• Back to the future: Pacific walrus stress response and reproductive status in a changing Arctic

      Charapata, Patrick Maron; Horstmann, Larissa; Misarti, Nicole; Wooller, Matthew (2016-08)
      The Pacific walrus (Odobenus rosmarus divergens) is an iconic Arctic marine mammal that Alaska Natives rely on as a subsistence, economic, and cultural resource. A decrease in critical sea ice habitat and uncertain population numbers have led to walruses being listed as a candidate for the Endangered Species Act. However, there is no clear understanding of how walruses might be affected by climate change. The first objective of this study was to describe how bone steroid hormone concentrations relate to commonly used blubber and serum steroid hormone concentrations (i.e., cortisol, estradiol, progesterone and testosterone), because steroid hormones have not been extracted from marine mammal bone until now. Bone, blubber, and serum were collected from individual adult walruses (n = 34) harvested by Native Alaskan subsistence hunters during 2014 and 2015. Complete turnover of cortical bone in a walrus skeleton was estimated as ~33 years, approximately the lifetime of a walrus. Results showed bone and blubber steroid hormone concentrations were similar (P = 0.96, 0.51, 0.27 for cortisol, estradiol, and progesterone (males only), respectively), but not testosterone (males and females, P = 0.003) nor progesterone in blubber of female walruses (P = 0.007). Progesterone concentrations in males were significantly correlated between bone and blubber (R² = 0.51, P < 0.001). Estradiol measured in bone had high interannual variability (P < 0.001), indicating a shorter reservoir time in cortical bone compared with other hormones in this study, possibly due to local production of estradiol in walrus bone. Overall, bone serves as a long-term reservoir of steroid hormone concentrations compared with circulating serum concentrations. Progesterone measured in blubber can be compared with bone progesterone, but local production of estradiol in bone should be taken into account when interpreting these concentrations in cortical bone. The second objective of this study was to understand the physiological resiliency of walruses to the current warming in the Arctic. Steroid hormone concentrations were measured in walrus bone collected from archaeological (n = 38, > 200 calendar years before present (BP)), historical (n =135, 200 – 20 BP), and modern (n = 47, 2014 – 2015) time periods, but were also analyzed at a finer decadal (1830s – 2010s) scale. Walrus bone cortisol concentrations measured in modern-day walruses were similar to other time periods (P = 0.38, 0.07, for archaeological and historical time periods, respectively) indicating no increase in the stress response of walruses as a result of current sea ice conditions in the Arctic. Estradiol (females only), progesterone, and testosterone were significantly negatively correlated with walrus population estimates (P = 0.008, 0.003, <0.001, respectively). A negative correlation indicates that walrus population numbers are low when reproductive hormone concentrations are high, and population numbers are high, possibly at carrying capacity, when hormone concentrations are low. Data from the current decade (2014–2015) show that the current walrus population has lower reproductive hormone concentrations compared to times of rapid population increase. These data indicate the present-day walrus population may not be increasing, but is either experiencing low calf production and / or is near its carrying capacity. Overall, these data provide walrus management with insights into the physiological resiliency of walruses in response to arctic warming, and validate bone as a valuable tissue for monitoring long-term physiological changes in the walrus population.
    • Bacteria associated with paralytic shellfish toxin-producing strains of Anabaena circinalis

      Raudonis, Renee Alaine (2007-12)
      Paralytic shellfish toxins (PSTs) are produced by dinoflagellates and cyanobacteria. There is growing evidence that bacteria associated with dinoflagellates play a role in the production of PSTs, however, no studies have examined the type of bacteria associated with toxic cyanobacteria or the role these bacteria could play in PST-production or metabolism. Further, there are no known axenic cultures of PST-producing cyanobacteria, suggesting that cyanobacteria are dependent on one or more bacteria for growth/survival. The research reported here examined the bacterial community associated with six Australian freshwater cyanobacterial strains of Anabaena circinalis obtained from the CSIRO, three toxic and three non-toxic. The goal was to identify bacteria that could be essential for cyanobacterial growth/survival and/or PST production/metabolism. Confirmation of cyanobacterial species identification was confirmed by molecular techniques; one species was found to be more closely related to Anabaena flos-aquae. PST-production by the three toxic strains was confirmed using HPLC. Bacterial communities associated with the cyanobacteria were dominated by the [alpha]-Proteobacteria, of which the Rhizobiales group was dominant. Two bacterial ribotypes were associated with only the toxic cyanobacteria, and could be important in PST-remineralization.
    • Barents Sea hydrographic variability (1975-1991)

      Zimmermann, Sarah Lukens (2003-12)
      Barents Sea temperature and salinity anomalies and their connection to the Arctic Oscillation (AO) are analyzed using a 16-year time-series of hydrographic data (1975-1991). Seasonal and inter-annual variations are investigated along two sections spanning the meridional and zonal length of the Barents Sea over two depth layers, 0 to 50m and 50 to 200m. Depending on location, mean seasonal differences in the deeper layer are as large as 3°C in temperature and 0.2 in salinity, whereas the upper layer differences are 6°C and 1.4. Inter-annual anomalies are 0.6°C and 0.07 in the deeper layer and 0.8⁰C and 1.2 in the upper layer. Temperature and salinity anomalies' leading EOFs explain 49% and 34% of the total variance, and are in-phase from 1975-1985 but out-of-phase for 1985-1991. Examination of the surface heat-flux suggests the temperature anomaly is advective before 1985 and locally formed after 1985. This is supported by the temperature anomaly's changing propagation pattern through the Barents Sea after 1985. The salinity anomaly's source appears to be advective throughout the period. The AO correlates with the temperature EOF suggesting the AO's influence on the temperature anomaly is stronger over the Norwegian Sea before 1985 and stronger over the Barents Sea after 1985.
    • Bathymetric and spatial distribution of echinoderms on seamounts in the Gulf of Alaska

      Underwood, Danielle Parker (2006-12)
      The bathymetric and spatial distribution of echinoderms was examined on five seamounts in the Kodiak-Bowie seamount chain in the northern Gulf of Alaska from video transects of 200 or 500 m length, conducted at approximately 700, 1700 and 2700 m depths with the DSV Alvin in August, 2004. Temperature and salinity varied significantly with depth, but not between seamounts; an oxygen minimum zone encompassed the shallowest depth sampled. Holothuroid (Pannychia and Psolus) and asteroid density for the shallower depth category was 19.94·100 m⁻² and 2.07·100 m⁻², significantly higher than at the deeper depths. Asteroid density generally decreased northwesterly along the seamount chain. Density of three ophiuroid genera (Asteronyx, Amphigyptis, and Ophiomoeris) was 139.6·100 m⁻² on Dickens Seamount, and was significantly less on the other three seamounts to a low of 31.19·100 m⁻² on Pratt Seamount. Ophiuroid density was significantly higher at the intermediate depth (141.07·100 m⁻²), and lower at the other two depths. Density of Pentametrocrinus and Guillecrinus crinoids was not significantly affected by seamount or depth, but was highest (3.15·100 mm⁻²) at the deepest depths. No echinoids were found on transects, but were observed on three of the seamounts. Many brittle stars and asteroids were found associated with paragorgid and primnoid corals.
    • Bathymetry of Alaskan arctic lakes: a key to resource inventory with remote-sensing methods

      Mellor, Jack C. (1982-05)
      Water depth is a major factor in predicting resources associated with tens-of-thousands of uninventoried Alaskan arctic lakes. Lakes were studied for physical, chemical, and biological resources related to water depth in 3 specific areas along a north/south transect extending from Pt. Barrow on the Arctic Ocean to the foothills of the Brooks Range. Side-Looking Airborne Radar (SLAR) imagery was acquired over the same study transect to investigate its application for determining lake depth. Ice thicknesses, necessary for the interpretation of depth contours from SLAR imagery, were measured along with other parameters in the study lakes throughout the winter 1978-79. This ice-thickness data and sequential SLAR images are used to illustrate a method of contouring water depths in arctic lakes. This is based on changes in intensity of SLAR signal return which define the zone at which ice cover contacts the bottom. This intensity is a function of physical and dielectric properties of the snow, ice, water, bottom substrates, and ice inclusions within these lakes. A computer program was developed to manipulate Landsat satellite digital data and compile a master file of lakes and their computer-calculated surface features (i.e. area, perimeter, crenulation, and centroid). The master file uniquely identifies each computer catalogued lake by latitude and longitude and stores the calculated features in a data base that can be retrieved for a specified geographic ABSTRACT area. Each lake record also provides storage space for resource data collected outside the computer generated data. The application of these remote-sensing tools and the knowledge of aquatic resources associated with bathymetry add to our ability for regional inventory, classification, and management of arctic lake resources.
    • Benthic community development in Boca de Quadra, Alaska

      Winiecki, Carol Irene (1986-05)
      The purpose of this experiment was to find ways of evaluating the community development in Boca de Quadra, a fjord in southeast Alaska, after a severe physical disturbance. Containers of defaunated sediment were used near the head of the fjord to simulate the benthic habitat after such a disturbance. Important features of community development were described, potential indicator taxa were selected, and the extent of community development was examined. Seasonal variations tended to mask the developmental trends. However, samples collected during the same season, but representing various lengths of colonization, allowed developmental trends to be observed in faunal composition, numbers of taxa, density, biomass, and diversity. Maldanidae, Nematoda, Lumbrineris luti. Leitoscoloplos pugettensis, Pholoe minuta. and Spionidae are potential indicators of community maturity.
    • Biochemical and microbiological assessments of dried Alaska pink salmon, red salmon and Pacific cod heads

      Biceroglu, Huseyin; Smiley, Scott; Crapo, Charles; Bechtel, Peter J. (2012-05)
      Fish heads are generally considered as unsuitable byproducts for human consumption in the United States. The initial objective was to compare the moisture content and water activity levels on dried pink salmon (Oncorhynchus gorbuscha) and dried red salmon (O. nerka) using different temperature and time integration. The secondary objective was to compare shelf life characteristics, rancidity and mold growth, between dried pink dried salmon and dried Pacific cod (Gadus macrocephalus) heads stored for up to 180 days at the ambient temperature (21°C) for East African seafood markets. The third objective was to assess the antioxidant effects for frozen and dried pink salmon heads stored for up to 60 days. In a preliminary experiment, dried red salmon heads were found unsuitable due to the water activity levels above 0.6. The critical moisture contents were detected around 10% for pink salmon heads and were around 15% for Pacific cod heads to reduce water activity levels below 0.6 in these products. The applicable drying temperatures of 50°C lasting over 50 hours for pink salmon heads and 50°C for over 24 hours followed by 30°C for over 24 hours for Pacific cod heads were found optimal. Dried Pacific cod heads showed shelf stability as a potential dried seafood product. Frozen pink salmon heads had 60 days shelf life, while heads with antioxidant glazing retarded oxidation levels (p <0.05). The antioxidant treatment in dried pink salmon heads kept oxidation levels lower than the acceptable limit up to 60 days. This study provided essential information to improve the utilization of these Alaskan seafood byproducts.
    • Bioenergetic and economic impacts of humpback whale depredation at salmon hatchery release sites

      Chenoweth, Ellen M.; Atkinson, Shannon; McPhee, Megan; Criddle, Keith; Friedlaender, Ari; Heintz, Ron; Straley, Janice (2018-08)
      Since 2008, humpback whales have been documented depredating hatchery-produced juvenile salmon, a novel prey, at points of their release in Southeast Alaska. The objectives of this dissertation are to determine the spatial distribution, seasonal distribution, and frequency of humpback whale foraging at release sites, determine whether whale presence is affecting the economic productivity of hatchery operations, and compare the bioenergetic benefits for whales feeding on juvenile salmon at hatchery release sites relative to typical prey. Five hatchery release sites were monitored over six years during the spring release season for whale presence/absence, numbers, and behaviors. Linear models were used to determine that for coho salmon, cohorts with frequent humpback whale presence had lower marine survival than cohorts with less or no humpback whale presence, but this was not seen for chum or Chinook salmon. Over six years, these sites lost an estimated 23% of revenue from coho salmon totaling almost a million dollars per year in addition to increased rearing costs to mitigate whale predation. A process model was developed to compare the net energy gain for humpback whales foraging on krill, herring and juvenile salmon. Whales were found to feed profitably on krill and chum salmon where they occurred in dense enough distributions and on herring when large coordinated groups impeded the escape of prey. Coho salmon typically distributed too diffusely for humpback whales to recuperate the full energetic costs of engulfment, indicating that behaviors such as bubble net feeding may be essential for increasing prey aggregation to an energetically profitable level, or humpback whales may be feeding to mitigate energetic losses. As intraspecific competition increases due to recovery and or changes to prey resources, generalist humpback whales may expand feeding to exploit new and less profitable prey resources.
    • Biogeochemical tracers of change in Pacific walruses past and present

      Clark, Casey; Horstmann, Lara; Misarti, Nicole; Konar, Brenda; Severin, Ken; Lemons, Patrick (2019-05)
      Reduced sea ice and projected food web shifts associated with warming of the Arctic have raised concerns about the future of Arctic species. Pacific walruses (Odobenus rosmarus divergens) use sea ice as a platform for molting, giving birth, and resting between foraging bouts. Exactly how sea ice loss will affect walruses is difficult to predict, due to a lack of information about regional ecosystems and their responses to climate change. The objectives of the research in this dissertation were to 1) examine how walrus diet changed in response to shifting sea ice conditions over the last 4,000 years, with the goal of generating predictions about how current and future ice loss may affect the walrus population; 2) make it easier to directly compare the results of retrospective and contemporary stable isotope studies of walruses; and 3) generate new tools to assist wildlife managers in monitoring the walrus population in an uncertain future. Stable carbon and nitrogen isotope ratios of walrus bone collagen indicated that diet was similar during previous intervals of high and low sea ice; however, diet variability among individual walruses was greater when sea ice cover was low, suggesting decreased abundance of preferred mollusk prey. Modern walrus diet was different from both previous high and low ice intervals, meaning that food webs in the Arctic are still in a state of flux, or that recent changes are novel within the last 4,000 years. Tissue-specific stable isotope discrimination factors were generated for walrus muscle, liver, skin, and bone collagen to improve comparisons between retrospective and contemporary studies of walrus diet. Additionally, lipid normalization models were parameterized for walrus skin and muscle, thereby making future walrus stable isotope research more feasible by reducing analytical costs and allowing the use of non-lethal sample collection. Finally, a novel technique for estimating the age at onset of reproductive maturity using concentrations of zinc and lead in the teeth of female walruses was established. This new approach has the potential to become a powerful tool for monitoring the walrus population and may be applicable to other species. Use of this technique on archived specimens may make it possible to examine changes in wildlife population dynamics across thousands of years.
    • Biogeochemistry of a glaciated fjord ecosystem: Glacier Bay National Park, Alaska

      Reisdorph, Stacey; Weingartner, Thomas; Mathis, Jeremy; Hood, Eran; Danielson, Seth; Aguilar-Islas, Ana (2015-05)
      The burning of fossil fuels, coupled with land use and deforestation practices, has resulted in CO₂ being emitted into the atmosphere. As much as one third of the anthropogenic, or man-made, CO₂ that ends up in the atmosphere is absorbed by the oceans and has led to increases in marine dissolved inorganic carbon (DIC) concentrations and a decrease in ocean pH, a process referred to as ocean acidification (OA). Increased concentrations of DIC can reduce saturation states (Ω) with respect to biologically important calcium carbonate minerals, such as aragonite. However, CO₂ may not be the only factor in seasonal changes to calcium carbonate saturation states. With this project I was interested in understanding how glacial runoff impacts the seasonal changes to the marine biogeochemistry in a glaciated fjord. In addition to CO₂, glacial meltwater is low in alkalinity (TA) and may impact the seasonal biogeochemistry of the marine system, as well as how it influences the duration, extent, and severity of OA events in an Alaskan glacial fjord, Glacier Bay National Park (GLBA). Through this study, I found that glacial runoff heavily impacts aragonite saturation states, with the main drivers of Ω (DIC and TA) varying seasonally. In GLBA low Ω values were well correlated with the timing of maximum glacial discharge events and most prominent within the two regions where glacial discharge was highest. The influence of glaciers is not limited to just TA as runoff is also low in macronutrients due to a lack of leaching from the soil and rocky streambeds. This has the potential to greatly impact the efficiency and structure of the marine food web within GLBA, the lowest level of which can be estimated using net community production (NCP). Changes within the lowest level of the food web, as a result of seasonal OA events, may lead to bottom-up effects throughout the food web, though this project focused only on production and respiration signals within the lowest level. We estimated regional NCP values for each sampling season and found the highest NCP rates (~54 to ~81 mmoles C m⁻² d⁻¹) between the summer and fall of 2011, with the most marine influenced lower part of the bay experiencing the greatest production. As the climate continues to warm, further glacial volume loss will likely lead to additional modifications in the carbon biogeochemistry of GLBA. Understanding the dynamics that drive seasonal changes in Ω, NCP, and the associated air-sea CO₂ fluxes within glacially influenced Alaskan fjords can provide insights into how deglaciation may affect carbon budgets and production in similar fjords worldwide.
    • Biophysical factors associated with the marine growth and survival of Auke Creek, Alaska coho salmon (Oncorhynchus kisutch)

      Robins, Joshua Benjamin (2006-12)
      Correlation and stepwise regression analyses were used to investigate relationships between growth in four distinct marine habitats, marine survival, and biophysical indices for Auke Creek coho salmon, a coho salmon population in Southeast Alaska. Early marine growth of males and females were positively correlated, but neither was correlated with early marine growth of jacks. Regional biophysical indices had significant effects on early marine growth of jack, but not on early marine growth of adult coho salmon. Sea surface temperature and number of hatchery pink and churn salmon juveniles released had negative and positive effects on growth in strait habitat, respectively. Hatchery pink and churn salmon abundance and pink salmon catch in Northern Southeast Alaska were negatively related to the growth of Auke Creek coho salmon in the late ocean phase. The average length-at-return of males, but not females, was negatively related to the abundance of hatchery pink and chum salmon. Female and male size-at-return were positively correlated (r = 0.68) but within-year variation was less for females, indicating possible sex-specific differences in adult size requirements associated with reproductive success. Adult survival and jack return rate were significantly related to early marine growth of adults and jacks, respectively, indicating size-selective mortality. Hatchery pink and churn salmon abundance had positive effects on adult survival and jack return rate.
    • Biotic and abiotic influences on the use of Arctic lakes by fish and loons

      Haynes, Trevor B.; Lindberg, Mark; Rosenberger, Amanda; Lopez, Andrés; Titus, Kimberly (2014-12)
      The particularly severe effects of climate change anticipated in the Arctic, accompanied by ongoing anthropogenic activities, necessitate proactive and knowledge-based management of the region's aquatic ecosystems. However, the paucity of information on the Arctic's aquatic environments hinders strategic or spatially-explicit management. In this dissertation, I examine the habitat use of poorly studied taxa of the Arctic Coastal Plain (ACP) of Alaska, including freshwater fishes and yellow-billed loons (Gavia adamsii). Distribution studies can be biased by false absences; therefore, I began by determining the detection probabilities of six fish species common to Arctic lakes for five gear types (Chapter 2). Variation in gear- and species-specific detection probability was considerable, suggesting a multi-method approach may be most effective for whole-assemblage sampling. Adjusting for detection probability, I then examine how occupancy probabilities of the six fish species were related to lake and landscape scale covariates (Chapter 3). Three large-bodied salmonid species were influenced by factors associated with the probability of fish colonizing lakes, including whether the lakes had a stream connection. Models for small-bodied fish indicated different strategies for persistence among species. Ninespine stickleback (Pungitius pungitius) were widespread and captured in lakes that freeze to the bottom, suggesting rapid dispersal after spring freshet (when snow and ice had melted rapidly and caused widespread flooding) and colonization of sink habitats. In contrast, Alaska blackfish (Dallia pectoralis) distributions reflect tolerance to harsh conditions, while the slimy sculpin's (Cottus cognatus) was indicative of its marine origin. Based on these patterns, I propose a model of primary controls on the distribution of fishes in ACP lakes. Severe winter conditions limit occupancy through extinction events, while lake occupancy in spring and summer is driven by directional migration (large-bodied species) and undirected dispersal (small-bodied species). To provide insight to the relevance of species-specific distributions of prey fish to yellow-billed loons (Gavia adamsii), I investigated loon diet on their breeding grounds using quantitative fatty acid signature analysis (Chapter 4). Tissues were collected from 26 yellow-billed loons (shortly after they had moved from coastal staging areas), nine fish species and two invertebrate groups. Results suggest that yellow-billed loons are eating high proportions of Alaska blackfish, broad whitefish (Coregonus nasus) and three-spined stickleback (Gasterosteus aculeatus). The prominence of blackfish in diets highlights the importance of this species' tolerance to winter conditions that permits its widespread availability during the early stages of loon nesting. Broad whitefish and three-spined stickleback are more likely to be encountered in coastal regions at this time, and their importance may reflect pre-nesting period diet, when loons are staging in coastal and brackish waters before lakes are ice free. Finally, I use the prior chapters to inform an investigation into lake occupancy dynamics of nesting yellowbilled loons and loon chicks (Chapter 5). From a total of four years of data (collected over nine years for nests and seven years for chicks), I examine landscape features that influence the distribution and breeding success of breeding loons on ACP lakes (>7 ha in area), including landscape and lake features, and fish prey occupancy. Over this time, nesting yellow-billed loons exhibited a relatively low (< 30%), but stable to increasing, lake occupancy. Local extinction and colonization rates were also relatively stable, suggesting the nesting population in this region may be near equilibrium. A decreasing rate of change in chick occupancy associated with concomitant increases in nesting occupancy implies density-dependence in chick production. The occupancy probability of a prey fish, least cisco (Coregonus sardinella), had a positive influence on the probability of colonization of unoccupied lakes by nesting loons. I confirm that lake size and lake depth were not only positively associated with nesting occupancy, but also with chick production. Large lakes had occupancy probabilities near one for nesting loons and chicks; this, along with the near equilibrium in breeding loon occupancy and the relative rarity of these large lakes over the landscape, suggests breeding habitat is limiting loon populations in this part of their range. Given the lack of data from the ACP on fish distributions and yellow-billed loons, my findings inform current management practices and provide foundation for future research.
    • Blasting Bridges And Culverts: Water Overpressure And Vibration Effects On Fish And Habitat

      Dunlap, Kristen N.; Smoker, William; Timothy, Jackie; Kelley, John; Quinn, Terrance II (2009)
      Water overpressures and ground vibrations from blasting may injure or kill salmonid fish in streams and embryos in streambeds. Explosives are used to remove failing structures in remote areas of the Tongass National Forest that impair watershed function. The State of Alaska Department of Fish and Game standards limit blast induced water overpressures to 2.7 lb/in 2 (18.6 kPa) and streambed vibrations to 0.5 in/s (13 mm/s) when embryos are present. Researchers, however, have reported salmonid mortality from pressures only as low as 12.3 and 19.3 lbs/in2 (85 and 133 kPa) and embryo mortality from vibrations as low as 5.75 in/s (146 mm/s). I recorded in-stream overpressures and streambed vibrations with hydrophones and geophones at various distances from log bridge, log culvert, and metal culvert blasts. Peak water pressures (lb/in2) were directly related to cube-root scaled distances with an attenuation rate of -1.51. Peak particle velocities in gravel were directly related to square-root scaled distances (SRSD, ft/lb 1/2) with an attenuation rate of -0.75. Water pressures were less than 7.1 lb/in2 (49.0 kPa) in all but one blast, and streambed vibrations did not exceed 5.5 in/s in gravel streambeds. State standards should be revised to reflect reported mortality and these observations of blasts in streams.
    • Blubber and beyond: the role of lipids in thermoregulation and energy reserves of phocid seals

      Pearson, Linnea E.; Burns, Jennifer M.; Horstmann-Dehn, Larissa-A.; Pfeiffer, David C.; Mellish, JoAnn E.; Buck, C. Loren (2015-08)
      Phocid seals rely on lipids in the form of a blubber layer as insulation and lipids as energy sources in blubber and muscle. The amount and lipid composition of blubber and other lipid stores vary throughout life within and among species of phocid seals. I hypothesized that this variation in regulation, allocation, and interactions among lipid stores is influenced by species, ontogeny, and tissue-specific thermal regimes in polar phocids: harp (Pagophilus groenlandicus), hooded (Cystophora cristata), and Weddell (Leptonychotes weddellii) seals. I investigated the thermoregulatory strategy of neonatal harp, hooded, and Weddell seals, and throughout the transition to an aquatic environment in harp seals. All three species had similar thermal resistance, though it was achieved differently using either lanugo or blubber. While there was variation in the main thermoregulatory strategy among species, no species possessed all thermal adaptations of adults. Harp and Weddell seals had higher surface area to volume ratios (SA:V), thus higher potential heat loss, though compensatory mechanisms for heat production were different between species. Harp seals were the only species with the potential for nonshivering thermogenesis (NST) in brown adipose tissue (BAT), whereas Weddell seals had the highest potential for shivering thermogenesis (ST) in their skeletal muscle. Hooded seals relied on blubber, and had a significantly lower SA:V than the other two species. As harp seal pups develop, their potential for NST declines and they shift to a reliance on blubber for insulation. By late weaning, harp seal pups have similar insulative capabilities as adults, and can likely meet the thermoregulatory challenges associated with living in water. In neonatal and young seals that have little blubber, other lipid stores such as BAT and skeletal muscle lipids provide heat-generating mechanisms (NST or ST) to offset potentially high rates of heat loss. The potential for NST declines with age, as the blubber layer develops in harp seals, and weaned pups look to have similar insulative capabilities as adults. While phocid adults rely on blubber for insulation and maintain a thermal gradient across the tissue, otariids (fur seals and sea lions) instead maintain an external gradient across a thick fur layer. This has implications for the underlying lipid composition of blubber, as the fatty acids (FA) that make up this lipid respond differently to temperature. In phocid blubber, latitude (a proxy for environmental temperature) had a positive correlation with the proportion of polyunsaturated fatty acids, but a negative correlation with saturated fatty acids. In otariids, these trends were reversed. This suggests interactions between blubber and the ambient environment play a role in the overall relative proportions of FA classes in blubber. Unlike in blubber, the FA class composition of harp, hooded, and Weddell seal skeletal muscle was similar among species. In adult female Weddell seals, the relative proportions of individual FA in blubber and muscle were significantly different between tissues; these differences persisted across seasons, and were independent of female reproductive state. It appears that the FA in blubber and muscle reflect the tissues' roles within the body. Blubber contained a greater proportion of monounsaturated FA, which remain fluid at lower temperatures, while the muscle contains a larger proportion of SFA, which produce the greatest amounts of ATP per mole oxidized to support metabolism. In adult phocids, the FA composition of the blubber layer appears to be influenced by environmental interactions with latitude (temperature), in accordance with the location of and steepness of the thermal gradient through the blubber layer. Finally, environment looks to have little influence on the FA stores in skeletal muscle, and seasonally persistent tissue differences between blubber and muscle highlight how lipid is dynamically modulated within the body of phocid seals. How and what lipids are allocated to blubber is a mixture of abiotic and biotic cues throughout life, linked to thermodynamics, ambient environment, and energy dynamics.
    • Body composition (carbon, nitrogen and calories) and energetics of immature walleye pollock, Theragra chalcogramma (Pallas), in the southeast Bering Sea

      Harris, Robert K. (1985-05)
      The body composition (carbon, nitrogen and calories) of Bering Sea and Resurrection Bay (Alaska) immature walleye pollock (9-360 g wet weight) were related to dry weight and Fulton's condition factor index by regression models. The condition factor was a better predictor of body composition than dry weight. As condition improved from a minimum starvation level of 0.42 to a maximum of 1.16, body caloric, percent carbon, and the carbon-nitrogen ratio increased, while percent nitrogen and percent ash decreased. The body composition measurements allowed energy budget terms (assimilation coefficient, growth, and metabolism) to be expressed in common units. The assimilation coefficient and growth terms were estimated from literature sources. Oxygen consumption measurements at 3-10°C yielded the metabolic term. The daily food requirement for 0-3 year old walleye pollock, at their annual average Bering Sea habitat temperature of 3.8°C, was 1.0 - 1.5% of the body weight.
    • Breeding performance of kittiwakes and murres in relation to oceanographic and meteorologic conditions across the shelf of the southeastern Bering Sea

      Lloyd, Denby S. (1985-12)
      Contrary to expected results, black-legged and red-legged kittiwakes on St. George Island exhibited more variability in annual breeding performance than black-legged kittiwakes at Cape Peirce. Thick-billed and common murres at St. George also showed more annual variability than common murres at Cape Peirce. Kittiwakes at St. George exhibited improved breeding performance during years with colder water temperatures and lower summer wind speeds. Correlations between breeding performance in kittiwakes and murres and environmental conditions at Cape Peirce were inconclusive. A general decline in the annual breeding success of kittiwakes and murres at St. George between 1976 and 1984 coincided with reduced abundance of juvenile walleye pollock. Consistently low breeding success of kittiwakes and murres at Cape Peirce varied little among six years observed between 1970 and 1984. These results challenge previous considerations of pelagic food webs on the outer shelf as being more stable than those in the coastal domain.
    • Carbon and nitrogen assimilation in the Bering Sea clams Nuculana radiata and Macoma moesta

      Weems, Jared; Iken, Katrin; Gradinger, Rolf; Wooller, Matthew (Elsevier, 2012-06)
      We analyzed bulk carbon and nitrogen stable isotope values (delta C-13 and delta N-15) of the benthic clams Nuculana radiata and Macoma moesta from the Bering Sea during controlled feeding experiments (spring of 2009 and 2010) using isotopically labeled sea ice algae. The aim was to determine the ability of these clam species to assimilate carbon and nitrogen from sea ice algae. Specimens were collected in the Bering Sea and placed into jars without sediment (2009, N. radiata only) or into natural sediment cores (2010, both species). The clams were offered isotopically enriched (both C and N) or non-enriched algal feeds for time periods of 42 (2009) and 18 d (2010). Isotopic assimilation rates for carbon and nitrogen were calculated using the change in the isotope ratios of the clams over the experimental time. N. radiata in the jar experiments had slow isotopic assimilation rates (0.01 to 0.23 parts per thousand d(-1)), with solvent-extractable organic matter/lipids taking up both of the isotope markers fastest and muscle tissue the slowest. Lipids may thus be particularly suitable to track the immediate ingestion of sea ice algal production in benthic consumers. M. moesta showed 30% higher isotopic assimilation compared to N. radiata in sediment cores, likely reflecting the different feeding behaviors of these two species. Based on our results, N. radiata is likely better able to utilize food sources buried in the sediment and may be more competitive over the sediment surface feeding M. moesta under conditions of reduced ice algal production in the northern Bering Sea. (C) 2012 Elsevier B.V. All rights reserved.
    • CARBON AND NITROGEN ASSIMILATION IN THE CLAMS NUCULANA RADIATA AND MACOMA MOESTA FROM THE BERING SEA

      Weems, Jared; Iken, Katrin; Gradinger, Rolf; Wooller, Matthew (University of Alaska Fairbanks, 2011-08)
      The predicted climate-induced reduction in sea ice presence in the Bering Sea could impact benthic trophic interactions; however, species-specific consumer dependence on ice algal production is largely unknown. My objective was to track feeding in the benthic clams, Nuculana radiata and Macoma moesta, using stable carbon and nitrogen isotopes. Nuculana radiata had slow isotopic assimilation rates, with lipids taking up isotope markers fastest and muscle tissue the slowest. Lipids may thus be particularly suitable to track the immediate ingestion of sea ice algal export in benthic consumers. When isotopically enriched food was added to natural sediment cores, N. radiata assimilated 60% less of the isotope markers than when feeding on algal food in isolation. Possibly, this difference is related to the ingestion of other, naturally present food sources in the sediment. Macoma moesta showed 30% higher isotopic assimilation compared to N. radiata in sediment cores. I suggest that differing feeding behaviors between the species provide differential access to the sedimented algal food. Based on these results, N. radiata is likely better able to utilize food sources buried in the sediment and may be more competitive over M. moesta under conditions of reduced ice algal production in the northern Bering Sea.
    • Carbon biogeochemistry of the eastern Bering Sea shelf

      Cross, Jessica; Mathis, Jeremy; Feely, Richard; Stockwell, Dean; Weingartner, Thomas; Whitledge, Terry (2013-12)
      The uptake of anthropogenic carbon dioxide (CO₂) has caused perturbations to marine biogeochemistry in recent years, including decreasing ocean pH and carbonate mineral saturation states (Ω). Collectively termed ocean acidification (OA), these conditions hinder the growth of calcium carbonate shells and effectively reduce habitat for some marine calcifiers. Given that the Bering Sea is one of the world's most productive marine ecosystems and supports both commercial fishing industries and subsistence communities, it is integral to understand its susceptibility to OA. Here, new observations of the organic and inorganic carbon systems are used to identify mechanisms leading to CO₂ accumulation and sub-regional enhancement of vulnerability to OA processes. Chapter 1 describes the state of knowledge of OA in this area, highlighting two regions where low Ω conditions are consistently observed: near the coast, and over the northern shelf. Chapter 2 describes net heterotrophic processes near the coast, in conjunction with low bottom water Ω. Chapter 3 examines this heterotrophy in more detail, showing that focused deposition of organic matter and its subsequent respiration. Chapters 4 and 5 focus on very low Ω values observed over the northern shelf. In combination with natural respiration processes, anthropogenic CO₂ was shown to cause low Ω and seasonal dissolution of carbonate minerals in Chapter 4. Chapter 5 illustrates how sea ice cover inhibits the flux of CO₂ from the surface ocean to the atmosphere, which raises the inventory of CO₂ in the water column. These results are synthesized in Chapter 6. Low-Ω conditions and areas of carbonate mineral dissolution will continue to expand as anthropogenic CO₂ accumulates in shelf waters in the coming decades, further reducing viable habitat for key calcifiers. Model projections of future surface water conditions indicate that average Ω over the Bering Sea shelf will drop below the observed natural variability by 2100, with average conditions favoring carbonate mineral dissolution in surface waters by 2150. Presently, episodic events will cause regions of the Bering Sea to be undersaturated in Ω, which could have significant and cascading impacts throughout the Pacific-Arctic region.