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  • Evaluation of prey composition and nutritional value of diets of free-ranging harbor seals (Phoca vitulina) from Tugidak Island

    Geiger, Gretchen L.; Atkinson, Shannon; Carpenter, James; Horstmann-Dehn, Larissa; Wynne, Kate (2012-12)
    Changes in climate can cause shifts in ecosystem structure that can affect quantity or quality of prey available to predator populations. Due to sex or age-specific behaviors of predators, certain classes within a population may be more severely impacted by changes in their diet. This study evaluated prey composition and nutritional value of summer diets of harbor seals (Phoca vitulina richardii) from Tugidak Island, Alaska from 2001-2009. The MIXIT-WIN program was used to estimate the nutritional value of average harbor seal diets. Changes in relative abundance of certain prey species were correlated to sea surface temperature anomalies. Despite changes in prey composition, the nutritional value of the average harbor seal diet did not change. Fecal corticosteroid metabolite profiles were analyzed to identify age and sex of individual harbor seals from scats. Profiles obtained from a known adult male harbor seal could be differentiated from those of known adult female and juvenile male seals. Similar profiles were observed in unknown age and sex samples. Even though diet diversity differed between these groups, the nutritional quality of consumed diets was not significantly different. Tugidak Island harbor seals have flexible diets allowing them to capitalize on available prey to maintain their nutritional intake.
  • Energetics of arctic Alaskan fishes: carbon isotope evidence

    Ziemann, Paul J. (1986-12)
    The natural abundance of carbon isotopes were used to investigate the energy requirements of arctic aquatic consumer organisms. A mathematical model was developed that describes the relationship between the rate of consumer isotope turnover rates of growth and metabolism, and the utility of the model for calculating energy requirements from seasonal changes in consumer isotopic composition was demonstrated in laboratory experiments and with field data. The energy requirements of anadromous fishes, which were the major consumers studied, could not be determined using the isotopic data. Instead, the requirements were calculated using biochemical data and rates of growth and oxygen consumption, and were about 2.6-6.0 kcal day⁻¹ in the summer and 0.4-1.2 kcal day⁻¹ in the winter. Seasonal changes in lipid and protein contents indicate that anadromous fishes cannot find enough food during the winter to supply their energy requirements, and that about 50% of the energy needed comes from the metabolism of tissues accumulated during the summer. The relative importances of marine and freshwater food webs in supplying the energy requirements were determined by comparing the seasonal isotopic components of anadromous fishes to the isotopic compositions of fish that are permanent residents in each environment. It appears that anadromous fishes that overwinter in the Coleville River (the largest river on the Alaska North Slope) depend almost entirely on the marine environment for their energy, whereas those that overwinter in Canada's Mackenzie River rely on both marine and freshwater habitats.
  • The feeding, movement, and growth of pink salmon, Oncorhynchus gorbuscha, fry released from a hatchery in Prince William Sound, Alaska

    Urquhart, David Lindsay (1979-12)
    As part of a study that investigated the ability of Prince William Sound to support large numbers of juvenile salmon, the movements, feeding, and growth of pink salmon, Oncorhynchus gorbuscha, fry released in the springs of 1977 and 1978 from the Port San Juan hatchery, are described. Fry were released in Sawmill Bay but preferred the waters of adjacent Elrington Passage where they remained for up to two months. Nursery areas in the Passage established by the fry in 1977 were not occupied to the same degree in 1978. Fry fed initially on epibenthic harpacticoid copepods but soon switched to feeding on calanoid copepods. Fry growth rates and diet are comparable with results of other studies. Fry behavior affected sampling and may account for between-year differences detected in growth. Weather, food abundance, and the condition of out-migrants may also account for between-year differences in fry behavior and growth.
  • Comparing the nutritional quality of Steller sea lion (Eumetopias jubatus) diets

    Bando, Monica Kaho Herkules (2002-12)
    Though the primary cause(s) of the Steller sea lion decline remains unknown, one hypothesis is nutritional stress, possibly the result of climatic regime shifts reducing prey availability and/or quality. Researchers at the Alaska SeaLife Center formulated three feeding regimes representative of Steller sea lion diets: prior to and during their population decline and from a stable population. The purpose of this project was to compare the nutritional quality of these diets using proximate composition and bomb calorimetry. The pre-decline and stable diets are composed of more high-fat prey, like herring, with resulting energy densities being significantly higher than the decline diet, comprising more low-fat prey, like octopus. Assumining the feeding regimes analyzed represent Steller sea lion diets prior to and during their population decline and in stable populations, results from this study are consistent with the possibility that nutritional stress is a cause of the Steller sea lion decline.
  • 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.
  • 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.
  • Phosphorus metabolism of several aquatic microorganisms

    Lang, Douglas; Brown, E. J. (1980-12)
    Several taxonomically diverse aquatic microplankton were described growing at phosphorus (P) concentrations that limit growth in many natural aquatic systems. Because natural aquatic systems are subject to periodic fluctuations in P levels, both steady-state (via continuous culture) and transient (via batch culture) growth were described. Complete growth kinetic descriptions of Synechococcus Nageli (strain A) and Scenedesmus quadricauda were used to predict the relative competitive abilities of these species when P was the growth-limiting nutrient. These descriptions, coupled to their morphological characteristics, were used to construct partial physiological profiles for each organism. The profiles indicate that S. Nageli (strain A) (a small unicellular blue-green alga) is better suited for growth in P-limited oligotrophic niches than is S. quadricauda (a green alga). However, results from kinetic experiments with these and several other microplankton, show that such physiological profiles are not necessarily indicative of profiles for taxonomically related species.
  • A synopsis of the marine prosobranch gastropod and bivalve mollusks in Alaskan waters

    Foster, Nora Rakestraw (1979-12)
    This study presents information on the taxonomv and distribution of the marine prosobranch gastropod and bivalve mollusks from the waters surrounding Alaska. Three hundred fifty-two species of prosobranch gastropods and 202 species of bivalves are reported from these waters. Over 3,000 lots of specimens, representing 330 species and literature sources form the basis of this study. References, synonymy, geographic and bathymetric ranges are provided for each species. Characteristics used to identify the species of 66 genera are presented in tabular form. The greatest number of species is reported from the southern Bering Sea, the fewest from the Beaufort Sea. Most of the species have wide ranges in the eastern or western Pacific. New collecting records reported here extend the known ranges of 27 species. Eight species were previously unknown from Alaskan waters.
  • The role of stratification in the spring ice edge bloom in the Bering Sea: a numerical model

    Freed, Martin (1984-09)
    Marginal ice edge zones are unique frontal systems with air-ice-sea interfaces. Phytoplankton blooms which occur along the edge of some melting ice packs in the spring, appear to be related to melt water driven density stratification. In this thesis a numerical model of a marginal ice edge zone is constructed. The wind driven circulation and spring phytoplankton bloom at the Bering Sea ice edge are simulated as functions of air-ice-sea-biology interaction. It was found that as long as the ice was allowed to melt, blooms occur regardless of wind direction. However, because of the compactness dependent melt scheme invoked, the faster the ice advects out from the pack, the faster the water column stratifies. The speed and the area of the bloom depend on the rate and extent of stratification. The model data compare favorably with field data.
  • Light adaptations of plants: a model based on seagrass Zostera Marina L.

    Dennison, William (1979-12)
    Adaptations to light by a temperate seagrass, Zostaro: marina L. (eelgrass), were investigated along a depth transect representing a gradient of plant development. Various light adaptive strategies are proposed in a conceptual model and tested along the natural gradient and under in situ light manipulation experiments. The major light capturing strategy which Zostera employs is that of changing leaf area. Chlorophyll a to b ratios and amounts, measures of adaptation to light quality and quantity, demonstrated little or no adaptive trends when integrative samples were used. The altered light experiments did not affect chlorophyll content but did affect leaf production rates. Although the relative vertical distribution of leaf area is constant along the transect, the absolute leaf area varies, as measured by leaf area index (LAI = area of leaves/area of bottom). A measured maximum LAI of 17 is higher than other aquatic and most terrestrial ecosystems.
  • Satellite evidence of physical features and processes in the Bering Sea

    Paluszkiewicz, Theresa (1982-05)
    Satellite infrared imagery is used to study temporal and spatial relationships of physical features and processes in the Bering Sea. A two-year collection of enhanced infrared imagery reveals that the maximum extent of the ice corresponds with the location of the Bering Slope current. Sea surface temperature patterns visually correlate with the 50-m and 70-m bathymetric contours. Processes which establish fronts in these regions are possible explanations for this correlation. Warm surface water extending from the Gulf of Alaska, through the Aleutian passes into the Bering Sea, is found simultaneously with warm surface water and eddies along the shelf break. Spatial and temporal relationships of these patterns imply surface circulation in the Bering Sea basin with inflow of Gulf of Alaska water through the Aleutian passes, cyclonic flow in the basin, and flow along the shelf by the Bering Slope current. Several generating mechanisms for the eddies are proposed.
  • Diving physiology of the ringed seal: adaptations, capability and implications

    Ferren, Howard Jennings (1980-08)
    Adaptations that influence duration of diving in the ringed seal, Phoaa (Pusa) hispida were examined. Mean blood volume was 234 ml/kg lean body mass (LBM) and oxygen capacity was 30.7 ml O2/100 ml of whole blood, yielding a total blood oxygen capacity of 70 ml O2/kg LBM. Abrupt and prolonged bradycardia occurred upon submersion. Experimental dives indicated submersion durations of up to 18 minutes before the onset of physiological dysfunction. The percentage of LBM represented by the brain is least in the relatively large Weddell seal (0.2%), greater in the harbor seal (0.7%) (the compared species) and greatest in the ringed seal (1.4%); this sets the requirement for minimum obligatory oxygen consumption. The differences observed in diving durations between the three species is considered to be mainly the consequence of brain/body size relationship.
  • Reproductive and larval biology of northern shrimp, Pandalus borealis Kroyer, in relation to temperature

    Nunes, Pepsi (1984-05)
    The northern shrimp, Pandalus borealis Kr^yer, is an important fishery resource in Alaska. However, a drastic decline in the commercial catch since 1978 poses a serious problem for the fishery. This study examined the effects of temperature on reproduction and larval survival of P. borealis. These are factors though to be vital to the determination of year class strength. P. borealis was found to have narrow thermal requirements for egg production with moderate (6°C) to low (3°C) temperatures generally more favorable than high (9°C) temperatures. In contrast with egg production, larval survival was enhanced by higher (6 and 9°C) temperatures. This study provides useful information for management of the fishery by demonstrating that temperature can trigger flucuations in the commercial catch from 5-50% through its effects on rates or reproduction and larval survival, and thereby population size. In warm water areas averaging >6°C, temperature exerts its main influence on reproduction, causing fecundity to vary by as much as 50%. While in colder areas average <3°C, fecundity and larval survival can vary with temperature by as much as 20 and 40%, respectively. Use of the information derived here requires monitoring temperature in the major fishery areas to detect changes in abundance of ovigerous females, egg number and larval mortality. Changes in these parameters are valuable indicators of stock condition when combined with abundance surveys and fishing intensity estimates.
  • The life history of the intertidal barnacle, Balanus balanoides (L.) in Port Valdez, Alaska

    Rucker, Tami Louise (1983-09)
    The life history of the boreo-arctic barnacle Batanus balanoides was examined at three study sites in Port Valdez. Ovarian tissue development began in early summer. Fertilized eggs, evident by September, were brooded throughout the winter. Larval release was synchronous with the spring phytoplankton bloom. Settlement was observed in April and continued until June. Maximal shell growth occurred immediately subsequent to assimilation of organic material from the spring bloom. Seasonal fluctuations in body weight were noted and reflect feeding, spermatogenesis, and energy transfer to other biological processes (i.e., shell growth and reproduction). Mortality, greater for juveniles than adults, resulted from seasonal stresses (lowered salinity and heightened sedimentation), spatial competition, predation, and pollutants (hydrocarbons). Once life-history events were confirmed for barnacles in Port Valdez, comparisons of trends observed at the three sites were possible. Differences between populations were evident and were attributed to the unique micro-habitats of the study sites.

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