• 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.
    • Idealized Modeling Of Seasonal Variation In The Alaska Coastal Current

      Williams, William James; Weingartner, Thomas (2003)
      Analytical and idealized-numerical models were used to understand the physical processes that govern the seasonal variation and fate of the freshwater in the Alaska Coastal Current (ACC). The ACC is forced by freshwater inflow and by mean easterly winds that cause downwelling over the shelf. Two-dimensional modeling using a line-source buoyant inflow gives the coastal current depth <math> <f> H=<fr><nu>3<sup>2/3</sup></nu><de>2</de></fr><fen lp="par"><fr><nu> f<sup>2</sup>Q<sup>2</sup></nu><de>g<sup>'</sup></de></fr> <rp post="par"></fen>t<sup>2/3</sup></f> </math> and coastal current width <math> <f> Y<inf>2D</inf>=3<sup>1/3</sup><fen lp="par"><fr><nu>g<sup>' </sup>Q</nu><de>f<sup>2</sup></de></fr><rp post="par"></fen><sup> 1/3</sup>t<sup>1/3</sup></f> </math>, where f is the Coriolis frequency, g ' is reduced gravity, Q is inflow rate and t is time since inflow began. Addition of downwelling wind-stress causes a steep coastal current front that intersects the bottom and is either convecting, stable and steady, or stable and oscillatory depending on <math> <f> <fr><nu>D</nu><de><g>d</g><inf>*</inf></de></fr></f> </math> and <math> <f> <fr><nu>b<inf>y</inf></nu><de>f<sup>2</sup></de></fr></f> </math>, where D is bottom depth, delta* is an Ekman depth and by is the cross-shelf buoyancy gradient. Three-dimensional modeling of a half-line source initially develops two-dimensionally but becomes three-dimensional from a balance between coastal influx of buoyancy and its downstream transport. This balance results in a coastal current depth limit <math> <f> H<inf><rf>max</rf></inf>=<fen lp="par"><fr><nu>2Qf</nu><de>g<sup> '</sup></de></fr><rp post="par"></fen><sup>1/2</sup>x<sup> 1/2</sup></f> </math>, where x is along-shelf distance. This limit is unchanged under downwelling wind-stress and is reached on time scales of less than 1 month for the ACC. The half-line source coastal current width develops as <math> <f> Y<inf>2D</inf></f> </math> away from the beginning of the line source. Imposition of a downwelling wind-stress tau results in an approximate balance among wind-stress and along- and cross-shelf momentum advection so that the current width is reduced to <math> <f> Y<inf>wind</inf>&ap;L<inf>D</inf><fen lp="par"><fr><nu>Qf</nu> <de><g>t</g>/<g>r</g><inf>0</inf></de></fr><rp post="par"></fen><sup> 1/2</sup></f> </math>, where LD is the Rossby radius of deformation. Waves and eddying motions eventually grow in the half-line source coastal current with wavelengths proportional to the coastal current width and with a downstream phase speed slower than the maximum current speed. These features cause an offshore flux of buoyant water, a broader coastal current and accumulation of buoyancy on the shelf. Increasing downwelling wind stress reduces the effects of the instabilities. Although buoyancy accumulates on the shelf during most model runs, there is little accumulation under maximum winter downwelling wind-stress. This suggests that freshwater accumulates on the shelf from spring through fall, but is then transported downstream during winter.
    • Influence of physical and biological oceanography on the structure of the seabird community in the northeastern Chukchi Sea

      Gall, Adrian E.; Blanchard, Amy L.; Weingartner, Thomas J.; Mathis, Jeremy T.; Hopcroft, Russell R.; Day, Robert H. (2015-12)
      The Chukchi Sea is losing seasonal ice cover as global temperatures rise, facilitating human access to the region for activities such as oil and gas exploration, shipping, and tourism. Processes and responses to environmental change by marine ecosystems are often challenging to quantify because they are hidden under water. Seabirds, however, offer visible evidence of the health and status of marine ecosystems. I studied the community structure, variability in abundance and distribution, and habitat associations of seabirds in the eastern Chukchi Sea. My results provide insights into the influence of climate change on seabirds and a benchmark against which to evaluate possible impacts of anthropogenic activity. Repeated sampling of systematic transects in the northeastern Chukchi Sea during the ice-free seasons of 2008-2012 showed that the community consisted of ~40 species and was dominated numerically by planktivorous seabirds, particularly Crested Auklets (Aethia cristatella) and Short-tailed Shearwaters (Puffinus tenuirostris). In contrast, benthic-feeding birds were rare. The abundance of seabirds in the offshore northeastern Chukchi Sea varied by up to two orders of magnitude among years and birds generally were more abundant in September than August. Despite these seasonal and interannual variations in abundance, the species composition was similar among years, with anomalies occurring only in years of persistent ice cover. I compared data from this recent period (2008-2012) with data from historical surveys (1975-1981) to evaluate decadal trends in seabird abundance and composition and related those changes to reductions in seasonal ice cover. The seabird community shifted from one consisting primarily of piscivorous seabirds to one consisting primarily of planktivorous seabirds. This shift suggests that zooplankton prey are more accessible now to avian predators as seasonal ice cover has declined. I explored the relationships between seabirds, hydrography, and zooplankton abundance with spatially explicit generalized additive models. The associations of seabirds with habitat characteristics varied with foraging method and preferred prey. Species that fed primarily by pursuit diving were more abundant in warm, weakly stratified water, whereas surface-feeding species were more abundant in cold, strongly stratified water. Planktivorous seabirds (auklets, shearwaters, and phalaropes) were more abundant within 20 km of thermal surface fronts and in contrast, omnivores (gulls and murres) were more abundant far from thermal fronts. For 5 of the 8 seabird species, information about prey biomass improved predictions of seabird abundance, although the relationships were not as clear as they were for the physical habitat characteristics indicative of processes that aggregate prey. Advective processes that transport oceanic species of zooplankton from the Bering Sea to the Chukchi Sea, together with the local influence of sea ice on physical and biological processes, strongly influence the distribution of seabirds, particularly the planktivorous species. Scientists and decision-makers can use the results of this multi-species and multi-disciplinary study as a benchmark to assess the ecological consequences of anthropogenic activity against the backdrop of climate change that is affecting the Chukchi Sea.
    • The influence of rookery terrain on population structure, territorial behavior, and breeding success of Steller sea lions in the Gulf of Alaska

      Smith, Louise N. (1988-05)
      The effect of rookery terrain on population structure, territorial behavior and breeding success of Steller sea lions was assessed at two rookeries, in the northern Gulf of Alaska. The sea lions using Sugar loaf and Marmot Islands differed in age structure, juveniles being absent from Sugar loaf but present on Marmot during the breeding season. Territory boundaries of breeding bulls on Sugarloaf were stable, and were unaffected by tides. Territory boundaries on Marmot were unstable, shifting with the tide. Territorial bulls occupied two types of territories on Sugarloaf Island (landlocked and water-access) and three types on Marmot (landlocked, tidal and semiaquatic). The behavior of territorial bulls on Marmot was influenced by tides and presence of juvenile animals. These factors were not important on Sugarloaf. The breeding success of territorial bulls was unaffected by location of territory on Sugarloaf. Territory location was important in the breeding success of Marmot Island bulls.
    • The Influence of terrestrial matter in marine food webs of the Beaufort Sea shelf and slope

      Bell, Lauren; Iken, Katrin; Okkonen, Steve; Wooller, Matthew; Bluhm, Bodil (2015-05)
      Terrestrial organic matter (OMterr) can function as a food source for Arctic marine consumers, though the relative contribution of OMterr to the structure and efficiency of marine food webs compared to marine production is unclear. Forecasted increases in OMterr inputs to the Arctic Beaufort Sea necessitate a better understanding of the proportional contribution of this organic matter source to the trophic structure of marine communities. This study investigated the relative ecological importance of OMterr across the Beaufort Sea shelf and slope by examining differences in community trophic structure concurrent with variation in terrestrial versus marine organic matter influence. Hydrogen stable isotope ratios (δD) of surface water, surface sediment particulate organic matter (sPOM), and selected benthic consumers were used as an exploratory assessment of freshwater and OMterr distribution in the Beaufort Sea. δD values of surface water confirmed the widespread influence of Canada's Mackenzie River plume across the Beaufort Sea; however, δD values of terrestrial and marine production were not sufficiently distinguishable to differentiate organic matter sources in consumers. Carbon stable isotope ratios (δ¹³C values) of pelagic particulate organic matter (pPOM) and marine consumers confirmed a significant decrease in OMterr presence and utilization by consumers with increasing distance from the Mackenzie River outflow. Food web length, based on the nitrogen stable isotope ratios (δ¹⁵N values) of marine consumers, was longer closer to the Mackenzie River outflow both in shelf and slope locations due to relatively higher δ¹⁵N values of pelagic and benthic primary consumers. The absence of macrofaunal consumers at the lowest trophic levels of OMterr-influenced food webs was interpreted to result from the prior metabolic turnover of OMterr by the microbial loop, which was not sampled in this study. The inferred presence of strong microbial processing of OMterr in the eastern regions of the Beaufort Sea resulted in a higher proportion of relative epifaunal biomass occupying higher trophic levels, suggesting that OMterr as a basal food source can provide substantial energetic support for higher marine trophic levels. These findings challenge the current conception of low terrestrial matter contributions to the Arctic marine food web, and compel a more specific understanding of energy transfer through the OMterr-associated microbial loop.
    • Insight into the diet history of ice seals using isotopic signatures of muscle tissue and claws

      Carroll, Sara Shanae; Norcross, Brenda; Horstmann-Dehn, Larissa; Quakenbush, Lori; Wooller, Matthew (2012-05)
      Climate change and sea ice reduction in the Arctic may impact foraging of ice-associated predators. The goal of my thesis work was to examine interannual differences in the diet of ringed, bearded, spotted, and ribbon seals as described by stable nitrogen and carbon isotope ratios of muscle tissue and claws to assess foraging plasticity. Isotopic mixing models from muscle data were used to describe the proportional contribution of prey groups during 2003, 2008-2010. Results showed a higher proportional contribution of smelt (Osmeridae) and benthic prey to ringed and bearded seal diets in 2003 compared to 2008-2010. Seasonal keratin layers deposited in claws can document trophic history up to about 10 years. During 2007 (record ice minimum), proportionally more ringed seals fed at a lower trophic level, while spotted seal adults and young-of-the-year fed at a lower trophic level during 2006. Bearded seals may have been foraging more pelagically from 2008 to 2010. Ice seals may be taking advantage of more abundant pelagic crustaceans as the Arctic ecosystem changes to a pelagic-dominated food web. Interannual variations and high variability among species and individual diets illustrate the opportunistic nature and flexibility of ice seals to changes in prey composition.
    • Interannual variability of epibenthic communities in the Chukchi Sea, Alaska

      Powell, Kimberly Keeler; Konar, Brenda; Coyle, Ken; Winsor, Peter (2015-08)
      Epibenthic communities contain a wide range of organisms and serve an important role in marine ecosystems. They are involved in carbon remineralization, benthic production, and are important prey items for higher trophic levels. Arctic epibenthic communities may be experiencing significant changes in species composition, abundance, and biomass at both short and long term time scales. While epibenthic communities may be responding to long term shifts in the environment, differentiating long term trends from short term interannual variation can be problematic. The present study examined interannual differences of epibenthic communities and potential environmental drivers of their variability in the Chukchi Sea. For this, a plumb-staff beam trawl was used to sample epibenthic species composition, abundance, and biomass of the dominant invertebrate taxa at 71 stations around the Chukchi Sea during the ice free seasons of 2009, 2010, 2012, and 2013. Over the entire study area and within a smaller area with the most temporal coverage, the largest separation was between 2009 and 2013, with more difference between 2009 to 2010 than between 2012 and 2013. Crustaceans were the most significant contributors to community composition, based on abundance, and biomass. The important environmental drivers that varied along with the epibenthic community in some but not all years included bottom water temperature, salinity, dissolved oxygen, mean sediment chlorophyll a, and sediment organic matter. In contrast, sediment grain size was important in all years and, therefore, was the least likely to contribute to the biological variability among years. While these data provide a benchmark on interannual variability of epibenthic communities in the Chukchi Sea, more monitoring is essential to determine long term trends.
    • Interannual variations in the carbon to chlorophyll a ratios during the spring bloom in Prince William Sound, Alaska

      Tamburello, Kathereen Rachel (2005-05)
      The carbon to chlorophyll a ratio of phytoplankton during the spring bloom in Prince William Sound, Alaska was investigated for 3 seasons and related to major physical and chemical variables. Carbon to chlorophyll a ratios (C:Chl) were determined by two methods, based on particulate organic carbon to chlorophyll (POC:Chl) and phytoplankton cell carbon to chlorophyll (PCC:Chl). These ratios were compared to a more commonly used estimate, a fixed ratio of C:Chl, taken from literature, for the spring phytoplankton community. The hypothesis that the C:Chl ratios were significantly different between years was proven false. This research indicates that the C:Chl ratio is primarily determined by species composition of the phytoplankton community rather than external factors such as nutrients, temperature or salinity. In addition, this research indicates that the identification and enumeration method, although rarely used because it is the most time and labor intensive method, provides the best estimate of phytoplankton carbon. The mean PCC:Chl ratio for all three years was 18, and is the best fixed ratio to estimate spring phytoplankton carbon in Prince William Sound when an EI Niño is not present.
    • Interrelationship among temperature, metabolism, swimming performance and recovery in Pacific cod (Gadus macrocephalus): implications of a changing climate

      Hanna, Shannon K. (2006-12)
      Physiological constraints are suggested to contribute to the observed changes in relative abundance of Pacific cod (Gadus macrocephalus) seen in association with interdecadal changes in sea surface temperatures. To examine this concept, two experiments were conducted to determine critical swimming speed (Ucrit), rates of oxygen consumption and recovery post-exhaustion of adult cod acclimated to different temperatures. In addition, hematocrit and plasma concentrations of cortisol, metabolites and ions from resting and exhausted fish were measured to assess the impact of swim trials on fish condition. In experiment one, fish acclimated to 4°C had similar mean Ucrit (1.07 BL/s) and resting metabolic rates (35.34 mg O₂/kg⁰⁸/hr) compared to fish acclimated to 11°C fish (1.07 BL/s; 49.43 mg O₂/kg⁰⁸/hr). Similarly, concentrations of blood constituents differed little between temperature treatments; each exhibited increases in plasma cortisol and metabolites from pre- to post-swim. Experiment two illustrated few differences in rates of recovery between temperature groups (2 and 7°C). After four hours of recovery there was no evidence of plasma cortisol or metabolites returning to pre-swim concentrations in either temperature group. It seems unlikely that physiological constraints on the metabolic performance of adult Pacific cod contribute to changes in their relative abundance.
    • Intertidal community development along a distance/age gradient in a tidewater glacial fjord

      Sharman, Lewis Crook (1987-12)
      Glacier Bay has recently undergone rapid deglaciation, exposing new substrates to colonization and biological development. There is a clearly defined increase in marine intertidal community development with substrate age (0-200 y) and distance (0-90 km) from present-day locations of tidewater glacier termini. The objectives of this research were (1) to describe length-of-fjord patterns of intertidal community composition and corresponding gradients of the near-surface marine physical environment and (2) to use this approach to evaluate the relative contributions of substrate age and physical factors to determining the degree of community development. Distance and age were almost perfectly correlated. Intertidal species richness increased linearly with distance/age. Environmental factors can be grouped into those that also varied linearly along this gradient, and those that varied exponentially. Distance from the glaciers and the other linearly correlated marine environmental factors of water temperature, salinity, and suspended particulate nitrogen factors are probably the most important determinants of intertidal community development.
    • Investigating marine particle distributions and processes using in situ optical imaging in the Gulf of Alaska

      Turner, Jessica S.; McDonnell, Andrew; Johnson, Mark; Islas, Ana Aguilar (2015-12)
      The Gulf of Alaska is a seasonally productive ecosystem surrounded by glaciated coastal mountains with high precipitation. With a combination of high biological production, inputs of suspended sediments from glacial runoff, and contrasting nutrient regimes in offshore and shelf environments, there is a great need to study particle cycling in this region. I measured the concentrations and size distributions of large marine particles (0.06-27 mm) during four cruises in 2014 and 2015 using the Underwater Vision Profiler (UVP). The UVP produces high resolution depth profiles of particle concentrations and size distributions throughout the water column, while generating individual images of objects >500 μm including marine snow particles and mesozooplankton. The objectives of this study were to 1) describe spatial variability in particle concentrations and size distributions, and 2) use that variability to identify driving processes. I hypothesized that UVP particle concentrations and size distributions would follow patterns in chlorophyll a concentrations. Results did not support this hypothesis. Instead, a major contrast between shelf and offshore particle concentrations and sizes was observed. Total concentrations of particles increased with proximity to glacial and fluvial inputs. Over the shelf, particle concentrations on the order of 1000-10,000/L were 1-2 orders of magnitude greater than offshore concentrations on the order of 100/L. Driving processes over the shelf included terrigenous inputs from land, resuspension of bottom sediments, and advective transport of those inputs along and across the shelf. Offshore, biological processes were drivers of spatial variability in particle concentration and size. High quantities of terrigenous sediments could have implications for enhanced particle flux due to ballasting effects and for offshore transport of particulate phase iron to the central iron-limited gyre. The dominance of resuspended material in shelf processes will inform the location of future studies of the biological pump in the coastal Gulf of Alaska. This work highlights the importance of continental margins in global biogeochemical processes.
    • Investigations of the role of lipids in marine mammal diets, health and ecology

      Mau, Tamara Lynn (2004-05)
      Lipids are essential to many aspects of marine mammal biology. I investigated the amount, type and flux of lipids under a variety of natural and controlled nutritional and dietary conditions, in order to increase our knowledge of marine mammal diets, health and ecology. First, I examined the influence of biological and environmental variables on the quantity and quality of blubber, and their importance in establishing condition indices in the bowhead whale. Blubber was heterogeneous in composition, varying by both site and depth. Sex, age-class, season and body length were all significant factors in determining lipid content (quality) of blubber. Blubber thickness (quantity) was highly correlated with body length after?9 m. Blubber lipid content at umbilicus sites and inner depths was most variable and presumably most responsive to nutritional changes. Blubber properties appeared to exceed what was necessary for insulation, further supporting the concept for the need to store energy as a consequence of the large seasonal and annual variability of food availability in the arctic environment. These data establish a baseline for long-term monitoring of bowhead whale health and population condition. Second, I addressed post-mortem changes in blubber composition of a stranded humpback whale. Lipid content decreased due to tissue decomposition by as much as 24%, limiting the ability to accurately assess nutritional status and health. Finally, in response to a growing need for validation of the use of fatty acid profiles as dietary tracers in top marine predators, I investigated the effects of prey switching on fatty acid profiles in plasma and red blood cell membranes (RBCs) of captive harbor seals. In plasma, nine of fifteen fatty acids responded significantly with prey switching, compared to only three plus one ratio in RBCs. Season and total daily lipid intake also affected the level of some plasma fatty acids. Diet was reliably predicted from fatty acid profiles in plasma after two weeks and in RBCs at four months using discriminant function analysis. Plasma and RBC fatty acid profiles provided an integration of dietary history, representing short-term and long-term 'dietary windows, ' respectively.
    • Kelp bed variability and fish population dynamics in Kachemak Bay, Alaska

      Hamilton, Judith Ann (2004-08)
      Understanding interactions between kelp beds and fishes is essential because anthropogenic changes and natural variability in these beds (composition, density, and distribution) may affect available habitat for fishes. In Alaska, little is known about the annual and seasonal variability of macroalgal cover in kelp beds and corresponding changes in associated fish populations. This study investigated natural variability using monthly SCUBA surveys in Kachemak Bay, Alaska from May 2002 to September 2003. Ten shallow (approximately 7m water depth) nearshore kelp beds with varying degrees of macroalgal cover were surveyed visually for fishes and kelp, and measurements of environmental variables were collected. These kelp beds had a persistent, perennial-dominated understory with sporadic, sparse populations of annual canopy kelp. Understory and canopy kelps had affinities with greater bottom structure, and annual kelp density was greatest during periods with higher temperatures. Hexagrammids, especially kelp greenlings, existed year-round in the more structurally complex beds and were typically more abundant during periods with higher temperatures, and at sites with denser annual kelp populations. Most other fishes were transient and generally present only during summer months. Monthly changes in kelp and fish communities reflected a strong seasonal component.
    • Kelp forests and barren grounds: phlorotannin production and holdfast community structure in the Aleutian dragon kelp, Eualaria fistulosa

      Schuster, Martin D.; Konar, Brenda; Iken, Katrin; Coyle, Kenneth (2012-12)
      The canopy forming kelp Eualaria fistulosa inhabits two organizational states throughout the Aleutian archipelago, kelp forests and barren grounds. Urchin abundance and behavior determines which state dominates in any given area. Sporophyll phlorotannin content and holdfast epibiont fauna were investigated at multiple islands along the Aleutian archipelago to determine how the organizational state affects the production of secondary metabolites and the taxon richness, abundance and biomass of holdfast communities. Barren ground sporophylls had higher phlorotannin content than kelp forest sporophylls, although grazing rates on sporophylls from each state did not differ during in situ grazing experiments. The taxon richness, abundance and biomass of holdfast communities were similar between kelp forests and barren grounds at all islands, although these communities varied among islands and were mostly driven by holdfast volume. These results suggest that physical differences such as light and nutrient availability in the kelp forest structure between organizational states may be responsible for differences in phlorotannin content, but that these differences are not reflected in the holdfast community structure. It appears that barren ground holdfast communities are remnants of a once forested area.
    • 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.
    • 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.
    • Metabolic hormone levels and immunocompetence of neonatal harbor seals (Phoca vitulina) in rehabilitation settings compared to wild harbor seal pups

      O'Neil, Danielle Renee (2005-08)
      Health of harbor seal pups in rehabilitation and in the wild were compared using two metabolic hormones (cortisol and total thyroxine, TT4), two cellular immunity components (lymphocytes and eosinophils) and morphometric measurements. Neonatal harbor seals in two rehabilitation facilities were compared to wild harbor seal pups. Permanently captive harbor seals housed at the Alaska SeaLife Center were also studied. High levels of cortisol at weaning suggest changes in the stress response may be due to diet adjustments in pups during rehabilitation. The lower cortisol concentrations post-weaning suggest that pups in rehabilitation had overcome the challenge of pre-weaning diet, handling or environment and avoided chronic stress. TT4 concentrations were higher in wild pups, likely attributed to a more energetically demanding life in a dynamic environment. The rehabilitated pups showed lower lymphocyte counts and higher eosinophil counts compared to wild pups. Wild harbor seal pups were heavier and longer than post-weaned pups in rehabilitation. Animals in rehabilitation are possibly compromised at stranding, but it is also possible that current rehabilitation practices do not mimic what a healthy pup would receive from maternal investment, thus pups undergoing rehabilitation likely remain smaller and possibly immunologically compromised despite repeated and constant care in rehabilitation.
    • Milk fatty acid composition of perinatal and foraging Steller sea lions: examination from pup stomachs

      Miller, Carlene Nicole; Polasek, Lori K.; Oliveira, Alexandra C. M.; Horstmann-Dehn, Larissa A. (2014-08)
      To investigate the relationship of milk fatty acid composition between perinatal and foraging Steller sea lions and within each maternal state (i.e., perinatal or foraging), milk samples were collected in 2010 and 2011 via gastric intubation from Steller sea lion pups on a small rookery in the central Gulf of Alaska. Subsamples of initial milk samples were taken over four hours post-collection to examine changes of fatty acids within milk over time. Maternal states of lactating females of sampled pups were determined via remotely operated video cameras on the rookery. Fatty acid composition within milk, collected from Steller sea lion pup stomachs, did not change over the four hour post-collection period, and thus milk fatty acids were not modified within milk over time. Milk fatty acid composition between Steller sea lion maternal states was different, and thus can be utilized to distinguish between perinatal and foraging Steller sea lions of the same geographic region. In the absence of direct observations, this study demonstrated the use of a viable method to determine maternal state. Milk fatty acid composition remained relatively constant within perinatal Steller sea lions, suggesting steady mobilization of fatty acids from blubber to milk, and within foraging Steller sea lions, implying females forage in the vicinity of the rookery and on similar prey species. Differences in milk fatty acid composition between maternal states, including differences in the relative percentages of polyunsaturated fatty acids, may have implications for growth and development of offspring. For lactating Steller sea lions, foraging after the perinatal period is important for continued delivery of fatty acids needed by young pups.
    • Molecules to marinescapes: the characterization of microbial life in the Arctic Ocean

      Hassett, Brandon T.; Gradinger, Rolf; Collins, R. Eric; Leigh, Mary Beth; McBeath, Jenifer; Lopez, J. Andres (2016-05)
      Microbes are the base of all marine food webs and comprise >90% of all living biomass in the world’s oceans. Microbial life and functioning in high-latitude seas is characterized by the predominance of unknown species that encode uncharacterized genes, replenish nutrients, and modulate ecosystem health by interfacing with disease processes. This research elucidates eukaryotic microbial diversity and functionality in Arctic and sub-Arctic marine environments by describing the culturable and genetic diversity of eukaryotic microbes and the life histories of marine fungi belonging to the Chytridiomycota. This work includes the description of two new mesomycetozoean species, the assembled and annotated genome of Sphaeroforma sirkka, the first description of a cryptic carbon cycle (the mycoloop) mediated by fungi from any marine environment, and the description of large-scale eukaryotic microbial diversity patterns driven by temperature and latitude in the eastern Bering Sea. These results help establish a valuable baseline of microbial diversity in high latitude seas.
    • Monitoring stress hormones in rehabilitated and captive otariids

      Petrauskas, Lisa (2005-08)
      Cortisol and corticosterone are the primary mammalian stress hormones released in response to a perceived stressor. Cortisol is rapidly metabolized in the blood, while corticosterone is the dominant product in fecal material. Radioimmunoassay procedures to measure fecal corticosterone and serum cortisol in California sea lions were validated, and adrenal response to surgical and non-surgical procedures was assessed. Other objectives included seasonal and behavioral variability in fecal corticosterone concentrations in captive Steller sea lions, as well as adrenal response to various stressors of a rehabilitated Steller sea lion. There was a significant (P ... 0.05) adrenal response for rehabilitated California sea lions that underwent minor invasive surgical procedures. The small sample size in this study allowed the identification of a correlation of season and behavior in three captive Steller sea lions. This study found that peak fecal corticosterone values reflected responses to acute stressors during rehabilitation for a Steller sea lion pup. Overall, fecal corticosterone was an adequate tool for monitoring stress non-invasive1y in California and Steller sea lions. In turn, the results indicate that California sea lions may be a suitable surrogate species to study the adrenal response to more invasive procedures that may be used in Steller sea lions.