation. There was a general reduction in CO₂ with remediation, although it was not statistically significant. When IAQ in two moderate-income homes in Fairbanks was compared with that in the remediated low-income homes, it was observed that indoor CO₂ levels were affected by ventilation rates and per capita floor area. A single zone model to predict concentration of indoor pollutants was constructed, using steady state and transient mass conservation, to predict, metabolically produced CO₂, and particulate matter when no indoor sources were present. The cost of energy to reduce indoor CO₂ levels in one of the homes by increasing ventilation by either using an exhaust-only system or a Heat Recovery Ventilator (HRV) is discussed.
    • Causes and consequences of coupled crystallization and vesiculation in ascending mafic magmas

      Lindoo, Amanda N.; Larsen, Jessica F.; Freymueller, Jeffrey; Izbekov, Pavel; Trainor, Tom (2017-08)
      Transitions in eruptive style and eruption intensity in mafic magmas are poorly understood. While silicic systems are the most researched and publicized due to their explosive character, mafic volcanoes remain the dominant form of volcanism on the earth. Eruptions are typically effusive, but changes in flow behavior can result in explosive, ash generating episodes. The efficiency of volatiles to degas from an ascending magma greatly influences eruption style. It is well known that volatile exsolution in magmas is a primary driving force for volcanic eruptions, however the roles vesicles and syn-eruptive crystallization play in eruption dynamics are poorly understood. Permeability development, which occurs when gas bubbles within a rising magma form connected pathways, has been suspected to influence eruption style and intensity. Numerous investigations on natural eruptive products, experimental samples, and analog experiments have extended the understanding of permeability development and fragmentation processes. However, these studies have focused on silicic, high viscosity, crystal-poor magmas. Little progress has been made in understanding fragmentation mechanisms in mafic or alkali magmas. Mafic systems involve lower viscosity magmas that often form small crystals, also known as microlites, during ascent. Because the merging of bubbles in magma is mitigated by melt viscosity, it is predicted that permeability development in mafic magma will occur at lower bubble volume fractions than in silicic magma. However, no study has been performed on experimental samples to provide evidence for this hypothesis. Furthermore, it is unknown how microlites affect the degassing process in terms of facilitating or hindering permeability development. This thesis employs experimental petrology to: 1) experimentally observe how melt viscosity alone affects permeability development, 2) Understand the effects of syn-eruptive crystallization in vesiculating mafic magmas and synergizes these results to 3) relate experimental findings to the 2008 eruption of Kasatochi volcano.
    • Causes and consequences of geophagy in snowshoe hares (Lepus americanus), an important generalist herbivore of the boreal forest

      Worker, Suzanne; Kielland, Knut; Barboza, Perry; Ruess, Roger (2013-12)
      Geophagy, the consumption of mineral soil, is believed to have several benefits for herbivores. Soils high in clay are often implicated in the detoxification of plant secondary metabolites. High mineral concentrations in soils may also provide nutrients that are poorly available from plants. Local observers report that snowshoe hares (Lepus americanus) use a lick in the foothills of the Brooks Range, Alaska. Using soil from this lick and other mineral supplements, I conducted a series of feeding trials on captive snowshoe hares fed felt-leaf willow (Salix alaxensis) or a formulated ration to determine whether geophagy resulted in a physiological benefit and, if so, which soil constituents are therapeutic. When fed willow leaves, hares ate more and lost less weight when they had access to soil. Access to soil increased sodium intake and dietary ratios of sodium to potassium in hares fed willow. Soil consumption resulted in higher calcium to phosphorous ratios for both diets. Across diets, higher sodium to potassium and lower calcium to phosphorus ratios corresponded to reduced weight loss. Access to pure calcium carbonate resulted in reduced weight loss in hares fed winter dormant willow twigs, suggesting that carbonates may also be an important component of this lick.
    • Causes and consequences of variable extrafloral nectar secretions in quaking aspen (Populous tremuloides Michx.)

      Newman, Jonathon R.; Wagner, Diane; Doak, Patricia; Green, Thomas (2014-05)
      Extrafloral (EF) nectaries mediate a defensive mutualism in many plant populations, wherein plants attract predatory arthropods by providing nectar rewards. The primary objectives of this study were to identify abiotic and biotic factors that may affect secretion by EF nectaries in quaking aspen (Populus tremuloides Michx.) and to determine how variation in secretion rate affects attractiveness of P. tremuloides ramets to predatory arthropods such as ants. I investigated the effects of water stress, defoliation, and genotype on extrafloral sugar secretions in P. tremuloides and tested how variations in EF sugar quantity affect ant visitation to P. tremuloides ramets in interior Alaska. Additionally, I analyzed P. tremuloides sugar composition from three genotypes. Extrafloral sugar secretions were inducible by defoliation, and the induction response was not inhibited by water stress. Irrespective of defoliation, water stress had a variable effect on sugar secretion rates between genotypes, with one out of four genotypes exhibiting a reduction in secretion rate in response to low water availability. Genotypes differed in secretion rates overall, which could potentially influence defensive levels among clonal stands. Ant visitation to ramets with experimentally increased sugar availability was increased for one of three genotypes in early summer, though in mid-summer ants did not respond to nectar supplementation. There was no effect of nectar reduction on ant visitation in either early or mid-summer trials. Genotypes attracted different average numbers of ants, which may have been a result of intrinsic variation in volatile organic compound emission, EF nectar secretion rates, or nectar composition. Analysis of EF sugar secretions of P. tremuloides using nuclear magnetic resonance spectroscopy revealed that EF nectar tends to be dominated by sucrose over glucose and fructose. This composition may increase attractiveness to mutualistic ant species, which tend to favor sucrose dominated nectar blends. This study expands our knowledge of the sources of variation in EF nectar secretion and their impact in a widespread, ecologically important tree species.
    • Cecal Function In Ptarmigan

      Gasaway, William Clifton (1974)
    • Cenozoic tectono-thermal history of the southern Talkeetna Mountains, Alaska: multiple topographic development drivers through time

      Terhune, Patrick J.; Benowitz, Jeffrey; Freymueller, Jeffrey; Gillis, Robert (2018-08)
      Intraplate mountain ranges can have polyphase topographic development histories reflecting diverse plate boundary conditions. We apply ⁴⁰Ar/³⁹Ar, apatite fission track (AFT) and apatite (U-Th)/He (AHe) geochronology-thermochronology to plutonic and volcanic rocks in the southern Talkeetna Mountains of Alaska to document regional magmatism, rock cooling and inferred exhumation patterns as proxies for the deformation history of this long-lived intraplate mountain range. High-temperature ⁴⁰Ar/³⁹Ar geochronology on muscovite, biotite and K-feldspar from Jurassic granitoids indicates post-emplacement (~158-125 Ma) cooling and Paleocene (~61 Ma) thermal resetting. ⁴⁰Ar/³⁹Ar whole rock volcanic ages and AFT cooling ages in the southern Talkeetna Mountains are predominantly Paleocene-Eocene, suggesting that the Range is partially paleotopography that formed during an earlier tectonic setting. Miocene AHe cooling ages within ~10 km of the Castle Mountain Fault suggest ~2-3 km of vertical displacement that also contributed to mountain building, likely in response to the inboard progression of the subducted Yakutat microplate. Paleocene-Eocene volcanic and exhumation ages across interior southern Alaska north of the Border Ranges Fault System are similar and show no N-S or W-E progressions, suggesting a broadly synchronous and widespread volcanic and exhumation event that conflicts with the proposed diachronous subduction of an active west-east sweeping spreading ridge beneath south-central Alaska. To reconcile this, we propose a new model for the Cenozoic tectonic evolution of southern Alaska. We infer that slab breakoff sub-parallel to the trench and subsequent mantle upwelling drove magmatism, exhumation and rock cooling synchronously across south-central Alaska and played a primary role in the development of the southern Talkeetna Mountains.
    • Central CO2 chemosensitivity in tadpoles: impairment and the role of serotonin

      Audie, Spencer D.; Taylor, Barbara E.; Harris, Michael B.; Duffy, Lawrence K. (2012-05)
      Nicotine and ethanol are known neuroteratogens and prenatal exposure correlates with Sudden Infant Death Syndrome (SIDS), which is thought to result from failure to maintain pH homeostasis through respiratory adjustments. This failed homeostatic control is believed to be serotonergic in origin. In previous studies nicotine or ethanol exposure ablated the robust hypercapnic response of early-stage tadpoles. These findings lead us to question if the ablation occurred through a serotonindependent mechanism. This study investigated the role of serotonin (5- HT) in the nicotine- or ethanol-induced abolishment of the hypercapnic response. We found that toxin-exposed animals were insensitive to hypercapnia and also failed to respond to concomitant exposure to hypercapnia and 8-OH-DPAT, supporting our hypothesis that toxininduced abolishment of the hypercapnic response is mediated by 5-HTia receptors. Immunofluorescence data from brainstem slices of ethanolexposed animals showed a decrease in 5-HTia receptors and the serotonin-synthesizing enzyme tryptophan hydroxylase. In contrast, 3- wk nicotine-exposed animals displayed no significant difference in immunofluorescence for either protein. Taken together the electrophysiological and immunofluorescence data suggest the effects of ethanol or nicotine exposure, which impair the hypercapnic response, include a failure of serotonergic signaling and that this failure is not simply the reflection of a global reduction in serotonin levels.
    • Central Nervous System Regulation Of Metabolic Suppression In Arctic Ground Squirrels

      Jinka, Tulasi Ram; Drew, Kelly L. (2010)
      The main focus of this dissertation is central nervous system regulation of metabolic suppression in hibernating mammals in general, and the Arctic ground squirrel (Urocitellus parryii) as a model for seasonal hibernation. Hibernation is a unique physiological, morphological, and behavioral adaptation to overcome the periods of resource limitation. Metabolic suppression seen in torpor during hibernation has several biomedical applications. A multitude of studies have revealed the role of the central nervous system in regulating hibernation, including a role for neurotransmitters and neuromodulators. Previous studies have shown that the neuromodulator adenosine mediates altered thermoregulation during induction of torpor in facultative hibernators, but it is not clear how adenosine influences torpor in seasonal hibernators. The main focus of the current project was to test the hypothesis that a seasonal change in purinergic signaling is necessary for the onset of spontaneous torpor in the Arctic ground squirrel. My dissertation reports that adenosine meets all of the necessary requirements for an endogenous mediator of torpor in the hibernating Arctic ground squirrel. A progressive increase in sensitivity to adenosine A 1 receptors mediated signaling defines the seasonal transition into the hibernation phenotype. I show that adenosine A1 receptor activation is necessary and sufficient to induce torpor in the Arctic ground squirrel. Glutamate is an excitatory neurotransmitter which is widely studied in hibernation research. My dissertation demonstrates that N-methyl-D-aspartate type glutamate receptors, located in the periphery or circumventricular organs, are involved in inducing arousal from torpor in the hibernating Arctic ground squirrel. This dissertation also presents evidence that dietary restriction sensitizes adenosine A1receptors in rats through an increase in surface expression in thermoregulatory regions of the brain (hypothalamus). This contributes to the decline in body temperature and respiratory rate in animals subjected to a restricted diet, which mimics a torpor-like effect.