Now showing items 1-20 of 1231

    • Mathematical Modeling and Simulation with MATLAB

      Buzby, Megan; Lee, Sheldon (2021)
      This textbook attempts to provide you with an overview of the commonly used basic mathematical models, as well as a wide range of applications. It offers a perspective that brings you back to the modeling process and the assumptions that go into it.
    • Conditions for staggering and delaying outplantings of the kelps Saccharina latissima and Alaria marginata for mariculture

      Raymond, Amy E. T.; Stekoll, Michael S. (Wiley, 2021-08-02)
      We describe a method for production of kelp using meiospore seeding creating flexibility for extended storage time prior to outplanting. One bottleneck to expansion of the kelp farming industry is the lack of flexibility in timing of seeded twine production, which is dependent on the fertility of wild sporophytes. We tested methods to slow gametophyte growth and reproduction of early life stages by manipulating temperature of the kelp Saccharina latissima. Reducing temperature from 12 C to 4 C reduced gametophyte size, sporophyte size, egg production, and sporophyte production and subsequently was the best candidate condition for storage experiments of seeded twine. Next, we examined how storage of Alaria marginata and S. latissima seeded twine at 4 C under differing nutrient concentrations affected the viability of sporelings after being moved into optimal growth conditions. Seeded twine storage at 4 C with no alteration to culturing media showed no negative effects in sporophyte density and sporophyte length for both species. This method for seeded twine storage, “cold banking,” allowed seeded twine storage for at least an additional 36 days compared to standard methods, with a total of 56 days spent in the hatchery providing opportunity for outplanting timing and staggering to enhance aquaculture efficiency.
    • Sediment redistribution beneath the terminus of an advancing glacier, Taku Glacier (T’aakú Kwáan Sít’i), Alaska.

      Zechmann, Jenna M.; Truffer, Martin; Motyka, R. J.; Amundson, Jason M.; Larsen, Christopher F.; la (Cambridge University Press, 2020-12-23)
      The recently-advancing Taku Glacier is excavating subglacial sediments at high rates over multidecadal timescales. However, sediment redistribution over shorter timescales remains unquantified. We use a variety of methods to study subglacial and proglacial sediment redistribution on decadal, seasonal, and daily timescales to gain insight into sub- and proglacial landscape formation. Both excavation and deposition were observed from 2003 to 2015 (2.8 ± 0.9ma−1 to +2.9 ± 0.9ma−1). The observed patterns imply that a subglacial conduit has occupied the same site over the past decade. Outwash fans on the subaerial end moraine experience fluvial sediment reworking almost year-round, with net sediment gain in winter and net sediment loss in summer, and an overall mass gain between 2005 and 2015.We estimate that tens of meters of sediment still underlie the glacier terminus, sediments which can be remobilized during future activity. However, imminent retreat from the proglacial moraine will limit its sediment supply, leaving the moraine vulnerable to erosion by bordering rivers. Retreat into an over-deepened basin will leave the glacier vulnerable to increased frontal ablation and accelerating retreat.
    • Climate-Mediated Changes to Linked Terrestrial and Marine Ecosystems across the Northeast Pacific Coastal Temperate Rainforest Margin

      Bidlack, Allison Lynn; Bisbing, Sarah; Buma, Brian; Diefenderfer, Heida L.; Fellman, Jason B.; Floyd, William C.; Giesbrecht, Ian; Lally, Amritpal; Lertzman, Ken P.; Perakis, Steven S.; et al. (Oxford University Press on behalf of American Institute of Biological Sciences., 2021-02-10)
      Coastal margins are important areas of materials flux that link terrestrial and marine ecosystems. Consequently, climate-mediated changes to coastal terrestrial ecosystems and hydrologic regimes have high potential to influence nearshore ocean chemistry and food web dynamics. Research from tightly coupled, high-flux coastal ecosystems can advance understanding of terrestrial–marine links and climate sensitivities more generally. In the present article, we use the northeast Pacific coastal temperate rainforest as a model system to evaluate such links. We focus on key above- and belowground production and hydrological transport processes that control the land-to-ocean flow of materials and their influence on nearshore marine ecosystems. We evaluate how these connections may be altered by global climate change and we identify knowledge gaps in our understanding of the source, transport, and fate of terrestrial materials along this coastal margin. Finally, we propose five priority research themes in this region that are relevant for understanding coastal ecosystem links more broadly.
    • Ice Nucleation Activity of Perfluorinated Organic Acids.

      Schwidetzky, Ralph; Sun, Yuling; Fröhlich-Nowoisky, Janine; Kunert, Anna T; Bonn, Mischa; Meister, Konrad (ACS Publications, 2021-03-31)
      Perfluorinated acids (PFAs) are widely used synthetic chemical compounds, highly resistant to environmental degradation. The widespread PFA contamination in remote regions such as the High Arctic implies currently not understood long-range atmospheric transport pathways. Here, we report that perfluorooctanoic acid (PFOA) initiates heterogeneous ice nucleation at temperatures as high as −16 °C. In contrast, the eight-carbon octanoic acid, perfluorooctanesulfonic acid, and deprotonated PFOA showed poor ice nucleating capabilities. The ice nucleation ability of PFOA correlates with the formation of a PFOA monolayer at the air−water interface, suggesting a mechanism in which the aligned hydroxyl groups of the carboxylic acid moieties provide a lattice matching to ice. The ice nucleation capabilities of fluorinated compounds like PFOA might be relevant for cloud glaciation in the atmosphere and the removal of these persistent pollutants by wet deposition.
    • Disaccharide Residues are Required for Native Antifreeze Glycoprotein Activity.

      Sun, Yuling; Giubertoni, Giulia; Bakker, Huib J; Liu, Jie; Wagner, Manfred; Ng, David Y W; Devries, Arthur L; Meister, Konrad (ACS Publications, 2021-05-06)
      Antifreeze glycoproteins (AFGPs) are able to bind to ice, halt its growth, and are the most potent inhibitors of ice recrystallization known. The structural basis for AFGP’s unique properties remains largely elusive. Here we determined the antifreeze activities of AFGP variants that we constructed by chemically modifying the hydroxyl groups of the disaccharide of natural AFGPs. Using nuclear magnetic resonance, two-dimensional infrared spectroscopy, and circular dichroism, the expected modifications were confirmed as well as their effect on AFGPs solution structure. We find that the presence of all the hydroxyls on the disaccharides is a requirement for the native AFGP hysteresis as well as the maximal inhibition of ice recrystallization. The saccharide hydroxyls are apparently as important as the acetyl group on the galactosamine, the α-linkage between the disaccharide and threonine, and the methyl groups on the threonine and alanine. We conclude that the use of hydrogen-bonding through the hydroxyl groups of the disaccharide and hydrophobic interactions through the polypeptide backbone are equally important in promoting the antifreeze activities observed in the native AFGPs. These important criteria should be considered when designing synthetic mimics.
    • The protandric life history of the Northern spot shrimp Pandalus platyceros: molecular insights and implications for fishery management.

      Levy, Tom; Tamone, Sherry L; Manor, Rivka; Bower, Esther D; Sagi, Amir (Nature, 2020-01-28)
      The Northern spot shrimp, Pandalus platyceros, a protandric hermaphrodite of commercial importance in North America, is the primary target species for shrimp fisheries within Southeast Alaska. Fishery data obtained from the Alaska Department of Fish and Game indicate that spot shrimp populations have been declining significantly over the past 25 years. We collected spot shrimps in Southeast Alaska and measured reproductive-related morphological, gonadal and molecular changes during the entire life history. The appendix masculina, a major sexual morphological indicator, is indicative of the reproductive phase of the animal, lengthening during maturation from juvenile to the male phase and then gradually shortening throughout the transitional stages until its complete disappearance upon transformation to a female. This morphological change occurs in parallel with the degeneration of testicular tissue in the ovotestis and enhanced ovarian vitellogenesis. Moreover, we obtained the entire mRNA sequence of the yolk protein precursor, vitellogenin, and monitored its transcript levels throughout the entire shrimp life-cycle. Vitellogenin transcript levels in the hepatopancreas increased in the early transitional stage until reaching a peak prior to extruding eggs. Such transcriptomic analyses, coupled with a comprehensive description of the gonad, external sex characters and timing of the reproductive life history of spot shrimps contribute to a better understanding of the hermaphroditic reproduction process in the cold Southeast Alaskan waters. This knowledge can contribute to a revision of current conservation efforts to maintain wild populations sustainable for both commercial and ecological considerations.
    • Tidal Echoes 2021

      Alexander, Rosemarie; Bannerman, Amy; Bergren, Erika; Bowman, Emily; Elliot, William; Florian, Steve; Goodman, Jessy; Kane, Jeremy; Kirsch, Geoff; Lamb, Jonas; et al. (University of Alaska Southeast, 2021)
      Tidal Echoes presents an annual showcase of writers and artists who share one thing in common: a life surrounded by the rainforests and waterways of Southeast Alaska.
    • Find the Good: Unexpected Life Lessons from a Small-Town Obituary Writer

      Lende, Heather (University of Alaska Southeast, 2020-09-30)
      As the obituary writer in a spectacularly beautiful but often dangerous spit of land in Alaska, Heather Lende knows something about last words and lives well lived. Now she is distilled what she is learned about how to live a more exhilarating and meaningful life into three words: find the good. It is that simple--and that hard.
    • Tidal Echoes 2003

      Holloway, Robin; Trincado, Andrea; Andree, Judy; Cohen, Greg; Easley, Alexis; Pentecost, Clarissa; Wall, Emily; McKenzie, Liz (University of Alaska Southeast, 2003)
      Tidal Echoes presents an annual showcase of writers and artists who share one thing in common: a life surrounded by the rainforests and waterways of Southeast Alaska.
    • Tidal Echoes 2020

      Ziegler, Callie; Bergren, Erika; Wall, Emily; Elliot, William; Bannerman, Amy; Trafton, Math; Alexander, Rosemarie; Maier, Kevin; Kane, Jeremy; Zacher, Liz (University of Alaska Southeast, 2020)
      Tidal Echoes presents an annual showcase of writers and artists who share one thing in common: a life surrounded by the rainforests and waterways of Southeast Alaska.
    • Tidal Echoes 2019

      Busby, India; Ziegler, Callie; Wall, Emily; Lamb, Jonas; Elliot, William; Bannerman, Amy; Trafton, Math; Landis, Rod; Alexander, Rosemarie; Neeland, Allison; et al. (University of Alaska Southeast, 2019)
      Tidal Echoes presents an annual showcase of writers and artists who share one thing in common: a life surrounded by the rainforests and waterways of Southeast Alaska.
    • Tidal Echoes 2018

      Rumfelt, Elizabeth; Busby, India; Wall, Emily; Lamb, Jonas; Elliot, William; Trafton, Math; Martin, Mary Catherine; Young, Karragh; Kane, Jeremy; Zacher, Liz; et al. (University of Alaska Southeast, 2018)
      Tidal Echoes presents an annual showcase of writers and artists who share one thing in common: a life surrounded by the rainforests and waterways of Southeast Alaska.
    • Tidal Echoes 2017

      Clark, Maranda; Rumfelt, Elizabeth; Wall, Emily; Lamb, Jonas; Elliot, William; Trafton, Math; Hayes, Ernestine; Chordas, Nina; Martin, Mary Catherine; Enge, Carrie; et al. (University of Alaska Southeast, 2017)
      The 2017 edition of Tidal Echoes presents an annual showcase of writers and artists who share one thing in common: a life surrounded by the rainforests and waterways of Southeast Alaska.
    • Seasonal Characteristics of Humpback Whales {Megaptera novaeangliae) in Southeastern Alaska

      Straley, Janice M.; Gabriele, Christine M.; Baker, C. Scott (National Park Service Alaska System Support Office, 1995-11)
      Humpback whales were studied in southeastern Alaska to assess seasonal distribution and numbers, migration patterns, length of stay, female reproductive histories, and calf survival. A mean annual estimate and 95% confidence interval of whales present in the study areas was 404 ± 54 individuals. The longest length of stay was nearly 7 months, and the shortest transit to the Hawaiian mating and calving grounds was 39 days. Generally, birth intervals did not vary from one calf every two or three years; individual variation ranged from one to five years. There were few resightings of whales first seen as calves. The recovery of North Pacific humpback whales will only occur through an increase in the survival of calves to become sexually mature and reproducing adults.
    • New views of humpback whale flow dynamics and oral morphology during prey engulfment

      Kosma, Madison, M.; Chenoweth, Ellen M.; Straley, Janice M.; Werth, Alexander J. (Marine Mammal Science, 2019-05-14)
      The rise of inexpensive, user-friendly cameras and editing software promises to revolutionize data collection with minimal disturbance to marine mammals. Video sequences recorded by aerial drones and GoPro cameras provided close-up views and unique perspectives of humpback whales engulfing juvenile salmon at or just below the water surface in Southeast Alaska and Prince William Sound. Although humpback feeding is famous for its flexibility, several stereotyped events were noted in the 47 lunges we analyzed. Engulfment was extremely rapid (mean 2.07 s), and the entrance through which the tongue inverts into the ventral pouch was seen as water rushes in. Cranial elevation was a major contributor to gape, and pouch contraction sometimes began before full gape closure, with reverberating waves indicating rebounding flow of water within the expanded pouch. Expulsion of filtered water began with a small splash at the anterior of the mouth, followed by sustained excurrent flow in the mouth’s central or posterior regions. Apart from a splash of rebounding water, water within the mouth was surprisingly turbulence-free during engulfment, but submersion of the whale’s head created visible surface whirlpools and vortices which may aggregate prey for subsequent engulfment.
    • Exploring variability in the diet of depredating sperm whales in the Gulf of Alaska through stable isotope analysis

      Wild, Lauren A.; Mueter, Franz; Witteveen, Briana H.; Straley, Janice M. (The Royal Society Publishing, 2020-01-27)
      Sperm whales interact with commercially important groundfish fisheries offshore in the Gulf of Alaska (GOA). This study aims to use stable isotope analysis to better understand the trophic variability of sperm whales and their potential prey, and to use dietary mixing models to estimate the importance of prey species to sperm whale diets. We analysed tissue samples from sperm whales and seven potential prey (five groundfish and two squid species). Samples were analysed for stable carbon and nitrogen isotope ratios, and diet composition was estimated using Bayesian isotopic mixing models. Mixing model results suggest that an isotopically combined sablefish/ dogfish group, skates and rockfish make up the largest proportion of sperm whale diets (35%, 28% and 12%) in the GOA. The top prey items of whales that interact more frequently with fishing vessels consisted of skates (49%) and the sablefish/dogfish group (24%). This is the first known study to provide an isotopic baseline of adult male sperm whales and these adult groundfish and offshore squid species, and to assign contributions of prey to whale diets in the GOA. This study provides information to commercial fishermen and fisheries managers to better understand trophic connections of important commercial species.
    • Humpback whales feed on hatchery-released juvenile salmon

      Chenoweth, Ellen M.; Straley, Janice M.; McPhee, Megan V.; Atkinson, Shannon; Reifenstuhl, Steve (The Royal Society Publishing, 2017-06-07)
      Humpback whales are remarkable for the behavioural plasticity of their feeding tactics and the diversity of their diets. Within the last decade at hatchery release sites in Southeast Alaska, humpback whales have begun exploiting juvenile salmon, a previously undocumented prey. The anthropogenic source of these salmon and their important contribution to local fisheries makes the emergence of humpback whale predation a concern for the Southeast Alaska economy. Here, we describe the frequency of observing humpback whales, examine the role of temporal and spatial variables affecting the probability of sighting humpback whales and describe prey capture behaviours at five hatchery release sites. We coordinated twice daily 15 min observations during the spring release seasons 2010–2015. Using logistic regression, we determined that the probability of occurrence of humpback whales increased after releases began and decreased after releases concluded. The probability of whale occurrence varied among release sites but did not increase significantly over the 6 year study period. Whales were reported to be feeding on juvenile chum, Chinook and coho salmon, with photographic and video records of whales feeding on coho salmon. The ability to adapt to new prey sources may be key to sustaining their population in a changing ocean.
    • Summit: The UAS Writing Center's Collection of Exceptional Academic Works for 2020/2021

      Billings, Rayne; Brend, Olive; Goodman, Jessy; Cruz, Celestina; Erickson, Anastasia; Hein, Berni; Hoagland, James; File, Braden; Steiner, Alicia; File, Braden; et al. (University of Alaska Southeast Writing Center, 2021)
      We at the UAS Writing Center are once again pleased to announce the completion of the second edition of our undergraduate academic writing journal, Summit: The UAS Writing Center’s Collection of Exceptional Academic Works for 2020/2021. This year’s edition is dedicated to Allison Neeland, our past Specialist, for all her support and dedication to the Writing Center. We also extend a hearty congratulation to UAS senior Celestina Cruz for winning the 2020/2021 Ernestine Hayes Award for Excellence in Academic Writing. Also included in the journal are the works of five other student writers: Rayne Billings, Anastasia Erickson, Berni Hein, James Hoagland, and Alicia Steiner. Thank you to everyone who submitted, to our panel of faculty and student judges, to Diersen Bankert for creating this year’s stunning cover, to Student Government for funding the prize money, and to everyone else who has supported this publication.
    • Pectoral herding: an innovative tactic for humpback whale foraging

      Kosma, Madison, M.; Werth, Alexander J.; Szabo, Andrew R.; Straley, Janice M. (The Royal Society, 2019-09-23)
      Humpback whales (Megaptera novaeangliae) have exceptionally long pectorals (i.e. flippers) that aid in shallow water navigation, rapid acceleration and increased manoeuvrability. The use of pectorals to herd or manipulate prey has been hypothesized since the 1930s. We combined new technology and a unique viewing platform to document the additional use of pectorals to aggregate prey during foraging events. Here, we provide a description of ‘pectoral herding’ and explore the conditions that may promote this innovative foraging behaviour. Specifically, we analysed aerial videos and photographic sequences to assess the function of pectorals during feeding events near salmon hatchery release sites in Southeast Alaska (2016–2018). We observed the use of solo bubble-nets to initially corral prey, followed by calculated movements to establish a secondary boundary with the pectorals—further condensing prey and increasing foraging efficiency. We found three ways in which humpback whales use pectorals to herd prey: (i) create a physical barrier to prevent evasion, (ii) cause water motion to guide prey towards the mouth, and (iii) position the ventral side to reflect light and alter prey movement. Our findings suggest that behavioural plasticity may aid foraging in changing environments and shifts in prey availability. Further study would clarify if ‘pectoral herding’ is used as a principal foraging tool by the broader humpback whale population and the conditions that promote its use.