• 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.
    • The Influence Of Estuarine Habitats On Expression On Life History Characteristics Of Coho Salmon Smolts In South-Central Alaska

      Hoem Neher, Tammy D.; Rosenberger, Amanda; McPhee, Megan; Mueter, Franz; Zimmerman, Christian (2012)
      Expression of traits that lead to life history diversity in salmonids may provide population-level resilience and stability in dynamic environments. I examined habitat use and variability in life history trait expression in juvenile coho salmon Oncorhynchus kisutch occupying two contrasting estuary environments in south-central Alaska. My goal was two-fold: first, to determine if salmon were using estuaries as rearing environments and were therefore potentially vulnerable to selection pressures within; and second, to compare traits of salmon that reared in contrasting estuary environments to explore the potential for differential trait expression related to estuary size and habitat complexity differences. Juvenile coho salmon reared in estuaries for extended periods of time and patterns of use corresponded to environmental conditions within the estuaries. Populations using adjacent but contrasting estuary environments exhibited differential trait expression and were genetically distinct. My work highlights how pristine, functioning estuary habitats contribute to resilience of salmon populations to environmental changes in two ways: first, by providing habitats for individuals to increase in size and condition prior to ocean entry; and second, by providing for alternative life history tactics (providing quality habitat to delay marine entry times and increase body size). Management approaches for resilient salmon runs must therefore maintain both watershed and estuary function.
    • 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.
    • The Influence Of Water Velocity And Depth On Prey Detection And Capture By Juvenile Coho Salmon And Steelhead: Implications For Habitat Selection And Segregation

      Piccolo, John J.; Hughes, Nicholas F. (2005)
      I studied the effects of water velocity and depth on drift-foraging by juvenile coho salmon and steelhead to assess how these influence their reported habitat segregation into pools and riffles, respectively. I used three-dimensional video analysis of stream-tank foraging experiments to test how velocity and depth influence prey capture probabilities, and the geometry and dynamics of prey detection and capture. I used the experimental results to develop net energy intake models to predict optimal foraging velocities for coho and steelhead. Prey capture probabilities for both coho and steelhead declined from $65% to 10% with an increase in velocity from 0.29 to 0.61 m · sec -1, with little difference between the species. Capture maneuver characteristics were similar for both species, including reduced prey detection distance and capture probabilities within the capture area, constant prey interception speed, and increasing return speed. I conclude that faster velocity reduces prey capture success by coho and steelhead, but that differences in capture abilities are not responsible for habitat segregation. Prey capture probabilities for both species were constant at ~40% at depths from 0.15 to 0.60 m, with little difference between the species. Capture maneuver characteristics were similar for both species, including increased prey detection distance and interception speed, and constant return speed. I predict that prey capture rate increases proportionally to water depth for coho and steelhead, but that differences in capture probabilities are not responsible for habitat segregation. I used the experimental results to develop net energy intake models that predicted optimum foraging velocities of 0.29 m · s-1 for coho and 0.30 m · s-1 steelhead. Modeled 10% and 25% increases in swimming costs for coho reduced optimum velocity by 0 and 0.01 m · s-1, respectively. These results, coupled with those from the depth experiments, suggest that habitat segregation may be due to factors other than short-term foraging considerations. I propose that these are largely selective mechanisms such as size-based habitat selection, differences in growth trajectories, or prey specialization. I do not discount the possibility that interactive mechanisms are also important, especially at periods of high fish density or limited prey availability.
    • The Role Of Copepods In The Distribution Of Hydrocarbons: An Experimental Approach

      Duesterloh, Switgard; Shirley, Thomas C. (2002)
      Copepods may provide a significant pathway for the concentration and transfer of polyaromatic compounds (PAC) to higher trophic level consumers. PAC dissolved from weathered crude oil are more persistent in the environment and have much higher toxicity than the lighter, more volatile fractions of crude oil. Because of their polarity, PAC tend to accumulate in bio-lipids. Subarctic copepod species can contain up to 80% of their body dry weight in lipids and have a high surface area to volume ratio. Thus, PAC accumulation is rapid and bioaccumulation factors are in the order of 500--8000, depending upon species and lipid content. While direct toxic effects of oil on copepods have been reported in the order of 10 mg/L, toxicity increases substantially in the presence of natural ultraviolet (UV) radiation. Phototoxic effects to the copepods Calanus marshallae and Metridia okhotensis were observed at concentrations of ~2mug/L total dissolved PAC followed by 4--8 hours of exposure to ambient daylight. Responses included mortality, immobilization and discoloration of lipid sacs. Further experiments were conducted to test the interaction effects of various concentrations of PAC dissolved from weathered Alaska North Slope crude oil and subsequent exposure to sunlight with and without the UVB component to the copepods Neocalanus flemingeri and N. plumchrus. Phototoxicity was found to be a linear function of the product of light intensity and PAC concentration. High natural variability in egg production rates precluded significant results of the toxicity of oil to copepod reproduction. This work has shown that copepods could potentially provide a mechanism for the concentration of dissolved PAC from the water and its transfer into pelagic and benthic food chains.
    • Thermal limitations on chinook salmon spawning habitat in the northern extent of their range

      Decker, Samantha Kristin Strom; Margraf, F. Joseph; Rosenberger, Amanda; Evenson, Matthew (2010-05)
      Pacific salmon (Oncorhynchus) habitat models attempt to balance research efficiency with management effectiveness, however, model transferability between regions remains elusive. To develop efficient habitat models, we must understand the critical elements that limit habitat. At the northern edge of the geographic range for Chinook salmon, O. tschawytscha, water temperature is a probably a limiting habitat factor. This study investigated the spatial and temporal correspondence between water temperature and Chinook salmon spawning on the Chena River, Alaska. Water temperatures were monitored at 21 stations across 220 river kilometers during the 2006 and 2007 spawning seasons and compared to known thermal requirements for egg development. While an absolute upstream thermal boundary to spawning was not discovered, we describe potential temporal limitations in thermal conditions over the spawning season. Our results show that 98.5% of Chinook salmon selected spawning habitat in which their eggs have a 90% probability of accumulating 450 ATUs before freeze up. This suggests not only temperature conditions limit salmon spawning habitat, but also, as expected, water temperatures temporally limit accessible Chinook salmon spawning habitat at the northern edge of their range. This project documents new spawning habitat for the Anadromous Waters Catalog and broadens the geographical range of Chinook salmon thermal habitat research. It also contributes to the understanding of the processes that define salmon habitat, while providing a baseline for further investigations into water temperature in other thermal regimes.
    • Thyroid hormone binding to brain nuclear extracts during smoltification in coho salmon

      Cheek, L. Michael (1991)
      Salmon complete a metamorphosis called smoltification prior to entering salt water. Increased thyroid activity, olfactory imprinting, and chemical and structural changes in the brain are known to occur at this time. This study was undertaken to determine if triiodothyronine (T$\sb3$) binding to brain nuclear extracts changes during smoltification. During this investigation serum thyroxine (T$\sb4$) concentrations increased three fold during smoltification coincident with changes in coloration and morphology and surged again during downstream migration to six times presmolt concentrations. Using ultrafiltration assays, homologous displacement experiments of KCl extracts of recovered brain cell nuclei indicated that maximal binding capacity increased during smoltification and down-stream migration. The increase in receptor concentration lagged the increase in serum thyroxine by one week. Dissociation constants increased during smolt transformation but declined abruptly during down-stream migration. However, dissociation constants did not change during smoltification if nuclear extracts had been previously incubated at room temperature to remove endogenous ligand. Dissociation rate increased significantly, coincident with the increase in receptor concentration measured by homologous displacement. The maximal probable percent occupancy of available receptors increased from 60% before to greater than 95% during the smolt transformation climax. These results provide evidence that thyroid hormone receptors participate in brain development and olfactory imprinting in smolting salmon.
    • To pup or not to pup? Using physiology and dive behavior to answer the Weddell Seal's overwinter question

      Shero, Michelle R.; Mellish, Jo-Ann; Burns, Jennifer; Hardy, Sarah; Costa, Daniel; Buck, C. Loren (2015-08)
      Female Weddell seals (Leptonychotes weddellii) haul-out on the fast-ice surrounding the Antarctic continent in October and November each year to give birth to and nurse their pups. Breeding follows directly after weaning (December) and the annual molt begins in January-February. Animals reduce foraging efforts during the lactation and molting periods, but very little is known regarding the influence of this reduced activity on physiological condition. After a period of embryonic diapause, the annual molt coincides with embryo attachment and the start of active gestation. Consequently, female physiological condition at this time may influence reproductive success the following year. Overall female health and the ability to forage successfully throughout the gestation period (austral winter) may impact the likelihood that a pregnancy is brought to term. Therefore, this study tested whether overwinter changes in Weddell seal physiology and foraging efforts are reflected in reproductive outcomes the following year (i.e., to answer the over winter question of "to pup or not to pup?"). From 2010-2012, 100 (January-February: n = 53; October-November: n = 47) adult female Weddell seals were captured in Erebus Bay, Antarctica to assess overwinter changes in physiological condition and/or dive behavior that may be associated with reproductive success. Morphometric measurements and isotopic dilution procedures revealed that female Weddell seals gain ~10-15% of their body mass across the winter period, primarily in the form of blubber and lipid mass. The proportion of mass and lipid gain was similar regardless of whether females returned the following year and successfully gave birth, or did not produce a pup. Further, the amount of mass and energy acquired across gestation in the Weddell seal was markedly less than previously reported for other phocid species. Despite changes in activity patterns and body composition, Weddell seals maintained blood hemoglobin and muscle myoglobin concentrations across the winter. Therefore, Weddell seal total body oxygen stores and calculated aerobic dive limit (cADL) were conserved. This ensures that females have the physiological capabilities to effectively forage directly following the annual molt when they are at their leanest and must regain body mass and lipid stores. Although aerobic capacities did not change, dive effort varied considerably throughout the austral winter. Proxies of dive effort (duration, depth, %dives > cADL) were highest just after the molt (January-February) and just prior to the subsequent pupping season (August-September). Additionally, the proportion of each day spent diving increased mid-winter. Females that were observed the following year with a pup significantly increased all indices of foraging effort during the austral winter as compared to females that returned without a pup. This study is the first to identify and measure differences in dive efforts due to reproductive status, and indicates that successful reproduction is associated with greater foraging effort.
    • Toothed whale interactions with longline fisheries in Alaska

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

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

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

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

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

      Wang, Shiway; 王小葳; Wooller, Matthew; Budge, Suzanne; Horstmann-Dehn, Lara; Iken, Katrin; Springer, Alan (2014-08)
      Marine production across the Bering-Chukchi continental shelf is influenced by seasonal sea ice dynamics and climatic conditions. Of particular importance is variability in the magnitude and timing of annual phytoplankton production in the water column and in sea ice, and effects of such variability on food web composition and productivity. Of primary concern is the long-term effect of the projected loss of Arctic sea ice on ecosystem productivity and stability, and the fate of upper trophic level species. I examined a portion of the Bering-Chukchi Sea food web by analyzing the fatty acid composition and stable carbon isotope ratios of individual fatty acids in particulate organic matter from sea ice and the water column. These techniques were used to make inferences about diets of three species of zooplankton (Themisto libellula, Calanus marshallae/glacialis, Thysanoessa raschii) sampled during a recent climatically cold, relatively heavy sea ice period in the Bering Sea. I also analyzed fatty acids of four species of ice-associated seals--ringed (Pusa/Phoca hispida), bearded (Erignathus barbatus), spotted (Phoca largha), and ribbon seals (Histriophoca fasciata)--sampled during the same relatively cold period (2007-2010) as well as a preceding warm (2002-2005), relatively low sea ice period in the Bering Sea. Particulate organic matter from sea ice and the water column had different fatty acid characteristics, most likely stemming from differences in algal composition. My results also showed that in the Bering Sea cold period, the amphipod T. libellula was predominately carnivorous, and the copepod C. marshallae/glacialis and euphausiid T. raschii were primarily herbivorous, but displayed some degree of omnivory. Across all years (2002-2010), fatty acid composition of ice seals showed clear evidence of resource partitioning among them, and little niche separation between spotted and ribbon seals, which is consistent with previous studies. The fatty acid composition of primarily pelagic feeding adult ringed seals and predominantly benthic feeding adult bearded seals did not differ between the recent warm (2002-2005) and cold (2007-2010) periods in the Bering Sea, suggesting that their diets and possibly food web structures were not affected by these large multiyear environmental fluctuations. Notably however, the stable carbon isotope ratios of individual fatty acids of bearded seals from the Bering Sea cold period were higher than those from the warm period, which suggests that their prey base in the Bering Sea was receiving more input from particulate organic matter from sea ice than the water column during those years. By using the stable carbon isotope ratios of individual fatty acids of particulate organic matter from sea ice and the water column in a series of stable isotope mixing models, I estimated the proportional contribution of fatty acids from sea ice particulate organic matter in T. libellula, C. marshallae/glacialis, and T. raschii collected in 2009 and 2010 as 36-72%, 27-63%, and 39-71%, respectively. Using a similar set of mixing models, I estimated that adult bearded seals had the highest level of fatty acids from sea ice particulate organic matter (62-80%), followed by spotted seals (51-62%), and then ringed seals (21-60%) in 2009 and 2010. Although estimates could not be made for ribbon seals due to lack of samples in 2009 and 2010, their stable carbon isotope ratios of individual fatty acids from 2003 were very similar to those of spotted seals suggesting that the proportional contribution of fatty acids from sea ice particulate organic matter to ribbons seals was similar to that of spotted seals. Assuming that seals sourced their sympagic fatty acids from the Bering Sea, these results suggest that sympagic production is currently an important contributor to food webs supporting both benthic and pelagic upper trophic level species in years with heavy ice cover in the Bering Sea. Thus, the question is raised--with the projected continuing loss of seasonal sea ice in the Arctic, will organic matter input from sympagic production also decline, and will it be compensated for by pelagic production to balance both pelagic and benthic carbon and energy budgets?
    • Traditional knowledge and fish biology: a study of Bering cisco in the Yukon River Delta, Alaska

      Runfola, David Michael; Sutton, Trent; Carothers, Courtney; Norton, David W.; Schneider, William (2011-05)
      Relatively little is known about the biology of whitefishes (subfamily Coregoninae) in Alaska. To address this shortcoming, I combined social and biological science methods to examine whitefish in the Yukon River delta, Alaska. This study had two objectives: (1) to collaborate with Yup'ik subsistence fishers in sharing their knowledge of whitefish; and (2) to describe the life history of Bering cisco Coregonus laurettae. In August 2004, interview participants discussed Yup'ik traditional knowledge of whitefish. Participants shared knowledge of Bering cisco and other whitefish species. Interviews demonstrated the need for greater awareness of traditional knowledge, and the importance of communicating this knowledge with scientists. In addition, 120 Bering ciscoes were collected in August 2005 and 2006 with gill nets in the Yukon River delta, Alaska. Bering ciscoes ranged in fork length from 146 to 490 mm (mean = 321 mm) and in weight from 32 to 735 g (mean = 304 g). Fish ranged in age from 0 to 6, with one age-11 individual observed. Diet analysis showed that Bering ciscoes fed primarily on sticklebacks. My study records important social and biological data regarding Bering cisco, linking ethnography and fish biology as a means of investigating this poorly understood species.
    • Transport of dungeness crab (Cancer magister) megalopae into Glacier Bay, Alaska

      Herter, Heidi L.; Eckert, Ginny L.; Shirley, Thomas; Taggart, Spencer (2007-05)
      Areas of high Cancer magister larval recruitment and transport mechanisms were identified in the lower portion of Glacier Bay, Alaska. Megalopae were collected at three sites in 2004 and 2005 using light traps positioned within 1 m of the surface and bottom at 10 m depth. Surface traps captured 96.5 - 99.4 % of megalopae collected. Megalopae abundances were highly pulsed and decreased with increasing distance from the mouth of Glacier Bay. Spatial variation was similar between years with significant differences among all sites in 2005. Half of the total annual megalopae supply occurred over just two nights in September or October, the dates of which varied by location. Megalopae abundance in Bartlett Cove was negatively cross-correlated with tidal amplitude at -3 to + 1 d lags and positively cross-correlated with maximum wind speed at a 0 d lag. Megalopae abundance in the South Beardslee Islands was positively correlated with tidal amplitude and negatively correlated with maximum wind speed at +2 to +3 d lags. Abundance in the North Beardslee Islands was low and not correlated with tides or winds. Spatial variation in megalopae abundance and correlations between abundances and transport processes suggests that Dungeness crab megalopae are transported into Glacier Bay.
    • Trophic dynamics and stock characteristics of snow crabs, Chionoecetes opilio, in the Alaskan Arctic

      Divine, Lauren Mallory; Iken, Katrin; Bluhm, Bodil A.; Lovvorn, James R.; Kruse, Gordon H.; Mueter, Franz J. (2016-08)
      Arctic waters off the coast of Alaska have become increasingly open to human activities via dramatic climatic changes, such as reduced sea ice thickness and extent, warming ocean temperatures, and increased freshwater input. This research advances knowledge of snow crab trophic dynamics and stock characteristics in Arctic waters off the Alaska coast. Here, I provided baseline information regarding snow crab position in Beaufort Sea benthic food webs, its specific dietary habits in the Chukchi and Beaufort seas, and expanded upon previously limited life-history and population dynamic data in the Chukchi and Beaufort seas. I first detailed benthic food webs on the Alaskan Beaufort Sea shelf and snow crab trophic positions within these food webs using stable δ¹³C and δ¹⁵N isotope analysis. Water column and sediment particulate organic matter (POM) were used as primary food web end members. Isotopic niche space (δ¹³C – δ¹⁵N) occupied by benthic taxa provided measures of community-wide trophic redundancy and separation. Water column and sediment POM δ¹³C values generally reflected terrestrial POM inputs in the eastern and central shallow (14-90 m) Beaufort regions, but were indicative of persistent marine influence in the western and central deep (100-220 m) regions. Food web structure, as reflected by consumer trophic levels (TLs), trophic redundancy, and trophic niche space, supported the POM findings. In the eastern and central shallow regions, consumers occupied mainly lower TL (TL= 1-3), whereas consumers in the western regions occupied intermediate and higher TL (TL= 3-4). Overall trophic redundancy and niche space occupied by food webs in these four regions, however, was similar. The central deep Beaufort food web was unique in all metrics evaluated, and the comparatively largest isotopic niche space, with high trophic niche separation but low trophic redundancy, suggests that this region may be most vulnerable to perturbations. Snow crabs occupied food webs in the central deep and western shallow and deep Beaufort regions, where they maintained a consistent TL of 4.0 across regions. I then investigated snow crab dietary habits across the Chukchi, and the Alaskan and Canadian Beaufort seas in the size range of 40 to 130 mm CW using stomach contents and stable isotope analyses. Snow crabs consumed four main prey taxa: polychaetes, decapod crustaceans (crabs, amphipods), echinoderms (mainly ophiuroids), and mollusks (bivalves, gastropods). Crab diets in the southern and northern Chukchi Sea regions were similar to those in the western Beaufort Sea in that bivalve, amphipod, and crustacean consumption was highest. The Canadian Beaufort region was most unique in prey composition and in stable isotope values. Cannibalism on snow crabs was higher in the Chukchi Sea regions relative to the Beaufort Sea regions, suggesting that cannibalism may have an impact on recruitment in the Chukchi Sea via reduction of cohort strength after settlement to the benthos, as known from the Canadian Atlantic. Based on a comparison with southern Chukchi Sea macrofauna data, these results document the non-selective, omnivorous role of snow crabs across the entire Pacific Arctic, as well as providing first evidence for cannibalism in the Chukchi Sea. Finally, I generated new estimates of stock biomass, abundance, and maximum sustainable yield, length-weight relationships, size-at-maturity, and fecundity of snow crab in the Alaskan Arctic. Although snow crabs were more abundant in the Chukchi Sea, no crabs larger than the minimum marketable size (> 100 mm carapace width, based on Bering Sea metric) occurred in this region. Harvestable biomass of snow crabs only occurred in the Beaufort Sea, but was considerably lower than previous estimates in the Arctic FMP. Length-weight relationships were generally similar for male and female snow crabs between the Chukchi and Beaufort seas. Size-at-maturity and female fecundity in the Chukchi Sea were similar to snow crabs occurring in other geographic regions; low sample sizes in the Beaufort prevented size-at-maturity and fecundity analysis. Together these results contribute new understanding of Arctic snow crab population dynamics by utilizing a rich dataset obtained recently from the Chukchi and Beaufort regions.
    • Trophic dynamics of pinniped populations in Alaska using stable carbon and nitrogen isotope ratios

      Hirons, Amy Christia; Schell, Donald; Castellini, Michael; Cooney, Theodore; Springer, Alan; Barry, Ronald (2001-05)
      Trophic changes in populations of Stellar sea lions (Eumetorias jubatus), northern fur seals (Callorhinus ursinus) and harbor seals (Phoca vitulina) in the eastern Bering Sea and Gulf of Alaska were studied using stable isotope analysis. Declining populations of all three species of pinnipeds prompted this study to determine if changes in diet, likely resulting from food limitation, contributed to the declines. Stable carbon and nitrogen isotope ratios were analyzed in the vibrissae (whiskers) and body tissues of pinnipeds from 1993-1998 and compared with muscle tissue from prey species during the same time period to determine pinniped trophic dynamics. Vibrissae growth rate studies revealed harbor seal vibrissae are only retained for one year and then replaced, while Steller sea lions maintain their vibrissae for several years. Isotopic data from all three species are consistent with diets composed of walleye pollock (Theragra chalcogramma) at various times and locations throughout the year. Steller sea lion and northern fur seal vibrissae revealed regular oscillations along their lengths in both carbon and nitrogen isotope ratios that likely corresponded to regional isotopic differences. As these animals moved or migrated from one region to another during the year, they metabolically incorporated the different regional isotope ratios through their prey. Because these animals return to their rookery to pup, breed and molt each year, the isotope ratios in the vibrissae showed a regular pattern of enrichment and deplection. Harbor seals, which tend to stay in one geographic location, have relatively static isotope ratios in their vibrissae, while seals that moved into offshore waters had fluctuating isotope ratios that corresponded to regional difference. No trophic shifts, as evidenced by major changes in nitrogen isotope ratios, were present in any tissues from the three species over the period 1975-1998. Stable isotope ratios of bone collagen for all three species from 1950-1997 indicated no change in trophic level but did reveal that the seasonal primary production in the North Pacific Ocean has declined and may have contributed to a decreased carrying capacity impacting these top trophic organisms
    • Trophic ecology of nearshore fishes in glacially-influenced estuaries of Southeast Alaska

      Whitney, Emily Jean; Beaudreau, Anne H.; Bergstrom, Carolyn A.; Howe, Emily R. (2016-08)
      Estuaries in Southeast Alaska (SEAK) are linked to terrestrial ecosystems by the flow of freshwater from plentiful precipitation and glacial runoff. This thesis examined the trophic ecology of nearshore fishes in SEAK estuaries to advance our understanding of how deglaciation and resulting shifts in the timing and magnitude of freshwater runoff will affect estuarine food webs. The goals of this work were to characterize seasonal variation in the feeding ecology of an abundant estuarine predator across three glacially-influenced sites and to examine the relative contribution of organic matter (OM) from terrestrial-riverine sources to the diets of estuarine consumers. In chapter one, stomach contents of Pacific staghorn sculpin (Leptocottus armatus) were analyzed to test the hypothesis that diets would differ across sampling sites and months, reflecting variation in freshwater runoff and the phenology of estuarine organisms. Stomach contents of staghorn sculpins were collected monthly between April and September 2014, from intertidal sites at mouths of rivers that differ in their headwater hydrology. Staghorn sculpins consumed a variety of prey, including gammarids, mysids, isopods, polychaetes, and other freshwater-tolerant prey, as well as juvenile fish. Weak to moderate differences observed in diet composition across sites and months likely reflected spatial and seasonal shifts in the occurrence of freshwater-tolerant invertebrates and young-of-the-year fishes. Overall, the ability of staghorn sculpins to take advantage of a variety of prey across variable conditions may make them resilient to environmental change. In chapter two, I examined trophic linkages between terrestrial and marine food webs by using stable isotope analysis to evaluate the relative contribution of terrestrial-riverine OM to the diets of estuarine consumers. Analyses showed limited use of terrestrial-riverine OM by marine fishes (Leptocottus armatus and Platichthys stellatus) and more variable use by anadromous fishes (Salvelinus malma and Oncorhynchus kisutch). Intertidal invertebrates used more terrestrial-riverine OM than fish, with greater use of allochthonous OM earlier in the summer. Despite the documented availability of terrestrial-riverine OM, estuarine consumers showed limited use of this resource. These findings inform our baseline understanding of trophic linkages in glacially-influenced estuaries, a critical first step in evaluating future climate driven changes to coastal ecosystems.