Now showing items 21-40 of 198

    • 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.
    • The Geochemistry Of Manganese, Iron And Phosphorus In An Arctic Lake

      Cornwell, Jeffrey Clayton (1983)
      Sediment redox processes were investigated in an oligotrophic, arctic lake containing metal oxide crusts in oxidizing surficial sediments (up to 22% Mn and 26% Fe). Toolik Lake, Alaska, a 12,000 year old kettle lake, has the lowest Pb-210 derived sedimentation rates reported for any lake (27 g m('-2) yr('-1)). Three independent methods for estimation of Mn, Fe and P retention within the lake (stream budgets, sediment traps and sediment burial rates) provide similar rates. Of the amounts entering the lake, 28% of P, 50% of Mn and 55% of Fe are retained. Common water column removal mechanisms for these elements and organic C are suggested by sediment trap data. A steady state diagenetic model with terms for diffusion, reduction and oxidation shows that Mn and Fe crusts migrate within surficial sediments. Metal oxide burial rates are equivalent to oxide dissolution rates (reduction), rates of upward diffusion of soluble divalent metals and metal precipitation rates (oxidation). High inputs of labile Mn and Fe from streams, plus low sedimentation and organic matter oxidation rates are important for crust formation. Approximately 12% of Mn and 2% of acid reducible Fe retained by the lake since its formation exist as diagenetic oxides; the rest is buried within reducing sediment. Sediment inorganic P migrates with Fe to form P enriched sediment zones with pore water PO(,4) concentrations beneath these zones regulated by vivianite (Fe(,3)(PO(,4))(,2) 8H(,2)O) formation. The migration of Mn and Fe within sediments results in the enrichment of Ba, Co, Ca, Ni, Ra-226 and carbonate in metal oxide enriched sediments. Barium is enriched in Mn crusts because of diagenetic migration.
    • Variability In The Circulation, Temperature, And Salinity Fields Of The Eastern Bering Sea Shelf In Response To Atomospheric Forcing

      Danielson, Seth Lombard; Weingartner, Thomas; Aagaard, Knut; Coyle, Kenneth; Hedstrom, Katherine; Kowalik, Zygmunt (2012)
      Although the Bering Sea shelf plays a critical role in mediating the global climate and supports one of the world's largest fisheries, fundamental questions remain about the role of advection on its salt, fresh water, heat and nutrient budgets. I quantify seasonal and inter-annual variability in the temperature, salinity and circulation fields. Shipboard survey temperature and salinity data from summer's end reveal that advection affects the inter-annual variability of fresh water and heat content: heat content anomalies are set by along-shelf summer Ekman transport anomalies whereas fresh water content anomalies are determined by wind direction anomalies averaged over the previous fall, winter and early spring. The latter is consistent with an inverse relationship between coastal and mid-shelf salinity anomalies and late summer -- winter cross-shelf motion of satellite-tracked drifters. These advection anomalies result from the position and strength of the Aleutian Low pressure system. Mooring data applied to the vertically integrated equations of motion show that the momentum balance is primarily geostrophic within at least one external deformation radius of the coast. Local accelerations, wind stress and bottom friction account for < 20% (up to 40%) of the along- (cross-) isobath momentum balance, depending on location and season. Wind-forced surface Ekman divergence is primarily responsible for flow variations. The shelf changes abruptly from strong coastal convergence conditions to strong coastal divergence conditions for winds directed to the south and for winds directed to the west, respectively, and substantial portions of the shelf's currents reorganize between these two modes of wind forcing. Based on the above observations and supporting numerical model integrations, I propose a simple framework for considering the shelf-wide circulation response to variations in wind forcing. Under southeasterly winds, northward transport increases and onshore cross-isobath transport is relatively large. Under northwesterly winds, onshore transport decreases or reverses and nutrient-rich waters flow toward the central shelf from the north and northwest, replacing dilute coastal waters that are carried south and west. These results have implications for the advection of heat, salt, fresh water, nutrients, plankton, eggs and larvae across the entire shelf.
    • Effects Of Glacial Discharge On Kelp Bed Organisms In An Alaskan Subarctic Estuary

      Sparkland, Tania Marie; Iken, Katrin; Braddock, Joan; Gradinger, Rolf; Himelbloom, Brian; Konar, Brenda; Whitledge, Terry (2011)
      Global climate warming is having large-scale, pronounced effects on the physical environment of Arctic and subarctic nearshore marine ecosystems, such as the widespread melting of glaciers. The purpose of this study was to determine how changing environmental conditions due to glacial melting affect subarctic kelp bed community structure and organism fitness. This study compared kelp bed community structure under disparate environmental conditions on a glacially-influenced and an oceanic shore in the same subarctic Alaskan estuary. Laboratory tests assessed the effects of varying salinity and irradiance on growth and physiological competence (as maximum quantum yield ( Fv/Fm)) of the dominant kelp, Saccharina latissima. Reciprocal in situ shore transplant studies examined seasonal growth, Fv/Fm, morphology and storage product levels (mannitol) in S. latissima. This study showed that kelp communities were distinctly different in these two nearshore regions within the same subarctic estuary. In addition, the kelp S. latissima from these two environments, exhibited phenotypic plasticity in terms of growth to varying levels of salinity and light availability, while both populations maintained high physiological competence year-round. However, this phenotypic plasticity was constrained within different seasonal growth patterns in the populations from the two shores, which likely are genetically fixed. This is the first time that phenotypic plasticity within a genetically fixed seasonal growth cycle has been described for macroalgae and especially for two populations in such close proximity. However, the ability to elicit plastic responses and seasonal adaptations in S. latissima may be limited and concerns remain about the long-term persistence of this and other important foundation species and nearshore habitats with continued climate change.
    • The Influence Of Habitat Complexity, Prey Quality, And Predator Avoidance On Sea Otter Resource Selection In Alaska

      Stewart, Nathan Lord; Ruess, Roger (2011)
      The differential selection of habitat by animals is one of the fundamental relationships that enable species to coexist. Habitat selection may be among various discrete categories (e.g., mudflat, boulder field, or meadow) or among a continuous array of characteristics such as vegetation percent cover, benthic substrate size, substrate rugosity, distance to prey resources, or distance to suitable escape terrain from predation. Sea otters are particularly suitable for resource selection studies because they are capable of selecting a wide variety habitat types in response to prey availability, competition, and predation. In Alaska, sea otters associate with a range of habitats types including continuous bedrock reefs in the western Aleutians to heterogeneous fjord systems in Kackemak Bay, Lower Cook Inlet. Sea otters inhabiting the western Aleutians exhibit highly restricted habitat selection patterns characteristic of declining populations. In contrast, sea otters inhabiting Kachemak Bay exhibit selective use of a broad range of habitat types. Many factors contribute to the selective use of habitats by animals, including habitat suitability, prey quality, and predation risk. This thesis was designed to test factors contributing to sea otter resource selection in an area undergoing population increase versus an area experiencing high predation pressure. The contribution of prey size, abundance, biomass, potential energy density are considered in addition to physical habitat characteristics such as grain size, rugosity, depth, structural habitat complexity, and exposure to prevailing weather. Findings suggest that foraging sea otters differentially select habitat and prey resources based on prey accessibility and not on prey abundance or potential prey energy density. Findings further suggest that sea otter foraging site selection is based on habitat complexity in areas with increasing populations, but in areas with high predation pressure, proximity to suitable escape terrain appears to be more important than prey quality or benthic habitat complexity.
    • Endocrine And Immune Profiles Of Immature Pinnipeds

      Keogh, Mandy Jean; Atkinson, Shannon; Castellini, Michael; Hellman, Tuula; Ortiz, Rudy; Runstadler, Jonathan (2011)
      There is increasing interest in assessing the health of individuals and populations of pinnipeds found in the North Pacific, primarily due to population declines leading to conservation concerns. This study assessed the "health" of animals by quantifying hormones associated with fat mass (leptin), lipid and water metabolism (cortisol and aldosterone), and growth and metabolism (thyroxine and triiodothyronine) as well as circulating total and differential leukocyte counts and in vitro proliferation of peripheral blood mononuclear cells (PBMC). Body mass and condition are influenced by an individual's disease and nutritional state. Glucocorticoids are known to affect the immune system and may be stimulated by a multitude of factors. I hypothesized that age or body mass would influence leukocyte counts, PBMC proliferation, and hormone concentrations in Steller sea lion (Eumetopias jubatus) pups and that the response of cortisol to an acute stressor would impact immune parameters in juvenile harbor seals (Phoca vitulina ). Further, given the inherent requirements of disturbance and animal handling necessary for sampling pinnipeds, the impact of these activities on endocrine and immune profiles was assessed. Total white blood cell (WBC) counts, neutrophil counts and T cell proliferation decreased with increasing age in Steller sea lion pups. However, no relationship between body condition index and circulating concentration of hormones quantified was detected. Circulating concentrations of cortisol, thyroxine, and triiodothyronine were influenced by the rookery disturbance. However, the variation attributed to the disturbance was low and did not alter total or differential WBC counts or in vitro proliferation of PBMC. In harbor seals, cortisol and aldosterone concentrations increased following an acute stressor which resulted in a stress leukogram. Total WBC decreased driven primarily by the decrease in neutrophil counts with simultaneous increase in lymphocytes leading to an overall decrease in neutrophil to lymphocyte ratio. These findings highlight the endocrine system's influence on the immune system in immature pinnipeds.
    • Describing Forage Fish Availability In Coastal Waters Of The Kodiak Archipelago, Alaska

      Guo, Lei; Wynne, Kate; Foy, Robert; Coyle, Kenneth; Hillgruber, Nicola; Schaufler, Lawrence (2010)
      Assessing the availability of forage fishes is key to understanding fluctuations in populations of apex predators that prey upon them, including pinnipeds and seabirds in the Gulf of Alaska. In this study, multiple aspects of forage fish availability were measured in coastal waters of the Kodiak Archipelago, Alaska, in May (2004 & 2005), August (2004 & 2005), November (2006), and April (2007). Efforts were focused on four pelagic species that consistently dominated midwater trawl catches and have been described as important prey for upper trophic level predators around the Archipelago: walleye pollock (Theragra chalcogramma), Pacific herring (Clupea pallasii), capelin (Mallotus villosus), and eulachon (Thaleichthys pacificus). Fatty acid and stomach content analyses were combined to estimate the diet composition of these forage fishes as a means of identifying the immediate source of energy they transfer to upper trophic level taxa. Values of copepod-originated fatty acids indicated underestimation of dietary copepods by stomach content analysis, which suggests that fatty acid analysis should be used to supplement conventional methodologies in forage fish field studies. Lipid content and fatty acid composition were highly variable within species, suggesting that the use of average values at the species level should be avoided in fine-scale ecological investigations. Mesoscale horizontal distribution and energy density of forage fishes were measured in May and August (2005) to assess the prey fields available to local apex predators over critical periods of their life history. Dense post-spawning aggregations formed seasonal energetic "hotspots", exemplified by herring schools on the northwest side of the Archipelago in May and capelin schools on the northeast side in August. Results presented in this dissertation offer key information needed to identify energetic pathways of significance to upper trophic level consumers in the Kodiak Archipelago. Understanding local trophic interactions and their role in regional apex predator population fluctuations will improve efforts to develop trophodynamic models and ecosystem-based fishery management plans in the North Pacific Ocean.
    • Idealized Modeling Of Circulation Under Landfast Ice

      Kasper, Jeremy Lucas; Weingartner, Thomas; Gradinger, Rolf; Hedstrom, Katherine; Johnson, Mark; Kowalik, Zygmunt (2010)
      Idealized analytical and numerical models are used to elucidate the effects of a spatially variable landfast ice cover on under-ice circulation. Three separate forcing mechanisms are investigated; lateral inflow onto an ice-covered shelf (an elevated sea level at the western boundary), a spatially uniform upwelling wind blowing along the seaward landfast ice edge and a buoyant inflow under the ice cover that enters the domain through the southern coastal wall. The idealized models are configured to resemble the shallow Alaskan Beaufort Sea shelf. Models show that the inclusion of landfast ice means shelf response is substantially different from an ice-free shelf. In the case of a lateral inflow, landfast ice spreads the inflow offshore (in a manner similar to bottom friction) but the change in surface stress across the ice edge (from ice-covered to ice-free) limits the offshore spreading. In the case of an upwelling wind along the ice edge, the low sea level at the ice edge (due to ice edge upwelling) leads to a cross-shore sea level slope between the coast (high sea level) and the ice edge (low sea level), which drives a geostrophically balanced flow upwind. In the absence of along-shore changes in wind or ice the circulation does not vary along the shelf and currents near the coast are O(10 -3) m s-1. Along- and cross-shore variations in the ice-ocean friction coefficient introduce differences in the response time of the under-ice flow and can lead to along-shore sea level slopes, which drive along-shore flows near the coast (< 0.06 m s-1). In the case of a time dependent buoyant inflow, the landfast ice spreads the buoyant inflow much farther offshore (~ 9 times the local baroclinic Rossby radius, ~ 45 km) than in the ice-free case (< 30 km). When the ice width is finite, the change in surface across the ice edge acts to restrict offshore flow (in the anti-cyclonic bulge) and inhibits onshore flow farther downstream.
    • Seabird Habitat Use And Zooplankton Abundance And Biomass In Relation To Water Mass Properties In The Northern Gulf Of Alaska

      De Sousa, Leandra; Coyle, Kenneth; Weingartner, Thomas; Barry, Ronald; Springer, Alan; Jr., George Hunt (2011)
      Understanding of biological and physical mechanisms that control the Gulf of Alaska (GOA) ecosystem is of major importance to predicting the responses of bird and zooplankton communities to environmental changes in this region. I investigated seasonal (March-October) changes in seabird abundance in relation to changes in zooplankton biomass and water mass properties from 1998 to 2003. Oceanodroma furcata and Fratercula cirrhata were most abundant during the peak of the zooplankton production season (May-August). Overall abundance of seabirds did not follow seasonal changes in zooplankton biomass. Seabird abundance was low in the study area when compared to other regions in the GOA. Furthermore, low bird densities suggest that productivity in this study area is not high enough to sustain a significant seasonal increase in local seabird abundance. I further investigated the distribution and abundance of seabird foraging guilds across the neritic and oceanic domains in relation to water mass properties and zooplankton biomass during March and April. Overall zooplankton biomass increased from the inner shelf to the oceanic domain. Highest density of subsurface-foraging seabirds occurred in the middle shelf and surface-feeding seabirds were most abundant in the middle shelf and oceanic domain. Murre (Uria spp.) abundance was positively correlated with the biomass of Thysanoessa inermis, and Northern Fulmars (Fulmarus glacialis) were associated with cephalopod paralarvae and Eucalanus bungii. Elevated biomass of Thysanoessa inermis in March and April may be an important factor influencing habitat choice of wintering murres in this region. Lastly, I investigated the inter-annual variation in the abundance of sixteen zooplankton taxa in relation to water mass properties during May from 1998 to 2009. Significant variations in temperature, salinity and zooplankton abundance were identified. Thysanoessa inermis and Calanus marshallae had increased abundances in years when there was a strong phytoplankton spring bloom preceded by anomalously cold winters. However, abundances of Pseudocalanus spp., Neocalanus plumchrus/Neocalanus flemingeri, Euphausia pacifica and Oithona spp. were not strongly affected by relatively higher mean water temperatures. The abundance of zooplankton in the northern GOA was highly influenced by advective processes.
    • Resource Partitioning Among Sympatric Stellar Sea Lions And Northern Fur Seals On Lovushki Island, Russia

      Waite, Jason N.; Andrews, Russel; Castellini, Michael; Atkinson, Shannon; Rea, Lorrie; Trumble, Stephen (2010)
      The competitive exclusion principle maintains that one of two non-interbreeding species occupying the same ecological niche and geographical territory will be displaced if population growth is not the same between species. Steller sea lions (Eumetopias jubatus; SSL) and northern fur seals (Callorhinus ursinus; NFS) breed sympatrically on four rookeries in the Russian Far East, creating the potential for inter-specific competition for limited prey resources. Approximately 1,000 SSL and 14,000 NFS breed on Lovushki Island in the Kuril Island chain. An additional 13,000--14,000 juvenile NFS are present during the breeding season. The partitioning of forage resources among breeding SSL and both breeding and non-breeding NFS from 2003--2008 was examined through analysis of prey remains recovered from scats and spews, stable isotope (SI) analysis of vibrissae, fatty acid (FA) analysis of blubber, and analysis of foraging behavior through satellite-linked telemetry. Analysis of prey remains indicated a biologically significant overlap in the prey species and size selection of SSL and juvenile NFS and significant differences between the diets of SSL and breeding NFS. SSL fed primarily on Atka mackerel, while breeding NFS fed primarily on cephalopods and northern smoothtongue. SI analysis indicated significant differences in the trophic level and relative foraging location. SSL foraged at a higher trophic level, nearshore, and benthically, while NFS foraged at a lower trophic level, offshore, and pelagically. Analysis of FA signatures also suggested significant differences in the relative diets of breeding NFS and SSL. Foraging behavior analysis also indicated that SSL foraged nearshore and benthically and breeding NFS foraged offshore and pelagically. The combination of these four methodologies suggests breeding NFS and SSL partition their forage resources by prey type and prey size, as well as spatially. This partitioning of resources between breeding animals currently allows both species to coexist within the same geographical region and likely reflected the differences in foraging abilities and provisioning strategies of the adults, as well as the fasting abilities of their pups. However, continued growth of the non-breeding NFS population on Lovushki Island may lead to the competitive exclusion of SSL due to inter-specific competition for food resources.
    • Development And Application Of A Methodology To Estimate Regional Natural Conditions For Trace Metals In Marine Sediments Of Southcentral Alaska's Coastal Region

      Dasher, Douglas H.; Kelley, John J.; Duffy, Lawrence; Mueter, Franz; Naidu, A. S.; Perkins, Robert (2010)
      Increasing levels of resource development and population growth along Alaska's relatively pristine coastline require responsible environmental stewardship that is based on scientifically defensible monitoring and assessment. This thesis develops a methodology to assess the spatial distribution of coastal sediment trace metals and estimate their natural condition along Alaska's coastline. Marine sediments provide a better integrated long-term signal for naturally occurring and anthropogenic chemicals than repeated water measurements. The first of three manuscripts reports on marine sediment trace metal concentrations from a probabilistic sampling survey of Alaska's Southcentral coastal region. Results are described on a proportional basis, i.e., percent of estuary area, for the distribution of As, Cd, Cr, Cu, Pb, Hg, Ni, Ag, and Zn in the sediments. With the exception of naturally elevated Cr and Ni at a site bounded by a chromite ore body, sediment trace metal concentrations measured represent non-analmous levels. The second manuscript develops natural conditions for fluvial trace metal inputs from two major Southeast Alaska coastal watersheds: Cook Inlet and Copper River. The stream sediment trace metal natural conditions place levels in the adjacent coastal sediments into context. Two exploratory data analysis techniques, the Tukey Box plot and Median + 2 Median Absolute Deviation, combined with geochemical mapping are used to develop stream sediment trace metal natural conditions. The third manuscript builds on the first two to develop a methodology to estimate coastal sediment natural conditions. Population estimates for the cumulative area 90% UCB 95% sediment trace metal of interest obtained from the sampling survey methodology and screened reference sites is used to establishing an upper threshold value for regional natural conditions. While this work establishes natural condition marine sediment trace metal levels for this region, the significance of these levels from an ecotoxciological perspective remains to be established. Additional studies are needed along other sections of Alaska's coastline, coupled with biological assessments, if Alaska is to develop relevant sediment quality guidelines.
    • Heat And Freshwater Controlling Processes On The Northern Gulf Of Alaska Shelf

      Janout, Markus A.; Weingartner, Thomas; Coyle, Kenneth; Hedstroem, Ketherine; Johnson, Mark; Okkonen, Stephen (2009)
      We examined conditions and processes that control the distribution of heat and freshwater on the northern Gulf of Alaska (GOA) shelf. Cross-shelf heat gradients are weak throughout the year, while salinity gradients are substantial due to the impact of coastal freshwater runoff. Outer shelf water properties are influenced by large anticyclonic eddies, while the inner and middle shelves may be regulated by wind and freshwater runoff dynamics around the Alaska Coastal Current (ACC). On the outer shelf, anticyclonic eddies propagate from the eastern GOA southwestward along the continental slope, where they favor on-shelf (off-shelf) transport of saline and nutrient-rich (fresh and iron-rich) waters Certain along-shelf locations are identified where low-salinity coastal waters are found near the shelfbreak within reach of eddies and may be regions of enhanced cross-shelf freshwater transport. The eddies have lifetimes of ~5 years and increase in size and sea level anomaly west of the Seward Line, which implies more vigorous eddy cross-shelf exchange in the northwestern GOA. By comparison, on the inner shelf the heat and freshwater distribution is dominated by large coastal river runoff, which forces the ACC and controls the vertical distribution of temperatures through stratification. In May 2007, the coastal GOA revealed some of the lowest ocean temperatures since the early 1970s, initiated by strong atmospheric cooling and reduced coastal runoff in November 2006. Stepwise regression shows that 81% of the variability of deep temperatures is explained by salinity stratification and air-sea heat fluxes. Weak baroclinic flow in May 2007 likely aided the cooling through reduced along-shore heat transport. A more detailed examination of heat transport indicated that along-shore heat flux convergence in the ACC may re-supply 10-35% of the heat removed by air-sea fluxes throughout the coastal GOA cooling season, while the annual mean cross-shore heat flux convergence is insignificant. Spatial gradients show increasing heat fluxes from off- to on-shore and from east to west. The cross-shore gradients result from wind speed gradients due to ageostrophic near-shore wind jets near coastal mountains, while the along-shore gradients result from larger-scale pressure systems. While the ACC advects coastal freshwater around the GOA shelf its waters are subjected to disproportional heat loss west of the Seward Line.
    • Organochlorines In Steller Sea Lions (Eumetopias Jubatus)

      Myers, Matthew John; Atkinson, Shannon; Krahn, Margaret; Rea, Lorrie; Castellini, Michael; Mellish, Jo-Ann; Burdin, Alexander (2009)
      Existing populations of Steller sea lions (Eumetopias jubatus ) have declined precipitously over the last half-century. Investigations into the cause of this downward trend have focused on many different possible factors. Toxicity caused by the accumulation of organochlorines (OCs), such as polychlorinated biphenyls (PCBs) and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane or dichlorodiphenyltrichloroethane (DDT), has been demonstrated in marine mammals and was considered here as one possible factor that may have contributed to the decline of Steller sea lions or their failure to recover. The focus of this project was to investigate the relationship of contaminant loads to hormone levels, specifically thyroid hormones and cortisol in Steller sea lions. Two approaches were taken to this study. Firstly, baseline hormone concentrations were identified for the thyroid hormones, thyroxine (T 4) and triiodothyronine (T3), and cortisol. This involves comparison and extrapolation. Secondly, possible risk effects were examined by comparing levels of OCs in captive and free-ranging Steller sea lions to known effects in related species with known physiological thresholds. Serum concentrations of total T4 were highest in Steller sea lions followed by total T3 concentrations. Concentrations of free T4 and free T3 were three to four orders of magnitude lower. Concentrations for all four thyroid hormone measurements tended to a lower level as animals matured beyond the neonatal stage. When thyroid hormones from captive sea lions were evaluated across seasons, all thyroid hormones were highest in the July to September period. Cortisol concentrations were similar in male and female pups. Cortisol varied with age but when considered in regards to time of year when sampled, followed a seasonal pattern. Cortisol was elevated in fall months in captive sea lions (non-pups), which is similar to what is seen in other marine mammals and is likely associated with the annual molt. Male pups from Alaska had lower levels of SigmaPCBs and SigmaDDT when compared to male pups from Russia. Female pups from Alaska were significantly lower in SigmaPCBs than Russian female pups as were female pups for SigmaDDT levels between areas. Anywhere from 12 to 64% (depending on rookery) of Steller sea lion pups investigated for contaminants had concentrations of SigmaPCBs that are high enough to cause physiological problems. Concentrations in blood taken monthly for 2 years in three captive Steller sea lions were similar at any given sampling time and followed a seasonal pattern with levels significantly higher in the summer months of July to September and lower in the three month winter period January to March. Concentrations of OCs in blubber samples collected quarterly for the captive females followed an analogous pattern to blood samples but the captive male sea lion was considerably lower and declined over the study period. A significant relationship between blubber contaminants and lipids was noted in the three captive Steller sea lions. Even though OC contamination has not been hypothesized to be the primary factor that precipitated the population decline, there is a potential for these chemicals to have a negative effect on the health of free-ranging Steller sea lions. These data suggest that concentrations of OCs in Steller sea lions may be high enough to cause endocrine or reproductive dysfunction and could potentially impact fertility or fecundity. Therefore, OC contaminants can not be dismissed as a contributing source to either the decline or the failure to recover of the Steller sea lion population.
    • Adaptations Of The Bacterial Flywheel For Optimal Mineral Cycling In Oligotrophic Surface Waters

      Gustafson, Elizabeth S.; Button, Don K. (2008)
      Nutrient cycling in a subarctic oligotrophic lake was explored using current kinetic theory for organisms adapted to low nutrient environments with emphasis on bacterial contributions to system function. Techniques were refined which minimize sample disturbance and contamination for the purpose of accurately measuring bacterioplankton activity. Seasonal variations in DNA content, cell mass, species composition, specific affinity for amino acids and cell yield were observed. Quasi-steady state formulae describe bacteria as a flywheel in nutrient cycling; energy is conserved within a relatively constant biomass by varying bacterial activity with nutrient availability. The bacterial flywheel paradigm provides a bacteriocentric view of mineral cycling, linking kinetics to specific cytoarchitectural properties while maintaining links to substrate and grazing pressures. As an extention of the microbial loop paradigm, the flywheel becomes essential at high latitudes. In winter, low solar input interrupts the microbial loop so that the dissolved organic carbon (DOC) pool is cycled through bacteria only. This activity allows bacterioplankton to persist through winter and respond rapidly to springtime warming and nutrients. Microbial adaptations to seasonal variations in nutrient availability and temperatures were examined within the bacterial flywheel framework. Organisms are well-adapted to a narrow (17&deg;C) in situ temperature range. Activation energies for small warming were low at the temperature extremes (20.6 kJ mol -1 at 0.5°C; -32 kJ mol-1 at 17°C) and high in spring (110 kJ mol-1 at 1.2°C). Nutrition varies by season, supplied in large part by amino acids in spring and summer. Winter growth rates are at least 0.013 day-1 whereas partial growth rate on amino acids for that season is only 2.8 x 10-5 day -1. It is proposed that winter organisms rely on diffusion transport and/or shift toward concurrent use of a large suite of substrate types for growth and maintenance.
    • Foraging Ecology And Nutritional Stress Of Tufted Puffins (Fratercula Cirrhata) Inferred From Stable Isotopes, Fatty Acid Signatures, And Field Endocrinology

      Williams, Cory T.; Buck, C. Loren (2008)
      Prey availability has a major impact on the reproductive output of seabirds, yet information on seabird diets throughout the breeding season is often lacking. Although reduced prey availability is known to affect the growth and survival of nestling seabirds, few studies have demonstrated similar effects on indices of adult body condition. I used stable isotopes and fatty acid (FA) signatures to investigate seasonal and age-related variation in the foraging niches of tufted puffins (Fratercula cirrhata). I conducted captive feeding experiments to determine whether inferences based on these techniques are affected by moderate food restriction during growth. I also examined how adult puffins prioritize the competing goals of maximizing the growth rate of their offspring and maintaining their own condition, as measured by body mass and by the stress hormone, corticosterone (CORT). Food restriction during nestling growth affected adipose tissue FA signatures and resulted in blood that was depleted in 15N and 13C relative to well-fed controls. However, effects of nutritional restriction on delta 15N, delta13C, and FA signatures were small compared to variability in prey, indicating physiological effects do not preclude use of these techniques as dietary tracers. Stable isotopes and FA signatures of free-living adults indicated foraging niches changed over the course of the breeding season. Stable isotopes suggest chick-rearing adults and nestlings feed at the same trophic level while FA signatures indicate that parents feed nestlings a diet different from their own. Body mass of adult puffins declined between incubation and chick rearing periods. For females the magnitude of mass decline did not differ between years, whereas for males the decline was greater in the year where young puffins fledged at a lower mass. In a separate analysis, baseline CORT values of adults of both sexes did not differ between years, but were lower than those observed in a separate study area during two consecutive years with low rates of nestling growth and survival. Assuming elevated CORT and reduced body mass impact survival and/or future fecundity, these results suggest the cost of reproduction may be higher for those adults able to fledge young in years characterized by low productivity.
    • Reproductive Potential Of Pacific Cod (Gadus Macrocephalus) In Alaska

      Ormseth, Olav Aleksander; Norcross, Brenda L. (2007)
      The reproductive potential of female fishes, which results from the number of eggs they produce and the quality of individual eggs, is a critical factor in fisheries biology. Reproductive potential is important to individuals because maternal fitness is the product of the number of offspring produced and how many offspring survive. The growth rate of populations and their capacity for supporting commercial fisheries also depend on the number of viable offspring that females produce. I studied the reproductive potential of female Pacific cod (Gadus macrocephalus) in the North Pacific Ocean. Pacific cod is an important ecological and economic resource, yet much of its reproductive biology remains unexplored. I used several different approaches to investigate whether egg number or egg size are more important in determining reproductive potential, and to evaluate factors that influence reproduction. An analysis of life history variation among Pacific cod in Canada and Alaska demonstrated that despite differences in life history strategies, females from different populations had similar lifetime reproductive success (a proxy for individual fitness). I also collected Pacific cod in the Gulf of Alaska, eastern Bering Sea, and western Aleutian Islands from 2002 to 2005. Biochemical analyses of Pacific cod eggs revealed that Pacific cod produce low-energy eggs that are adapted for rapid development on the seafloor. Larger females produce eggs with less arachidonic acid (a fatty acid that has been linked to egg quality) than smaller females, suggesting that they may sacrifice egg quality to maintain fecundity. Determination of fecundity and egg size in 590 females from different areas and years revealed that maternal length and weight are excellent predictors of fecundity, but that variability in egg size is not related to the age or size of females, The greatest difference in reproductive potential among years and areas was reduced egg size in the eastern Bering Sea in 2003, which may have been due to changes in ocean temperature or prey availability that impacted the ability of females to store energy. These results suggest that female Pacific cod maximize their fitness through increased egg production, not egg quality, and that their reproductive success is under strong environmental control.
    • Six Thousand Years Of Change In The Northeast Pacific: An Interdisciplinary View Of Maritime Ecosystems

      Misarti, Nicole; Finney, Bruce (2007)
      The goal of this thesis is to develop long-term records of North Pacific ecosystems and explore relationships between change in marine ecosystems and prehistoric Aleut culture through soil chemistry, isotope analyses of lake cores, and isotope analyses of bone from archaeological middens. Chemical analysis of soils yielded differences in soils of various archaeological features as well as middens of varying composition. Sites that had no middens were chemically distinguishable from sites that did have middens helping to define resource consumption in the local region. An important result of this study is that no single ecosystem (nearshore benthic, coastal pelagic or deep-ocean pelagic) experienced the same changes in delta13C and delta 15N over the past 4,500 years. This suggests that changes in climate affected different ecosystems in unique ways. Only one change spans all species studied, the decrease in modern delta13C in comparison to delta13C of prehistoric specimens. According to these comparisons, the modern Gulf of Alaska may not be in the highly productive state that it was for the past 4,500 years, with the possible exception of the Medieval Warm Period. Lake core sediment analysis suggests an increase in salmon stocks in the Gulf of Alaska beginning &sim;6,000 years ago, with a decrease during the Medieval Warm Period. In fact, salmon stocks in the Gulf of Alaska appear to be healthiest during periods of atmospheric cooler and wetter climate over the past 4,500 years. In comparing my paleoecological records to the archaeological record of the area it appears that humans were affected by changes in their environment but, even in relatively small numbers, humans also influenced local ecosystems for the past 6,000 years. By building on our understanding of long-term climate change and long-term fluctuations in ecosystems and trophic dynamics of species in the North Pacific, and through considering humans in the ecological context, we can better understand present conditions in marine ecosystems.
    • Physical And Biological Factors Affecting The Diel Vertical Migration Of Walleye Pollock

      Adams, Charles F.; Kelley, John J.; Coyle, Kenneth O. (2007)
      The mechanisms underlying diel vertical migration (DVM) in marine fishes are unclear, although it is generally thought that this behavior is influenced by light, hydrography, food availability and predator avoidance. In the North Pacific Ocean, walleye pollock (Theragra chalcogramma) undergo DVM as juveniles, ascending to the surface at night and returning to the bottom at dawn. Adults are generally considered demersal. The objective of this research was to examine the effect of light, temperature and prey availability on the DVM of adult pollock. The work was undertaken to further our understanding of pollock biology, and the mechanisms underlying DVM in marine fishes in general. The study was conducted in the northern Gulf of Alaska in April, August and November 2003. Trawls < 80 m in April, and < 50 m in August, suggested that at least some portion of the pollock population was ascending to within 20 m of the surface in spring and summer. In November, acoustic data and targeted hauls > 100 m indicated that adults were not ascending to the surface at night, and that DVM behavior was occurring at depth. Euphausiids were the primary component of the diet in April and August. Decapods, primarily the shrimp Pandalus borealis, were the main component of the diet in November. Pollock passed through the thermocline during their ascent to the surface at night in August, and there was no relationship between the mean depth of pollock and the isolume (line of equal light intensity) necessary for visual foraging. In contrast, there was a significant relationship between the biomass of adult pollock above the 200 m isobath and the isolume necessary for visual foraging in November. Pollock did not pass through the thermocline at this time. It was concluded that in August adults ignore the isolume and thermocline, simply tracking the movements of euphausiid prey to feed upon them near the surface at night. In November, when euphausiids are no longer in patches, pollock shoals migrate up and down with the isolume necessary for visual foraging to feed on decapods.
    • Population Structure And Behavior Of Pacific Halibut

      Seitz, Andrew C.; Norcross, Brenda (2006)
      Pacific halibut (Hippoglossus stenolepis) is not managed on regional scales with separate population dynamics, but rather as a single, fully mixed population extending from California through the Bering Sea. However, some of the evidence from which this paradigm was established is questionable and I hypothesize that there are separate spawning populations of Pacific halibut in three regions, the Gulf of Alaska, Bering Sea and Aleutian Islands, because these regions are geographically separated by land masses and/or deep water passes that may prevent movement by adults. Pop-up Archival Transmitting (PAT) tags were attached to Pacific halibut in each region to examine their movement and behavior. First, geolocation by ambient light was able to discern basin-scale movements of demersal fishes in high latitudes and therefore this technique provided a feasible method for providing scientific inference on large-scale population structure in Pacific halibut. Second, because seasonally low ambient light levels and inhabitation of deep water (>200 m) restricted geolocation by light during winter, an alternative method, a minimum distance dispersal model, was developed for identifying migration pathways of demersal fish in the Gulf of Alaska based on daily maximum depth. Third, the PAT tags provided no evidence that Pacific halibut in the southeastern Bering Sea and Aleutian Islands moved among regions during the mid-winter spawning season, supporting my hypothesis of separate populations. Fourth, geographic landforms and discontinuities in the continental shelf appeared to limit the interchange of Pacific halibut among areas and possibly delineate the boundaries of potential populations in the Gulf of Alaska and eastern Bering Sea, with apparent smaller, localized populations along the Aleutian Islands. This possible population structure may be reinforced by regional behavioral variation in response to the environment. Future research should be directed at quantifying the exchange of individual fish among regions for possible local area management plans that more accurately reflect population structure.
    • Distribution, Growth And Egg Production Of Euphausiids In The Northern Gulf Of Alaska

      Pinchuk, Alexei I.; Hopcroft, Russell (2006)
      The euphausiids Thysanoessa inermis, Thysanoessa spinifera and Euphausia pacifica are key pelagic grazers and important prey for many vertebrates in the Gulf of Alaska (GOA). This thesis provides the first account of distribution, egg production, growth, development, and temporal variability in abundance of the euphausiids in relation to environmental variations in the northern GOA. T. inermis and T spinifera were abundant on the shelf within 120-130 km from the coast, while E. pacifica originated from offshore and was advected onto the shelf during summer. E. pacifica produced multiple broods with brood size strongly related to ambient chlorophyll a concentrations. In contrast, T. inermis released eggs once in the season and its brood size did not depend on chlorophyll content. Early development of these species showed a remarkably similar response to changes in temperature. The highest molting increments were observed during the spring phytoplankton bloom for T. inermis, and in summer for T. spinifera and E. pacifica, suggesting coupling with food availability. The molting rates were strongly influenced by temperature. Growth rates depended on euphausiid size, and were close to 0 in early spring, reaching maximum values in May (0.123 mm d-1 or 0.023 d -1 for T. inermis) and July (0.091 mm d-1 or 0.031 d-1 for T. spinifera). The growth rates for E. pacifica remained below 0.07 mm d -1 (0.016 d-1) throughout the season. The relationship between T. inermis weight specific growth rate (adjusted to 5�C) and ambient chlorophyll-a concentration fit a Michaelis-Menten curve (r2=0.48), but such relationships were not significant for T. spinifera or E. pacifica. Reproduction of T. inermis occurred during April in 1998 and 2003, and was extended through May in 1999-2002. The spawning of T. inermis and T. spinifera was related to the spring diatom bloom on the inner shelf, while the spawning of E. pacifica occurred later in season, when the water temperature increased. A strong increase in abundance of T. inermis, associated with the extended colder phase in the North Pacific, indicates that progressive cooling in 1999-2002 may have resulted in greater reproductive success of early spawning T. inermis on the inner shelf.