• Brucella suis type 4 in foxes and their role as reservoirs/vectors among reindeer

      Morton, Jamie Kay; Williamson, Francis S. L. (1989)
      Field and laboratory studies were conducted to test the hypotheses that (1) the reindeer/caribou organism, Brucella suis type 4, is incidentally transmitted to reindeer predators such as foxes but does not cause reproductive disease in them, and (2) infected predators such as foxes are terminal hosts and do not serve as reservoirs of infection for reindeer. In field collections, serologic prevalence of brucellosis was similar for male and female foxes (Vulpes vulpes and Alopex lagopus). B. suis type 4 was isolated from female Vulpes and Alopex. No association between reproductive status of foxes and brucellosis infections was observed. Serologic titers in Vulpes experimentally infected by oral exposure to Brucella suis type 4 were detected first by the standard tube and plate agglutination tests which were followed by the buffered Brucella antigen, rivanol, and complement fixation tests. Brucella suis type 4 was isolated from the feces 4 to 6 days post-exposure (PE) and from the oral cavity for as long as 3 weeks PE in Vulpes challenged with 10$\sp9$ or 10$\sp{11}$ colony forming units. Brucella suis type 4 was isolated frequently from regional lymph nodes in the head up to 18 weeks PE, and from only more distant nodes at 22 and 66 weeks PE. Organisms did not localize in the reproductive tract. Clinical effects of brucellosis in Vulpes experimentally-infected were not observed. Pathologic lesions were not detected in the male and non-gravid female reproductive tract. Due to breeding failure, effects of Brucella suis type 4 on the pregnant fox reproductive tract were not determined in experimental infections. Gross and microscopic pathology was limited to lymph nodes. Fox to fox transmission attributed to aerosols from products shed by infected foxes occurred readily. Transmission from Vulpes to lemmings (Dicrostonyx rubricatus) that were exposed to urine from infected fox occurred frequently. Transmission from infected Vulpes to two reindeer (Rangifer tarandus) occurred under conditions of close confinement. Ingestion of organisms passed mechanically in the fox feces was considered the probable source of infection. Fox saliva containing Brucella was also implicated in transmitting the organism through bites or aerosols.
    • Building a toolset for fuel cell turbine hybrid modeling

      Burbank, Winston S. (2006-12)
      Fuel cell/gas turbine hybrids show promise of high efficiency power generation, with electrical efficiencies of 70% or better shown by modeling, although these efficiency levels have not yet been demonstrated in hardware. Modeling of such systems is important to optimize and control these complex systems. This work describes a modeling tool developed to examine steady-state operation of different hybrid configurations. This model focuses on the area of compressor-turbine modeling, which is a key component of properly controlling fuel cell/gas turbine hybrids. Through side-by-side comparisons, this model has been tested and verified by Dr. Wolf of Brayton Energy [1]. This modeling tool will be used in further work to evaluate various configurations of turbines and fuel cells in hybrid configurations, focusing on both the performance and cost of such systems.
    • Building Blocks Of Self -Organized Criticality

      Woodard, Ryan; Newman, David (2004)
      Why are we having difficulty developing economical nuclear fusion? How can a squirrel cause a statewide power blackout? How do correlations arise in a random complex system? How are these questions related? This thesis addresses these questions through a study of self-organized criticality (SOC). Among the systems that have been proposed as SOC are confined fusion plasmas, the Earth's magnetosphere and earthquake faults. SOC describes how large-scale complex behavior can emerge from small-scale simple interactions. The essence of SOC is that many dynamical systems, regardless of underlying physics, share a common nonlinear mechanism: local gradients grow until exceeding some critical gradient and then relax in events called avalanches. Avalanches range in size from very small to system-wide. Interactions of many avalanches over long times result in robust statistical and dynamical signatures that are surprisingly similar in many different physical systems. Two of the more well-known signatures are power law scaling of probability distribution functions (PDFs) and power spectra. Of particular interest in the literature for approximately a century are 1/f spectra. I studied the SOC running sandpile model and applied the results to confined and space plasmas. My tools were power spectra, PDFs and rescaled range ( R/S) analysis. I found that SOC systems with random external forcing store memory of previous states in their local gradients and can have dynamical correlations over very long time scales regardless of how weak the external forcing is. At time scales much longer than previously thought, the values of the slope of the power spectra, beta and the Hurst exponent, H, are different from the values found for white noise. As forcing changes, beta changes in the range 0.4 <math> <f> &lap;</f> </math> beta &le; 1 but the Hurst exponent remains relatively constant, H &ap; 0.8. The same physics that produces a 1/f spectrum at strong forcing produces a f -0.4 spectrum at weaker forcing. Small amounts of diffusive spreading added to the two dimensional SOC sandpile greatly decreases the frequency and maximum size of large transport events. More diffusion increases the frequency of large events to values much greater than for systems without diffusion.
    • Building Safe Families Through Educating on Adverse Childhood Experiences

      Dabney, Katie E.; Dahl, Heather; McMorrow, Samantha; Henze-Nelson, Brenda (2018-05)
      There is a strong correlation between families that work with child welfare agencies and the prevalence of maltreatment during childhood. Adverse childhood experiences (ACEs) have been linked to poor health outcomes but are much more negatively correlated when 3 or more ACEs have been experienced during a childhood (Hunt, Slack & Berger, 2017; Crouch, Strompolis, Bennett, Morse, & Radcliff, 2017). Teaching parents about the impacts of ACEs and how they may more safely parent, can reduce the recidivism of future maltreatment in at-risk families who work with child welfare agencies. Education can give parents the power and motivation to make better decisions for themselves and for their families.
    • Bullying in middle school: the role of school counselors and teachers in preventing bullying

      Palmer, Paula Nicole; Topkok, Sean; Barnhardt, Ray; Roehl, Roy (2017-05)
      Research suggests that bullying is a problem in schools throughout the nation. Children spend the vast majority of their life attending school. School counselors and teachers are in a unique position to identify, prevent and educate students about bullying. The purpose of this project was to examine the role of school counselors and teachers in the Fairbanks North Star Borough School District (FNSBSD) in preventing bullying in their schools. The participants of this study were 8 school counselors and teachers from four middle schools in the FNSBSD. Data for this research was collected using an anonymous online survey utilizing www.SurveyMonkey.com. The results of the survey indicated that bullying is an issue in the four middle schools selected for the study in FNSBSD. Of the four major types of bullying discussed in my research (cyber, relation, physical, and verbal), there was a consensus among the participants that cyber and relational bullying were the most prevalent and problematic in their schools. Recommendations for future research include expanding on this study to include a larger sample of schools and participants, suggestions for strengthening staff training and implementing school based youth courts in FNSBSD schools as part of the bully intervention and prevention program.
    • Buoyancy Effects On Building Pressurization In Extreme Cold Climates

      Bargar, Harold Edward; Das, Debendra K.; Goering, Douglas J.; Johnson, Ronald A.; Lin, Chuen-Sen; Quang, Pham X. (2003)
      This research investigates building pressurization due to buoyancy effect. The American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) presents an idealized equation to calculate the buoyancy effect. This dissertation compares differential pressure measurements from an actual building exposed to extremely cold temperatures to this idealized model. It also presents new statistical models based on the collected data. These new models should provide engineers with improved tools to properly account for building pressurization for designs in extreme cold climates. Building pressurization, the differential pressure between the interior of a building and its exterior surroundings, is an important design consideration. Pressurization is the driving force in building infiltration/exfiltration. It also affects air flow within building zones. Improper calculation of pressurization can result in under-sizing the building's heating and cooling systems, improper operation of air distribution systems, improper operation of elevators, and freezing and failure of water distribution and circulation systems. Building pressurization is affected by: wind (speed and direction), exterior-to-interior temperature difference, and mechanical equipment operation. In extreme cold climates, the predominant effect is air buoyancy due to temperature differences across the building envelope. The larger the temperature difference, the larger the buoyancy effect. In extreme cold climates, the largest temperature differences often occur at times when wind speed is negligible. This dissertation also demonstrates the use of existing data sources such as building automation systems to collect data for basic research. Modern systems automation provides a tremendous amount of data that, in the past, had to be collected through separate instrumentation and data acquisition systems. Taking advantage of existing automation systems can provide the required data at greatly reduced costs when compared to previous industry practices. The statistical analysis approach taken in this research expands the tools for engineering design. Actual interactions of real world variables are analyzed and used to produce prediction models. These techniques allow the model to incorporate relationships which may not be fully understood at the underlying principle level but are evidenced in the data collected from actual installations.* *This dissertation includes a CD that is compound (contains both a paper copy and CD as part of the dissertation). The CD requires the following applications: Internet Browser; Adobe Acrobat; Microsoft Office; Image Viewer.
    • Calcareous fen vegetation and ecology and the disjunct Betula glandulosa in Southeastern Alaska

      Johnson, Joni M. (2006-08)
      Calcareous fens are rare within southeastern Alaska due to their unique geochemical setting, as are the plant communities produced by these environs. On a global scale these wetland types have been identified as valuable for their biodiversity and have received special protection. The first objective of this research was to characterize the floristics and hydrogeochemistry of a subset of calcareous fens on Chichagof Island in the northern Alexander Archipelago through intensive sampling within each site. Multivariate analyses were used to describe these wetland systems. The second objective of this study included investigating whether or not the disjunct Betula glandulosa (dwarf birch) population was restricted to its current site. B. glandulosa is a habitat generalist in its known range; however, it is found in only one location within the Alexander Archipelago. Germination and seedling transplant experiments were conducted that tested for the effects of site, competition, and the interaction between site and competition. In this manner a subset of calcareous fens in the region was described and abiotic parameters associated with B. glandulosa evaluated. Obtaining baseline information and understanding mechanisms behind these sources of regional biodiversity are important for monitoring purposes and detecting disturbance effects
    • Calibration of an on-line analyzer using neural network modeling

      Yu, Shaohai (2003-08)
      The goal of the project was to predict the ash content of raw coal in real time using the Americium-137 and Cesium-241 scintillation counts from an on-line analyzer. Rather than regression methods (that are current industrial practice), neural networks were used to map the scintillation counts to percentage ash. Quick stop training was used to prevent overfitting The noise and sparseness of the data required that the training, calibration and prediction subsets are statistically similar to each other. Therefore, Kohonen networks were first used to detect the features present in the data set. Three subsets were then built such that they had representative members from each feature. Neural network models were developed for the screened coal, the unscreened coal and the combined data respectively. The results show that the performance of the combined model was comparable to the performance with two different models for the screened and unscreened data. Due to the variance in the sample data, the neural networks (screened, unscreened and combined) did not predict individual samples well. The network predictions were, however, accurate on the average. Compared to the common regression approach, neural network modeling demonstrated much better performance in ash prediction based on certain criteria.
    • Calibration of microbolometer infrared cameras for measuring volcanic ash mass loading

      Carroll, Russell C.; Hawkins, Joseph; Thorsen, Denise; Raskovic, Dejan; Hatfield, Michael (2014-08)
      Small spacecraft with thermal infrared (TIR) imaging capabilities are needed to detect dangerous levels of volcanic ash that can severely damage jet aircraft engines and must be avoided. Grounding aircraft after a volcanic eruption may cost the airlines millions of dollars per day, while accurate knowledge of volcanic ash density might allow for safely routing aircraft around dangerous levels of volcanic ash. There are currently limited numbers of satellites with TIR imaging capabilities so the elapsed time between revisits can be large, and these instruments can only resolve total mass loading along the line-of-sight. Multiple small satellites could allow for decreased revisit times as well as multiple viewing angles to reveal the three-dimensional structure of the ash cloud through stereoscopic techniques. This paper presents the design and laboratory evaluation of a TIR imaging system that is designed to fit within the resource constraints of a multi-unit CubeSat to detect volcanic ash mass loading. The laboratory prototype of this TIR imaging system uses a commercial off-theshelf (COTS) camera with an uncooled microbolometer sensor, two narrowband filters, a black body source and a custom filter wheel. The infrared imaging system detects the difference in attenuation of volcanic ash at 11 μm and 12 μm by measuring the brightness temperature at each band. The brightness temperature difference method is used to measure the column mass loading. Multi-aspect images and stereoscopic techniques are needed to estimate the mass density from the mass loading, which is the measured mass per unit area. Laboratory measurements are used to characterize the noise level and thermal stability of the sensor. A calibration technique is developed to compensate for sensor temperature drift. The detection threshold of volcanic ash density of this TIR imaging system is found to be from 0.35 mg/m3 to 26 mg/m3 for ash clouds that have thickness of 1 km, while ash cloud densities greater than 2.0 mg/m3 are considered dangerous to aircraft. This analysis demonstrates that a TIR imaging system for determining whether the volcanic ash density is dangerous for aircraft is feasible for multi-unit Cubesat platforms.
    • Calving ground habitat selection: Teshekpuk Lake and Western Arctic caribou herds

      Kelleyhouse, Rebecca A. (2001-12)
      Barren-ground caribou (Rangifer tarandus granti) exhibit relative fidelity to calving grounds each spring. The Western Arctic Herd (WAH) and Teshekpuk Lake Herd (TLH) calve separately on Alaska's north slope, each selective of the dominant vegetation type. The WAH consumed mostly sedges, though the TLH diet varied. Despite differing snow conditions between the calving grounds, both herds were selective of the lowest snow cover class. Rugged terrain was avoided by both herds. While the TLH selected a high rate of increase in biomass, the WAH selected high biomass at calving and at peak lactation. Climate trends (1985-2001) were variable. There was a warming trend on the WAH calving ground, though no significant trends were present on the TLH calving ground, as expressed by median NDVI on 21 June. These herds have similar winter ranges and population trends, yet they differ in respect to habitat composition, selection and climate patterns during calving.
    • Can I tell you what really happened?: learning to make decisions in response to indigenous student voice in a high school language arts classroom

      Rushman, Alyssa M.; Patterson, Leslie; Siekmann, Sabine; Martelle, Wendy (2019-05)
      This study focuses on engaging high school students in reading and the decisions I make to sustain that engagement. I learned that one way to enhance the engagement in my classroom is to listen to my students' stories and to incorporate culturally relevant texts. All of the students in this study were previously in our school's language intervention program: Read 180. While teaching this intervention-based class, I noticed this class was a behavior management nightmare. The students' challenging behavior led me to question the intervention program's ability to sustain my students' engagement through the prescribed texts. This study aims to describe my observations in a 10th grade Language Arts II class in Chefornak, Alaska. Specifically, this thesis describes my findings and analysis as it relates to how students show engagement and how I make (and revise) decisions in response to my students' voices. I used teacher action research (TAR) to research the events in my classroom. During an 11-week period, I collected audio recordings, student work samples, and teacher action research journal entries. At the end of the research, I also wrote memos about the data. I used constructive grounded theory (CGT) to make sense of the story the data tells and to see what kind of patterns were present. This research is important to me because it helps me to understand the weaknesses and the strengths in my own instructional planning as well as how I interpret students' participation in class. After this research, I am convinced that learning outcomes are preceded by learner engagement, and that learner engagement is complex.
    • Can tax policy change exploration levels? A case of Alaska oil legislation.

      Tappen, Samuel Weston; Baek, Jungho; Little, Joseph; Reynolds, Douglas (2014-08)
      This thesis applies modern Autoregressive Distributed Lag modeling techniques to estimate the effects of oil tax policy in the case of the 2007 ACES legislation on exploratory drilling within Alaska. This analysis uses recently released public data to examine the period of 1986 to 2013 in quarterly intervals which includes all periods in which ACES was in place. While this subject has become a popular subject of debate within the state and industry, no similar statistical analysis has been conducted to date. According to the results, ACES had a significantly negative and lasting effect on exploration levels while it was in effect. The oil price and interest rate are also found to be important variables in characterizing exploration activity.
    • Can We Remain Yup'ik In These Contemporary Times? A Conversation Of Three Yugtun-Speaking Mothers

      Michael, Veronica E.; Marlow, P. (2010)
      The Yup'ik people of southwestern Alaska are experiencing language shift from Yugtun to English. This study is a conversation between three Yugtun speaking mothers who are trying to understand this shift and wondering if they can maintain their identity, and that of their children, in this changing world. The study takes place in the village of Kuiggluk. Data collection included a research journal and focus group discussions. In this study, I have tried to paint a picture of who we are as Yup'ik mothers in our contemporary lives. Qayaruaq, Mikngayaq and I carry with us our own mothers' teachings, while at the same time we face different situations in school and schooling. Through our discussions we sought to understand the reasons for language loss/shift -- a shift that seems to be driving us away from our culture.
    • Canenermiut lifeways and worldview and western fish and wildlife management

      Jack, Carl T. (2002-12)
      The Canenermiut inter-generational worldview embodies the proper use and conservation of the resources necessary to sustain life from time immemorial. The classical Yupiaq conservation ethics in the utilization of subsistence resources are well established and practiced to this day by Canenermiut that is geared to the survival of their culture and community. When western fish and wildlife managers promulgate regulations from urban areas of Alaska on the taking of subsistence resources in rural Alaska they often find out that rural residents such as the Canenermiut ... are unwilling to follow the regulations. Caneneq is a coastal area between Kusquqvak (Kuskokwim) Bay up to Qaluyaaq (Nelson Island). Canenermiut is made up of two Yupiaq words, Caneneq as defined earlier and the suffix miut is a Yup'ik word defined as occupant of that geographic area or a place. The people from these villages see the imposition of the western precepts of fish and wildlife management systems as efforts by outsiders to control their way of life. They see this effort as inconsistent with their worldview of how a human should fit within the creation of a higher being. These people do not participate in the formulation of public policies or the promulgation of the regulations that affect their lives and as a consequence do not have a sense of ownership of them. The Canenermiut worldviews are fundamentally different from the worldview of the people of European origin who brought with them concepts of lifeways foreign to Alaska's indigenous people. The author of this thesis is one of Canenermiut from the Native Village of Kipnuk, who was raised by his parents the traditional Yupiaq way of life and taught by his uncle the art of hunting and fishing. He is also one who was also educated in schools of the dominant western society. As one of many other Alaska Native children who were subjected to the assimilation effort of the United States government in the image of the Other, the author is very cognizant of both the Other's lifeways and the classical Yupiaq lifeways ... The author having lived in both worlds, the world of Canenermiut in the Native Village of Kipnuk and in Anchorage will attempt to articulate the major components of Canenermiut worldview. This is a worldview that western fish and wildlife managers do not understand but ones that may help in enhancing the conservation and utilization of these subsistence resources. Secondly, the author will attempt to articulate the degree of the paradigm shift in the Canenermiut indigenous value system that has occurred among this generation. The desire of the Canenermiut to retain their cultural value system and to control their destiny is affirmed by the author. In addition, as the precepts of fish and wildlife management systems are accepted over time by Alaska Native people outside of the geographic area of Caneneq, the Canenermiut do not want to be left behind and have a strong desire to- participate in these management systems.
    • Capacitance measurements of bulk salinity and brine movement in first-year sea ice

      Backstrom, Lars G. E. (2007-05)
      Sea ice is an important component of the global climate system, as it changes the properties of the ocean-atmosphere interface. Understanding sea ice requires detailed knowledge of its temperature and bulk salinity. To measure these attributes using non-destructive in-situ techniques, instruments were frozen into first-year sea ice, and analysed jointly with ice-core, mass balance and climate data. The bulk salinity of the ice is calculated from measurements of temperature and complex dielectric permittivity at 50 MHz in landfast ice in McMurdo Sound, Antarctica, the Chukchi Sea, Alaska, and in an outdoor tank experiment in Fairbanks, Alaska. A simple relation for estimating brine volume fraction and bulk salinity in columnar, bubble-free ice from the real part of the complex dielectric permittivity was derived. For relative brine volumes below 50-70 % the error in the derived bulk salinity was below 15%. The observed brine movement events are analyzed. The data clearly indicate the extent and impact of brine movement on ice temperature and salinity. The analysis of a drainage event recorded by both the temperature and dielectric permittivity probe provided insight into gravity drainage of brine driven by a large brine reservoir in the freeboard layer.
    • CARBON AND NITROGEN ASSIMILATION IN THE CLAMS NUCULANA RADIATA AND MACOMA MOESTA FROM THE BERING SEA

      Weems, Jared; Iken, Katrin; Gradinger, Rolf; Wooller, Matthew (University of Alaska Fairbanks, 2011-08)
      The predicted climate-induced reduction in sea ice presence in the Bering Sea could impact benthic trophic interactions; however, species-specific consumer dependence on ice algal production is largely unknown. My objective was to track feeding in the benthic clams, Nuculana radiata and Macoma moesta, using stable carbon and nitrogen isotopes. Nuculana radiata had slow isotopic assimilation rates, with lipids taking up isotope markers fastest and muscle tissue the slowest. Lipids may thus be particularly suitable to track the immediate ingestion of sea ice algal export in benthic consumers. When isotopically enriched food was added to natural sediment cores, N. radiata assimilated 60% less of the isotope markers than when feeding on algal food in isolation. Possibly, this difference is related to the ingestion of other, naturally present food sources in the sediment. Macoma moesta showed 30% higher isotopic assimilation compared to N. radiata in sediment cores. I suggest that differing feeding behaviors between the species provide differential access to the sedimented algal food. Based on these results, N. radiata is likely better able to utilize food sources buried in the sediment and may be more competitive over M. moesta under conditions of reduced ice algal production in the northern Bering Sea.
    • Carbon And Nitrogen Flows In Zero -Water Exchange Shrimp Culture: Inferences Using Stable Isotope Tracers

      Epp, Michelle A.; Schell, Donald M. (2002)
      Nutrient and energy flow in cultures of Pacific White Shrimp, Litopenaeus vannamei, were examined in zero-water exchange, 1200--1300 L mesocosms at the Oceanic Institute (OI), Waimanalo, Hawaii. A technique was developed for monitoring shrimp use of formulated feeds through the addition of stable isotopically labeled nutrients to the feed ingredients. Crystalline amino acid compounds were ineffective as labels due to their rapid dissolution in the tank water with feed pellet break-up. Labels which were 'packaged' as algal cells prior to addition to the feed pellets were more effectively incorporated into shrimp tissues than crystalline label (approximately 27% versus 8% for crystalline label). The 'packaged' label technique was also used to test soluble proteins from pollock processing wastes (stickwater) as a feeding stimulant for Litopenaeus vannamei. Indoor controlled condition experiments and outdoor experiments with natural pond biota compared stickwater amended feed to squid liver powder amended feed for growth and assimilation by the shrimp. Initial results indicated that pollock processing by-products might function as a feeding stimulant in shrimp aquaculture. The addition of 15N-ammonium to outdoor shrimp tanks showed that natural tank production contributed significantly to shrimp growth requirements providing between 17 and 77% of the growth nitrogen. When labeled ammonium was added to black covered tanks, shrimp had slower growth rates (0.5 g/wk as compared to 0.7 g/wk for uncovered ammonium addition tanks) but significant uptake of this label, with a tank biota contributing 23%. This finding supported a bacterial role in shrimp nutrition that will require further study. Isotopic analysis of individual amino acids in shrimp muscle from outdoor tanks with and without added 15N-ammonium further established the role of tank natural populations to shrimp nutrition. Rapid increases in delta 15N for threonine one day after label addition suggested an increased requirement for this essential amino acid. Further identification of the contribution of tank biota to shrimp amino acid profiles will require profiles of the delta 15N of specific amino acids for suspended particulate organic matter.
    • Carbon And Nitrogen Isotope Ratios In Bowhead Whales (Balaena Mysticetus) And Their Zooplankton Prey As Indicators Of Feeding Strategy And Environmental Change.

      Vinette, Kimberly Ann; Schell, Don (1993)
      This study details regional, seasonal and inter-annual differences in $\delta\sp{13}$C and $\delta\sp{15}$N of zooplankton in the Bering and Chukchi Seas. These isotopic variations were correlated with inter-annual and long-term variations in $\delta\sp{13}$C and $\delta\sp{15}$N of bowhead whale baleen.<p> Statistical analyses indicate significant $\sp{13}$C-enrichment in Bering/Chukchi seas zooplankton relative to Beaufort Sea zooplankton, supporting the observed trends of $\sp{13}$C-depletion at higher latitudes and enrichment at lower latitudes. Bering/Chukchi seas zooplankton show a weak trend in $\sp{13}$C-depletion between 1987-1990, possibly due to inter-annual environmental changes affecting phytoplankton $\delta\sp{13}$C. The $\delta\sp{13}$C of baleen produced in fall/winter months is inversely correlated to sea surface temperature trends in the Bering Sea. Long-term changes in baleen $\delta\sp{13}$C may be helpful in assessing past climatic change.<p> The observed $\delta\sp{15}$N oscillations in baleen may be due to changes in trophic level of prey between seasonal feeding grounds or from physiological cycles in the bowhead whale. <p>
    • Carbon and nitrogen uptake dynamics during 1997 and 1998 anomalous conditions in the Bering Sea

      Rho, TaeKeun (2000-12)
      During 1997 and 1998, unusual physical conditions caused dramatic changes in the regional oceanic environment and function of the southeastern Bering Sea ecosystem. The changes in ecosystem function were examined using ¹³C and ¹⁵N tracer techniques. In 1997, unusually clear and calm conditions allowed an ice-related early bloom over the middle shelf of the southeastern Bering Sea and resulted in nitrate uptake below the pycnocline. In 1998, the duration of phytoplankton growth was extended by warm temperatures and frequent storms that resulted in slow growth of phytoplankton and prevented rapid utilization of nitrate over the shelf. In coccolithophorid bloom regions, ammonium concentrations were high (>3 uM), while nitrate concentrations had a larger range (O.1-10.8 uM). Nitrate utilization rates, which estimate 'new' production, were similar for both years and were somewhate greater (ca. 30%) than those observed during the 70's and 80's PROBES studies. The fate of primary production may have differed in 1997 and 1998.