• Tobacco use and cessation: What matters to Southeast Alaska Native young adults?

      Anderson, Kathryn; Johnson, Rhonda; Lopez, Ellen; Bryant, Carol; Garcia, Gabriel; Lardon, Cecile; Skewes, Monica (2013-12)
      Background: The smoking rate among young Alaska Native adults (ages 19-29) in Southeast Alaska is 70% as compared to the statewide adult smoking rate of 21%, the Alaska Native adult rate of 41%, and the overall young adult rate of 32%. Southeast Alaska Regional Health Consortium (SEARHC), the non-profit tribal health consortium serving Southeast Alaska, commissioned this research to inform development of a young adult-specific, social marketing-based smoking cessation intervention. Methods: Using purposive sampling, 23 individuals were recruited for five focus groups and four individual interviews in Juneau, Alaska. Following a social marketing framework, the research assessed participant beliefs about the benefits and negative impacts of smoking, barriers to quitting, and preferred quit support methods, as well as participant reactions to particular anti-smoking advertisements and quit support methods. Results: Almost all participants reported an interest in quitting smoking. Stress relief, boredom relief, relaxation, and oral satisfaction were the main benefits of smoking. Downsides to smoking included negative short-term health impacts, negative impacts on children in the extended family, and negative cosmetic impacts. Barriers to quitting included loss of listed benefits, addiction and habit, fatalism, and the high prevalence of smoking among family and friends. The preferred method of quitting was cold turkey (unassisted quitting), with very few participants reporting use of counseling or pharmacotherapy. Participants preferred high emotional level anti-smoking advertisements with either strongly negative emotional valence (e.g., fear and disgust) or strongly positive emotional valence (e.g., joy, happiness). Reaction to quit support methods was most favorable to texting support and a smart phone app, and most negative toward a smart phone video game. Reaction to counseling was strongly supportive among those who had tried it and largely but not totally negative among those who had not. Conclusion: Young Alaska Native adults in Juneau who smoke are interested in quitting but prefer cold turkey to counseling and pharmacotherapy. They are more concerned about short-term than long-term health impacts, and they are sensitive to the impact of smoking on their appearance and on children in their extended family. Findings formed a foundation for a proposed social-marketing based intervention.
    • Tomo ni manabu: task-based language teaching in a high school English class in Japan

      Holland, Yoshie; Siekmann, Sabine; Murakami, Chisato; Martelle, Wendy (2019-08)
      Task-based language teaching is a method that emerged in the field of second language acquisition in the U.S. Task-based language teaching facilitates language learning in context. However, there are few examples of research that investigate the applicability of task-based language teaching in classrooms in Japan where constraints such as big class size, college entrance exams, and designated textbooks that follow the national curriculum guidelines are factors. This study investigates the response of a Japanese teacher and 41 high school students in Japan, the students' language development as well as the suitability of task-based language teaching in classrooms in Japan. It also offers some guidance to make task-based language teaching more easily applicable to classrooms in Japan. This mixed method study involved a series of semi-structured interviews with a high school teacher in Japan, class observations of the task-based language teaching lessons, and a pre-test and post-test with surveys for the students. The study found out that the teacher expressed tensions between his current teaching context at that time and the task-based language teaching lesson plan. However, the teacher finished the lesson with a positive attitude towards task-based language teaching. Also, the students learned the grammar focus from the task-based language teaching lesson even though the lesson was not focused on the grammar as much as the traditional teaching. Overall, task-based language teaching in the teaching context worked well where the students worked in groups since it facilitated learning among students. This study also suggests that the teacher and his students adopted task-based language teaching positively and that the specific approach of task-supported language teaching is likely to be most suitable in this teaching context.
    • Toolstone procurement in middle-late Holocene in the Kodiak archipelago and the Alaska Peninsula

      Rains, Devon; Potter, Ben; Severin, Ken; Rasic, Jeffrey; Irish, Joel (2014-12)
      The Norton tradition (2300-950 BP) in the Alaska Peninsula and the Late Kachemak phase (2700-900 BP) in Kodiak are distinct cultural traditions yet contain some similarities in lithic assemblages and house form, suggesting some contact or influence occurred. The subsequent Koniag tradition (900-200 BP) is present in both the Alaska Peninsula and Kodiak, indicating direct influence or migration. While the Koniag tradition is found in sites located throughout the North Pacific region, the Koniag tradition in Kodiak is characterized by changes in social climate and subsistence strategies including greater warfare/raiding and resource consolidation. In order to obtain these resources, Koniag populations living in Kodiak may have traveled farther distances than previous populations. In contrast, Alaska Peninsula populations did not experience significantly different subsistence strategies over time and therefore would not need to travel as far as Kodiak populations or significantly alter subsistence patterns. Determining the probable origins of toolstone materials in late prehistoric sites can reveal changes in the ways people in this region obtained their resources and give a more comprehensive understanding of the degree to which the Koniag lifestyle differed from the preceding cultural traditions in the region. Due to the eruptive history in the Alaska Peninsula, the presence of volcanic toolstone in Kodiak sites, and the close proximity between the two locations, central Alaska Peninsula and Kodiak sites are optimally located in order to determine possible changes in the direction where volcanic toolstone originated. This thesis explored differences between volcanic toolstone procurement locations in late prehistoric sites on the Kodiak Archipelago and the central Alaska Peninsula by comparing samples according to size and abundance of tool types, site location, cultural affiliation, and time periods using element values obtained from x-ray fluorescence (XRF) technology. Results show possible geographic boundaries of toolstone containing similar element values using Alaska Peninsula samples, which were subsequently compared with Kodiak samples. Data presented in this thesis shows the geographic range of likely toolstone procurement locations increased over time in Kodiak sites, while Alaska Peninsula sites contain evidence that toolstone remained locally procured over time.
    • Toothed whale interactions with longline fisheries in Alaska

      Peterson, Megan J.; Carothers, Courtney; Mueter, Franz; Matkin, Craig; Criddle, Keith (2014-05)
      Killer whale (Orcinus orca) and sperm whale (Physeter macrocephalus) depredation occurs when whales damage or remove fish caught on longline gear. This project used a mixed methods approach incorporating Generalized Linear and Additive Modeling techniques and social research methods, such as semi-directed interviews and written questionnaires, to evaluate: 1) spatio-temporal depredation trends, 2) depredation effects on groundfish catch rates, and 3) socio-economic implications of depredation avoidance and changing fishing practices due to whale interactions. The occurrence of killer whale depredation varied by target species and area based on National Marine Fisheries Service longline survey data and observer commercial fishery data collected from 1998 to 2012 in the Bering Sea, Aleutian Islands, and Western Gulf of Alaska. The percentage of commercial fishery sets affected by killer whales was highest in Bering Sea fisheries for: sablefish (Anoplopomafimbria; 21.4%), Greenland turbot (Reinhardtius hippoglossoides; 9.9%), and Pacific halibut (Hippogolossus stenolepis; 6.9%). Killer whale depredation was more common on the standardized longline survey (9.2-34.6% skates impacted) than the commercial sablefish fishery (1.0-21.4% sets impacted) in all three management areas. Catch reductions were consistent across data sets. Average commercial fleet catch reductions ranged from 35-69% for sablefish, Pacific halibut and Greenland turbot (p<0.001); survey catch reductions ranged from 51-73% (p<0.001). Sablefish catch per unit effort, gear haul time and location significantly impacted the proportion of sets depredated. Fishermen reported changing their fishing practices in response to depredating whales by soaking gear longer to "wait the whales out" or moving to different fishing sites. These avoidance measures resulted in increased operation costs and opportunity costs in lost time. In a follow-up analysis based on data collected by fishermen in 2011 and 2012, it was found that killer whale depredation avoidance measures resulted in an average additional cost of $494 per vessel-day for fuel and crew food. Opportunity costs of time lost by fishermen averaged $486 per additional vessel-day on the grounds. These results provide insight into the potential impacts of whale depredation on fish stock abundance indices and commercially important fisheries in Alaska and will inform future research on apex predator-fisheries interactions.
    • A total environment of change: exploring social-ecological shifts in subsistence fisheries in Noatak and Selawik, Alaska

      Moerlein, Katie J. (2012-05)
      Arctic ecosystems are undergoing rapid changes as a result of global climate change, with significant implications for the livelihoods of arctic peoples. In this thesis, I use ethnographic research methods to detail prominent environmental changes observed and experienced over the past few decades and to document the impact of these changes on subsistence fishing practices in the Inupiaq communities of Noatak and Selawik in northwestern Alaska. Using in-depth key informant interviews, participant observation, and cultural consensus analysis, I explore local knowledge and perceptions of climate change and other pronounced changes facing the communities of Noatak and Selawik. I find consistent agreement about a range of perceived environmental changes affecting subsistence fisheries in this region, including lower river water levels, decreasing abundances of particular fish species, increasingly unpredictable weather conditions, and increasing presence of beaver, which affect local waterways and fisheries. These observations of environmental changes are not perceived as isolated phenomena, but are experienced in the context of accompanying social changes that are continually reshaping rural Alaska communities and subsistence economies. Consequently, in order to properly assess and understand the impacts of climate change on the subsistence practices in arctic communities, we must also consider the total environment of change that is dramatically shaping the relationship between people, communities, and their surrounding environments.
    • Tourism development and public policy: perceptions of the Chuukese community

      Perez, Gerald San Agustin; Baek, Jungho; Schumann, Fred; Caroll, Jennifer; Walter, Ansito (2019-05)
      Tourism is a widely used tool for economic development in small insular communities. This mixed methods study examines factors that influence residents' perceptions toward tourism development in Chuuk and the relevance of "complexity theory" in describing the island's stage of development. Empirical evidence and data triangulation corroborate general support for tourism development and sensitivity to cultural impacts, economic impacts, social impacts, environmental impacts, local control and sustainability. Economic and cultural impacts were the strongest factors influencing perceptions and are most significant to sustainable development and destination development. This reflects residents' beliefs that the island will benefit from tourism because of perceived improvements in the economy, infrastructure, tourist facilities and expanded social amenities. It also reflects residents' expectations for long term planning, managed growth, and laws to protect the environment. Some differences and similarities are noted between sampled residents living in Chuuk and Guam. This study is the first of its kind in an isolated region lacking scholarship literature on tourism. As such, basic information gathered is a wellspring, for further research into issues of social justice using a more sequential transformative framework.
    • Touristic encounters of an intercultural kind: communication between volunteers and international visitors at a visitors information center

      Peterson, Sherrill Lea (2004-05)
      This qualitative research examined the lived experience of volunteers in providing information to international travelers at a Visitors Information Center. The research focused on intercultural communication during these touristic encounters. Interpersonal communication and meaning engagement practices between volunteer information providers and international visitors were examined from a narrative theoretical perspective. Narratives of six volunteer information providers were gathered using conversational interviews and analyzed using the method of thematic analysis. Six themes emerged from volunteers' narratives of their experience: independent/package tour travelers, visitors' expectations, information as product/process, foreign language skills, adaptability and accommodation, and public inebriation of homeless local residents. Contrary to expectations, volunteers reported that the experience of providing information for international visitors was very little different from providing information to visitors with cultural patterns of communication similar to their own. Several explanations are offered for the apparent absence of difficulties in providing information to international visitors. The surprising finding warrants further research.
    • Toward an optimal solver for the obstacle problem

      Heldman, Max; Bueler, Ed; Maxwell, David; Rhodes, John (2018-04)
      An optimal algorithm for solving a problem with m degrees of freedom is one that computes a solution in O (m) time. In this paper, we discuss a class of optimal algorithms for the numerical solution of PDEs called multigrid methods. We go on to examine numerical solvers for the obstacle problem, a constrained PDE, with the goal of demonstrating optimality. We discuss two known algorithms, the so-called reduced space method (RSP) [BM03] and the multigrid-based projected full-approximation scheme (PFAS) [BC83]. We compare the performance of PFAS and RSP on a few example problems, finding numerical evidence of optimality or near-optimality for PFAS.
    • Toward Arctic transitions and sustainability: modeling risks and resilience across scales of governance

      Blair, Berill; Lovecraft, Amy Lauren; Kofinas, Gary P.; Eicken, Hajo; Haley, Sharman; Meek, Chanda (2017-08)
      The Arctic region has been the subject of international attention in recent years. The magnitude of impacts from global climate change, land-use change, and speculations about economic development and accessible polar shipping lanes have intensified this focus. As a result, the potential to manage complex ecological, social and political relationships in the context of changes, risks and opportunities is the focus of a large and growing body of research. This dissertation contributes to the expanding scholarship on managing Arctic social-ecological systems for resilience by answering the question: What conditions improve cross-scale learning and resilience in nested social-ecological systems experiencing rapid changes? Using the framework of social-ecological systems and the drivers of change that can transform fundamental relationships within, three studies profile the spatial and temporal dimensions of learning and risk perceptions that impact nested social systems. The first study presents a spatial and temporal analysis of scale- and level-specific processes that impact learning from risks. It draws on four cases to underscore the need for a plurality of risk assumptions in learning for resilience, and sums up essential resources needed to support key decision points for increasing resilience. Two additional studies present research conducted with northern Alaska communities and resource managers. In these studies, I analyzed the extent to which perceptions of risks scale horizontally (between same-level jurisdictions), and vertically (between levels in a dominant jurisdictional structure). These examples illustrate the need for innovative institutions to enhance cross-scale learning, and to balance global drivers of change with local socioeconomic, cultural, and ecological interests. Based on findings of the dissertation research I propose recommendations to optimize the tools and processes of complex decision making under uncertainty.
    • Toward computer generated folk music using recurrent neural networks

      Weeden, Rohan E.; Lawlor, Orion; Chappell, Glenn; Genetti, Jon (2019-05)
      In this paper, we compare the effectiveness of two different types of Recurrent Neural Networks, fully connected and Long Short Term Memory, for modeling music compositions. We compare both the categorical accuracies of these models as well as the quality of generated compositions, and find that the model based on Long Short Term Memory is more effective in both cases. We find that the fully connected model is not capable of generating non repeating note sequences longer than a few measures, and that the Long Short Term Memory model can do significantly better in some cases.
    • A toxicity assessment of total dissolved solid ions in mine effluent using two common bioassays: the 22-hour MicroTox assay and a S. carpricornutum growth assay

      LeBlond, Jane Benton (2000-05)
      This research evaluated two microassays and a synthetic TDS standard to measure the effects of elevated TDS from mine effluent on biota of freshwater systems. Field samples from Red Dog and Fort Knox mines were tested on Selenastrum capricornutum and the MicroTox assay, and compared to the synthetic standard. Results indicate that the synthetic TDS standard is a poor representation of produced waters with similar total TDS concentrations. Additionally, no correlation was found between the toxicological responses of the two assays. Principle component analysis found the MicroTox assay to be most sensitive to cadmium and chloride. At concentrations present in the field samples, there does not appear to be a relationship between toxicity and TDS as measured on these assays.
    • The toxicity of creosote treated wood to pacific herring (Clupea pallasi) embryos and characterization of polycyclic aromatic hydrocarbons near creosoted pilings in Juneau, Alaska

      Duncan, Danielle; Stekoll, Michael; Rice, Stanley; Perkins, Robert; Gharrett, Anthony (2014-08)
      These studies documented creosote toxicity to developing Pacific herring (Clupea pallasi) embryos at low microgram per liter concentrations and determined that detrimental concentrations of polycyclic aromatic hydrocarbons (PAHs) near creosoted pilings exist. Creosote total PAH concentrations of 7 μg/L resulted in skeletal defects and ineffective swimming in hatched larvae and represent a lowest observed effect concentration (LOEC) for Pacific herring embryos not previously defined. In the field, PAHs consistent with creosote were elevated at distances up to a meter from creosoted pilings in some cases. Concentrations likely sufficient to induce teratogenic effects were found directly on creosoted pilings and within ten centimeters of pilings. Cumulatively, these studies provide useful and needed data on the interactions between Pacific herring embryos and creosoted pilings in the nearshore environment.
    • Toxicodistribution of mercury and selenium in pinnipeds of Alaska

      Correa, Lucero; O'Hara, Todd; Rea, Lorrie; Hueffer, Karsten; Cahill, Catherine; Trainor, Tom (2013-12)
      This study is divided into two major parts (chapters) in order to better understand mercury (Hg) and selenium (Se) tissue distribution in pinnipeds. The first part of the study focuses on determining total mercury ([THg]) and selenium ([TSe]) concentrations (mass and molar based) among cardiac and renal tissues of ice seals (focus on bearded seals, Erignathus barbatus) as compared to the more traditionally analyzed tissues (e.g. liver, skeletal muscle). Determining Hg distribution within these tissues is essential in establishing sampling methods for biomonitoring, histopathology and biochemistry of Hg. Age was determined to be an important driver of [THg] and Se:Hg molar ratios in heart and kidney. In bearded seals [THg] varied by heart region and therefore future studies should use consistent sampling methods in order to determine and compare [THg]. Despite the differences in seal kidney structure when compared to many terrestrial mammals, the kidney cortex was the main accumulation site for Hg within the kidney of bearded seals and requires consideration in sampling designs. Se:Hg molar ratios greater than 1 in all tissues can be considered a baseline for normal Se concentrations under relatively low [THg]. The second part of the study focuses on THg and TSe distribution in Steller sea lion (Eumetopias jubatus) pup tissues in addition to THg tissular and body burdens. Hair had the highest [THg] in all 5 Steller sea lion pups as compared to other tissue compartments. Since these pups were 1-2 months of age, the hair (lanugo) sampled was a good indicator of Hg exposure via maternal placental transfer (in utero) and potentially a good indicator of individual THg tissue burdens. The percent of total Hg body burden for many organs in Steller sea lion pups was similar to that found in Pacific harbor seals. The Se:Hg molar ratios were between 1 and 50 in all tissues of 4 of the 5 pups while the pup with the highest [THg] in all tissues, had Se: Hg molar ratios of 0.7 or less in 9 of 14 tissues indicating that this animal may have limited Se-dependent protection related to Hg toxicosis.
    • Toxins And Toxicity Of Protogonyaulax From The Northeast Pacific

      Hall, Sherwood (1982)
      Dinoflagellates of the genus Protogonyaulax contain a group of substances that can be lethal to many creatures, including man, and may accumulate at many points in the food web. The substances are most familiar as paralytic shellfish poison (PSP), which occurs sporadically in bivalves. The present study was undertaken because previous work left in doubt both the origin and chemical nature of the toxins along the Alaskan coast. To investigate the problem, dinoflagellates were isolated from locations along the Pacific coast ranging from San Francisco to Dutch Harbor. Most isolates were obtained by incubating subtidal sediments to germinate resting cysts. Toxic isolates were obtained from most locations sampled. On the basis of morphology, all toxic isolates fell within the genus Protogonyaulax. The growth and toxicity of one clone (PI07) was studied under a variety of culture conditions. Toxicity was greatly suppressed under the conditions traditionally employed for culturing Protogonyaulax, suggesting that the toxicity of cells in nature may in general be higher than has been recognized. Chemical studies of the toxins extracted from Protogonyaulax revealed that the six toxins previously known (saxitoxin, its N-1-hydroxyl and 11-hydroxysulfate derivatives) are generally accompanied by somewhat larger amounts of their 21-sulfo derivatives. These have likely not been recognized in past studies due to their greatly reduced toxicity, facile hydrolysis, and altered chromatographic properties. The toxin composition of several isolates was determined and indicates that toxin composition is a conservative property of each clone and that there are regional populations of Protogonyaulax with uniform toxin composition, but that toxin composition differs substantially among regions. This pattern of variation, coupled with the great differences in the properties of the toxins, indicates that the nature of PSP will similarly vary from one region to another but will be uniform within each.
    • Toxins and toxicity of Protogonyaulax from the Northeast Pacific

      Hall, Sherwood (1982-12)
      Dinoflagellates of the genus Protogonyaulax contain a group of substances that can be lethal to many creatures, including man, and may accumulate at many points in the food web. The substances are most familiar as paralytic shellfish poison (PSP), which occurs sporadically in bivalves. The present study was undertaken because previous work left in doubt both the origin and chemical nature of the toxins along the Alaskan coast. To investigate the problem, dinoflagellates were isolated from locations along the Pacific coast ranging from San Francisco to Dutch Harbor. Most isolates were obtained by incubating subtidal sediments to germinate resting cysts. Toxic isolates were obtained from most locations sampled. On the basis of morphology, all toxic isolates fell within the genus Protogonyaulax. The growth and toxicity of one clone (PI07) was studied under a variety of culture conditions. Toxicity was greatly suppressed under the conditions traditionally employed for culturing Protogonyaulax, suggesting that the toxicity of cells in nature may in general be higher than has been recognized. Chemical studies of the toxins extracted from Protogonyaulax revealed that the six toxins previously known (saxitoxin, its N-1-hydroxyl and 11-hydroxysulfate derivatives) are generally accompanied by somewhat larger amounts of their 21-sulfo derivatives. These have likely not been recognized in past studies due to their greatly reduced toxicity, facile hydrolysis, and altered chromatographic properties. The toxin composition of several isolates was determined and indicates that toxin composition is a conservative property of each clone and that there are regional populations of Protogonyaulax with uniform toxin composition, but that toxin composition differs substantially among regions. This pattern of variation, coupled with the great differences in the properties of the toxins, indicates that the nature of PSP will similarly vary from one region to another but will be uniform within each.
    • The trace formulas for a half-line Schrodinger operator with long-range potentials

      Belov, Sergei M. (2002-12)
      The present work deals with trace formulas for a half-line Schrödinger operator with long-range potentials. These formulas relate the potential with some scattering data. We generalize some relevant results by Buslaev; Faddeev; Gesztesy, Holden, Simon, and others to the case of square integrable potentials. The relation between the number of the trace formulas and the number of integrable derivatives of the potential is also given.
    • Trace metals in Arctic fast ice

      Domena, Vincent; Aguilar-Islas, Ana; Rember, Robert; McDonnell, Andrew (2017-12)
      Trace metals in the marine environment are found in trace amounts, but are important tracers of oceanographic processes, and bioactive trace metals can impact ocean biogeochemistry through their nutrient or toxic influence of microbial populations. Sea ice is an intrinsic feature of the Arctic Ocean that likely plays a key role in the cycling of trace metals, given that this substrate can concentrate, alter, and transport these elements. Warming conditions in the Arctic have decreased sea ice cover over the past decades and the loss of sea ice threatens to drastically change the Arctic ecosystem, but the implications are not entirely understood. The scarcity of studies on Arctic sea ice entrained trace metals is due in part to the lack of commercially available sampling equipment capable of collecting sea ice without introducing contamination, and in part to the logistic and economic difficulties in accessing remote Arctic sea ice sites. Natural heterogeneity related to large sediment loads incorporated in uneven patches across Arctic fast ice poses a challenge when designing observational studies of trace metals in sea ice. The scope of this thesis is on the study of trace metals in Alaskan Beaufort Sea fast ice environment. The study includes snow, sea ice and seawater under the ice. Analysis of dissolved (Mn, Fe, Cu and Zn) and particulate (Al, Mn, Fe, Cu and Zn) phases was carried out from 50 ice cores collected with a trace metal clean ice corer developed at the University of Alaska Fairbanks. The results of this study indicated that the ice corer developed at UAF was able to collect uncontaminated samples. Highly variable and elevated concentrations of particulate (> 0.2 μm) trace elements were observed due to the notable variability in the amount of sediment incorporated within ice cores, but surprisingly dissolved (< 0.2 μm) metal concentrations were relatively low and consistent. The observed low dissolved metal concentrations, along with low bulk salinity and low percent leachable particulate trace metal fractions, suggest that desalination removed reactive metals from the ice matrix prior to sampling. Spatial variability of dissolved and particulate trace metals was statistically analyzed and indicated generally negligible variability on the meter scale, but significant variability on the kilometer scale, for both size classes. These results emphasize that future studies of trace metals in sea ice should include temporal and spatial considerations.
    • Trace mineral reserves for reproduction and development in muskoxen

      Rombach, Emmajean Pearl (2001-12)
      In muskoxen (Ovibos moschatus), trace minerals required for reproduction and development are unknown. I described use of copper in pregnant muskoxen and concurrent accumulation of copper in fetuses. Utilization of copper was examined in neonates during early development and importance of milk as a source of copper was assessed. Additionally, I examined the effect of maternal copper supplementation during gestation on copper reserves acquired in-utero, and during lactation on mineral status of milk. During gestation, the fetus must acquire reserves of copper adequate to support early neonatal development because milk is a poor source of copper. The transition from milk to a forage-based diet may compromise immune function, growth, and survival of young as reserves established in-utero are likely depleted by that time. Maternal supplementation of copper during gestation and lactation provided little benefit to young, neither increasing mineral reserves in the fetus nor mineral content of milk. Nonetheless, supplementation during gestation may offset maternal costs.
    • Tracing Amino Acid Metabolism Of Harbor Seals (Phoca Vitulina) Using Stable Isotope Techniques

      Zhao, Liying; Schell, Donald M. (2002)
      Compound specific isotope techniques were used to trace amino acid metabolism in captive harbor seals (Phoca vitulina) through a two-year controlled feeding trial with either Pacific herring (Clupea pallasi ) or walleye pollock (Theragra chalcogramma). Techniques were developed for measuring carbon and nitrogen isotope ratios of individual amino acids. Carbon and nitrogen trophic enrichments in serum of captive harbor seals varied with the two fish diets, which might have resulted from the changes in metabolic pathway due to the differing dietary protein intake between herring and pollock. Data on serum free amino acid compositions also showed, from a different perspective, that changes in seal metabolism occurred in response to these different feeding regimes. Carbon and nitrogen isotopic composition of individual amino acids varied much more within an organism than across trophic levels, reflecting the distinct amino acid biosynthetic pathways. The similar patterns in relative amino acid carbon isotopic composition at different trophic levels indicated a conservative transfer of delta13C from primary producers to top predators. Nitrogen trophic enrichments in different amino acids were not uniform, depending upon the extent to which a given amino acid was transaminated or deaminated, with several essential amino acids showing lesser variations than most non-essential and branched-chain amino acids. The differences in amino acid isotope ratios among phocids from the North Pacific or Atlantic and their counterparts from the Antarctic reflected the geographic variations in isotopic composition of phytoplankton. The striking similarities in relative amino acid isotopic composition among phocids from the three distinct geographic locations indicated that phytoplankton worldwide had similar biosynthetic pathways during initial amino acid biosynthesis. This has important implications for using individual amino acid isotope ratios in studies of modern and prehistoric marine organisms. Amino acid metabolic pathways governed the varying patterns of 15N enrichments following 15N-labeled amino acid tracer infusions. Tracer experiments further confirmed that phenylalanine, threonine, lysine and probably histidine may be useful as relatively conservative natural biomarkers. This study provided new insight into mechanisms of isotopic trophic dynamics in food web studies and improved our understanding of seal protein metabolism.
    • Tracing sea ice algae into various benthic feeding types on the Chukchi Sea shelf

      Schollmeier, Tanja; Iken, Katrin; Wooller, Matthew; Hardy, Sarah (2018-12)
      Climate change in the Arctic is expected to have drastic effects on marine primary production sources by shifting ice-associated primary production to an overall greater contribution from pelagic primary production. This shift could influence the timing, amount, and quality of algal material reaching the benthos. We determined the contribution of sea ice particulate organic matter (iPOM) to benthic-feeding invertebrates by examining concentrations and stable carbon isotope values (expressed as δ¹³C values) of three FAs prominent in diatoms: 16:4(n-1), 16:1(n-7) and 20:5(n-3). Our underlying assumption was that diatoms make up the majority in sea ice algal communities compared with phytoplankton communities. According to the FA concentrations, subsurface deposit feeders consumed the most iPOM and suspension feeders the least. Conversely, there were little differences in δ¹³C values of FAs between deposit and suspension feeders, but the higher δ¹³C values of 16:1(n-7) in omnivores indicated greater consumption of iPOM. We suggest that omnivores accumulate the ice algal FA biomarker from their benthic prey, which in turn may feed on ice algae from a deposited sediment pool. The dissimilar results between FA concentrations and isotope values suggest that the FAs used here may not be sufficiently source-specific and that other unaccounted for production sources, such as bacteria, may also contribute to the FA pool. We propose that FA isotope values are a more indicative biomarker than FA concentrations, but there is a further need for more specific ice algal biomarkers to resolve the question of ice algal contributions to the Arctic benthic food web.