Now showing items 2502-2521 of 3321

• #### Satellite thermal remote sensing of the volcanoes of Alaska and Kamchatka during 1994-1996, and the 1994 eruption of Kliuchevskoi volcano

The Advanced Very High Resolution Radiometers on the NOAA polar orbiting satellites were used to routinely observe the volcanoes of Alaska and Kamchatka from May 1994 to July 1996, as part of the monitoring effort of the Alaska Volcano Observatory. The largest eruption observed during this period occurred at Kliuchevskoi Volcano between September 8 and October 2, 1994. Radiative temperature measurements made during this eruption were used to develop quantitative methods for analyzing volcanic thermal anomalies. Several parameters, including maximum temperature, anomalous pixels, and total volcanic signal (TVS), were compared to viewing angle and date. A new quantity, TVS7, may most effectively monitor the temporal evolution of the eruption using thermal data. By combining several observations of the thermal state of the volcano, the general nature of the volcanic activity can be described. These observations may indicate an elevation in temperature twelve to 24 hours before an ash-producing event.
• #### Satellite to model comparisons of volcanic ash emissions in the North Pacific

To detect, analyze and predict the movement of volcanic ash in real time, dispersion models and satellite remote sensing data are important. A combination of both approaches is discussed here to enhance the techniques currently used to quantify volcanic ash emissions, based on case studies of the eruptions of the Kasatochi (Alaska, USA, 2008), Mount Redoubt (Alaska, USA, 2009) and Sarychev Peak (Russia, 2009) volcanoes. Results suggest a quantitative approach determining masses from satellite images can be problematic due to uncertainties in knowledge of input values, most importantly the ground surface temperature required in the mass retrieval. Furthermore, a volcanic ash transport and dispersion model simulation requires its own set of accurate input parameters to forecast an ash cloud's future location. Such input parameters are often difficult to assess, especially in real time volcano monitoring, and default values are often used for simplification. The objective of this dissertation is to find a quantitative comparison technique to apply to satellite and volcanic ash transport and dispersion models that reduces the inherent uncertainty in the results. The binary 'Ash -- No Ash' approach focusing on spatial extent rather than absolute masses is suggested, where the ash extent in satellite data is quantitatively compared to that in the dispersion model's domain. In this technique, neither satellite data nor dispersion model results are regarded as the truth. The Critical Success Index (CSI) as well as Model and Satellite Excess values (ME and SE, respectively) are introduced as comparison tools. This approach reduces uncertainties in the analysis of airborne volcanic ash and, due to the reduced list of input parameters and assumptions in satellite and model data, the results will be improved. This decreased complexity of the analysis, combined with a reduced error as the defined edge of ash cloud is compared in each method rather than defined threshold or mass loading, will have important implications for real time monitoring of volcanic ash emissions. It allows for simpler, more easily implemented operational monitoring of volcanic ash movements.
• #### Saxitoxins: role of prokaryotes

Saxitoxins, the toxins associated with paralytic shellfish poisoning (PSP), are synthesized by dinoflagellates, cyanobacteria, and possibly bacteria. The specific objectives of this study were to determine growth conditions that promote high and low levels of toxin accumulation in Aphanizomenon flos-aquae (cyanobacterium) and Pseudomonas stutzeri (bacterium). Putative saxitoxins of P. stutzeri identified by HPLC-FLD in this study, and previously by other laboratories, were determined to be 'imposters' based on their chemical and physical properties, suggesting that this bacterium may not synthesize PSP toxins. In the cyanobacterium, toxin production was enhanced under higher light intensities and temperatures. Toxin accumulation reached maximal levels when cellular nitrogen was from either (NO₃-+NH₄)-N or N₂-N, while urea-N drastically reduced toxin levels. These data will be used in future studies aimed at identifying the genes involved in saxitoxin synthesis via molecular technologies that rely upon expression of the 'saxitoxin genes' under different growth conditions.
• #### Scaling laws in cold heavy oil production with sand reservoirs

This thesis presents a rigorous step by step procedure for deriving the minimum set of scaling laws for Cold Heavy Oil Production with Sand (CHOPS) reservoirs based on a given set of physical equations using inspectional analysis. The resulting dimensionless equations are then simulated in COMSOL Mutiphysics to validate the dimensionless groups and determine which groups are more significant by performing a sensitivity analysis using a factorial design. The work starts simple by demonstrating how the above process is done for 1D single-phase flow and then slowly ramps up the complexity to account for foamy oil and then finally for wormholes by using a sand failure criterion. The end result is three dimensionless partial differential equations to be solved simultaneously using a finite element simulator. The significance of these groups is that they can be used to extrapolate between a small scale model and a large scale prototype.
• #### School Connectedness: the benefits of a school-based peer-mentoring program for transitioning students in secondary education

The transition to a new high school can disrupt social networks, cause anxiety, and hinder academic success for secondary students. School-based comprehensive peer-mentoring programs that focus on transitioning secondary students have the potential to alleviate the anxiety of a changing school climate by promoting school connectedness, building peer relationships, and being sensitive to the social, academic, and procedural concerns of transitioning secondary students (Cauley & Jovanovich, 2006). Students who feel connected to school feel personally accepted, respected, included, and supported by others in the school social environment, all of which may guard against student alienation, poor self-esteem, and other deviant behaviors for adolescent youth. The following research paper discusses how focused school-based peer-mentoring programs for adolescents may help to build school and peer connectedness; promote academic achievement, healthy development, and psychological health; increase protective factors; and decrease risky behaviors. A presentation and program guide for secondary administration and staff were developed based on the information found in the literature review.
• #### School counselors: preparing transitioning high school students

Without preparedness for possible career avenues after graduation, many youth struggle with career paths they may want to investigate. even the considerably prepared students are uncertain what they are going to do after high school. having transition classes starting in middle school can further enhance students' career paths once they graduate from high school. this project focuses on rural school counselors helping to prepare high school students transition into possible career opportunities. rural school counselors often have additional advocate duties to help keep a positive connectedness between students and their schools. increased connectedness and transition classes can make the transition process much more manageable for students after they graduate from high school (Grimes, Haskins, & Paisley, 2013).
• #### A school-based group counseling cirriculum for adolescent girls experiencing low self-esteem

This project reviews the existing literature on adolescent development in females, and demonstrates the importance of school counselors facilitating small group counseling with students who experience low self-esteem. Although research suggests social-emotional development begins in childhood, and the American School Counselor Association requires a social-emotional component to school counseling programs, there are few resources available to secondary school counselors who see a need for an effective group counseling curriculum for females with low self-esteem. This project aims to provide secondary school counselors with such a curriculum.
• #### A school-based intervention program for preadolescent girls experiencing body dissatisfaction

Body dissatisfaction and poor body image are issues girls are facing in their preadolescent years. Research is demonstrating that preadolescent girls need intervention programs to help support them with the struggles of body image and self-acceptance. This project uses the literature and established research to provide school counselors with a program to help meet the needs of preadolescent girls struggling with body dissatisfaction and promote body acceptance and body positivity.
• #### Schools in rural Alaska with higher rates of student achievement: a search for positive deviance in education

This study sought to identify schools in rural Alaska with higher rates of student achievement and study what factors contribute to that success. Alaska Native students make up a large majority of the students attending school in small remote villages across the state. Data, however, have shown that Alaska Native students constantly perform lower than any other demographic group on every subject level and lower at every grade level when tested using state assessments. This study begins with a journey to understand the complexity of the problems that affect schooling in rural Alaska, ranging from teacher turnover to school district size and oversight. However, it is important to examine this current challenge by examining the history of education and how that history has affected Alaska Native people today. To identify schools in rural Alaska with higher rates of student achievement, a binary variable was used to determine positive deviance. Data analysis drew on academic achievement of each school as measured by the 5-year average score of the school in three subjects: Reading, Mathematics and Writing. While the results did not yield a case study for positive deviance, the findings and conclusion, using a critical race theory lens question whether schools today, intentionally or unintentionally, are still modeled after the same framework and operate in the same fashion as they did when they were intended to assimilate Alaska Natives to become better citizens. Using an advocacy worldview, this study draws upon the unchallenged truth that schools in rural Alaska may never perform as a collective as well as or better than their urban counterparts under this model.
• #### Science Education In Rural America: Adaptations For The Ivory Tower

This thesis illustrated what can happen when academic culture disconnects from the cultures surrounding it. It showed that formal school environments are not always the best places to learn. A discussion of the debate between coherence and fragmentation learning theories illustrated academic chasms and a mindset that science education must originate from within ivory towers to be valued. Rationales for place-based science education were developed. Two National Science Foundation initiatives were compared and contrasted for relevance to Native Science education (a) Informal Science Education and (b) Science Education for New Civic Engagement and Responsibilities. A National Science Foundation instrument, known as the Self-Assessment of Learning Gains, was selected to field-test measures of learning science outside of university science courses. Principles of chemistry were taught in community workshops, and those participant self-assessments were compared to self-assessments of students in introductory chemistry courses at two universities. University students consistently claimed the greatest learning gains, in the post-course survey, for the same areas that they claimed to have the greatest understanding, in the pre-course survey. The workshop participant responses differed, depending upon location of the learning environment. When held in a university laboratory, ideas were not related to other cultures, even when a Native Elder was present to describe those relationships. When held in a cultural center, those relationships were among the highest learning gains claimed. One of the instrument's greatest assets was the ability to measure reactions, level 4 of Bennett's (1976) hierarchy of evidence for program evaluation. A long-term commitment to informal science education (not short-term exhibits or programs), combined with negotiated place-based education was recommended as a crucially needed initiative, if relationships between universities and Native American communities are to improve. Some chasms created within ivory towers may never be bridged. Yet, those ideological chasms do not have to exist everywhere. The realities of working in the natural world and the practice of addressing multitudes of community challenges can alter perspectives, when horizons change from the edge of one's desk to those that meet the sea or sky.
• #### Science education in rural America: adaptations for the Ivory Tower

This thesis illustrated what can happen when academic culture disconnects from the cultures surrounding it. It showed that formal school environments are not always the best places to learn. A discussion of the debate between coherence and fragmentation learning theories illustrated academic chasms and a mindset that science education must originate from within ivory towers to be valued. Rationales for place-based science education were developed. Two National Science Foundation initiatives were compared and contrasted for relevance to Native Science education (a) Informal Science Education and (b) Science Education for New Civic Engagement and Responsibilities. A National Science Foundation instrument, known as the Self-Assessment of Learning Gains, was selected to field-test measures of learning science outside of university science courses. Principles of chemistry were taught in community workshops, and those participant self-assessments were compared to self-assessments of students in introductory chemistry courses at two universities. University students consistently claimed the greatest learning gains, in the post-course survey, for the same areas that they claimed to have the greatest understanding, in the pre-course survey. The workshop participant responses differed, depending upon location of the learning environment. When held in a university laboratory, ideas were not related to other cultures, even when a Native Elder was present to describe those relationships. When held in a cultural center, those relationships were among the highest learning gains claimed. One of the instrument's greatest assets was the ability to measure reactions, level 4 of Bennett's (1976) hierarchy of evidence for program evaluation. A long-term commitment to informal science education (not short-term exhibits or programs), combined with negotiated place-based education was recommended as a crucially needed initiative, if relationships between universities and Native American communities are to improve. Some chasms created within ivory towers may never be bridged. Yet, those ideological chasms do not have to exist everywhere. The realities of working in the natural world and the practice of addressing multitudes of community challenges can alter perspectives, when horizons change from the edge of one's desk to those that meet the sea or sky.
• #### Science for Alaska: place for curious learners

For over 25 years, Alaskans have been attending Science for Alaska Lecture Series, held during the coldest part of an Alaskan winter. The hour-long evening lectures would see from around 100 to almost 300 people attend each event. The scientific literature is quiet in regard to audience preferences in regard to the recieving end of science communication. This qualitative study looked at the audience of a science lecture series: who are they, why do they come and what do they do with the information. In nine taped audio interviews, the research participants described themselves as smart, curious lifelong learners who felt a sense of place to the Arctic for its practical and esoteric values. Attending the events constructed their social identity that they felt important to share with children. The findings suggest that addressing the audience's sense of place and mirroring their view as smart, curious people would be an effective avenue to communicate science.
• #### Scintillation at K-band and Ka-band frequencies

The need for higher bandwidth and smaller antenna size for satellite communications led NASA to fund the Advanced Communications Technology Satellite (ACTS) and propagation research for K-band and Ka-band frequencies. From December 1993 to December 1998, seven sites in North America have collected and processed power measurements at 20.2 and 27.5 gigahertz from ACTS, a geostationary statellite located at 100 ̊West longitude. The thesis compares scintillation measurements to eight scintillation prediction models, proposes a cumulative distribution model to help predict the percentage of time scintillation exceeds a given threshold, examines the effects of frequency on scintillation magnitudes, and proposes a climate model based on moisture content to help predict scintillation magnitudes. The study concludes that the scintillation prediction models are dependent on the climate, the frequency dependence is a function of climate, and the moisture content in the atmosphere dictates the percentage of time large scintillation occurs.
• #### Screw configuration effects during twin-screw extrusion of starchy and proteinaceous materials

This study investigated the effects of screw configuration and feed composition during extrusion of starchy and proteinaceous materials. All experiments were carried out in a twin-screw extruder with a length/diameter ratio of 32:1. The screw speed, feed flow rate, and moisture content were 400 rpm, 12 kg/h, and 15%, respectively. Kneading block (KB) and reverse screw elements (RSE) were placed at different locations in the 200 mm experimental zone near the die, where the temperature was maintained at $\rm 150\sp\circ C.$ An on-line method for measurement of residence time distribution (RTD) in a food extruder was developed, tested, and validated. The technique was based on the electrical conductivity of the material in the die, which was altered by addition of an electrolyte tracer at the feed inlet. The change in current flow was measured as a proportional voltage response across a resistor. The on-line method correlated well with the established erythrosine dye method and precisely determined the effects of screw speed, feed flow rate, screw configuration on RTD. The effects of type, length and position of mixing elements and spacing between two elements on energy inputs, RTD, molecular changes of starch, and macroscopic extrudate characteristics were compared. The results showed that the specific mechanical energy (SME), mean residence time, and extent of starch breakdown were higher for screw profiles with RSE than that with KB. These parameters also increased with longer mixing elements, increased distance of the elements from the die, and with increased spacing between two elements. Specific thermal energy (STE) input showed opposite trend to that of SME. Die temperature was highest when the elements were placed at 0 mm from the die. Such a screw profile produced an extrudate with highest overall expansion and lowest apparent density. Radial expansion was highest with KB in the screw profile than with RSE. KB seemed to be the element of choice for maximizing radial expansion. Increasing mixing element length or spacing between two elements decreased product expansion. Hardness of the product decreased linearly with increasing radial expansion as shown by the breaking strength data. Changing feed composition by adding Arrowtooth flounder muscle decreased the SME input, increased STE and mean residence time. Hydrolysis changed the properties of Arrowtooth flounder muscle so much that it enhanced the expansion characteristics of starch in rice flour and improved extrudate texture.
• #### Sea change, know fish: catching the tales of fish and men in Cordova, Alaska

Cordova, Alaska is a coastal community in Southcentral Alaska with an intricate history in commercial fishing, primarily for the Copper River sockeye salmon industry, which extends historically to pre-statehood. This dissertation collects personal narratives as a method to express cultural features of community identity and the role salmon has played in shaping identity, livelihood, and lifestyle in Cordova, Alaska. Research material is based on oral history interviews from which I construct written character portraits to depict aspects of resident life in this fishing community and from others who use the community to access summer salmon resources of the Copper River. Portraits were performed and presented in public venues to obtain casual feedback from and review by community members from Cordova and other participants in the Prince William Sound drift fishery. The portraits and public commentary post-performance or from community readers serve as one basis for analysis and lead to my conclusions about life in this community and, on a larger scale, cultural dimensions common within other communities (either geographic or occupational). Public performances offer a communication tool that provides a method to share differences within the industry without encountering explicit controversy over challenging industry transitions. Although the tool of storytelling does not typically receive significant media or policy attention, I find it very effective in understanding and mediating conflict across different groups of people, especially when the main theme of conflict, sustainability and access to the fishery resource, is a mutual cultural feature of interest to diverse participant groups. Additionally, public creative performances offer a venue of communication primarily designed for entertainment and as a result, the audience interaction with storytellers occurs more casually and perhaps more genuinely than it does in academic conferences or policy meeting venues. Personal stories related to the iconic feature of salmon with mutual significance in state and federal fisheries of the North Pacific are a valuable, intimate source of local and traditional knowledge. The opportunity to put meaningful and commonly shared emphasis on the fish as an economic and cultural resource and not on a particular stakeholder group may help lead to improved communications in a field that tends to illicit conflict in consideration of access to harvest rights.
• #### Sea ice near-inertial response to atmospheric storms

A moored oceanographic array was deployed on the Beaufort Sea continental slope from August 2008-August 2009 to measure Arctic sea ice near-inertial motion in response to rapidly changing wind stress. Upward looking Acoustic Doppler Current Profilers detected sea ice and measured ice drift using a combination of bottom track and error velocity. An analysis of in-situ mooring data in conjunction with data from National Center for Environmental Prediction (NCEP) reanalysis suggest that many high and low pressure systems cross the Beaufort in winter, but not all of these create a near-inertial ice response. Two unusually strong low pressure systems that passed near the array in December 2008 and February/March 2009 were accompanied by elevated levels of near-inertial kinetic energy in the ice. The analysis suggests pressure systems which have a diameter to ground track velocity ratio close to 3/4 of the local inertial period can excite a large near-inertial response in the sea ice. It is conjectured that this results from the combined effect of resonance arising from similar intrinsic timescales of the storm and the local inertial period and from stresses that are able to overcome the damping of sea ice arising from ice-mechanics and damping in the ice-ocean boundary layer. Those systems whose intrinsic times scales do not approach resonance with the local inertial period did not excite a large near- inertial response in the sea ice. From an analysis of two storms in February 2009, and two in December 2008, it appears that wind stresses associated with previous low pressure systems preconditioned the ice pack, allowing for larger near-inertial response during subsequent events.
• #### Sea-ice habitat preference of the Pacific walrus (Odobenus rosmarus divergens) in the Bering Sea: a multiscaled approach

The goal of this thesis is to define specific parameters of mesoscale sea-ice seascapes for which walruses show preference during important periods of their natural history. This research thesis incorporates sea-ice geophysics, marine-mammal ecology, remote sensing, computer vision techniques, and traditional ecological knowledge of indigenous subsistence hunters in order to quantitatively study walrus preference of sea ice during the spring migration in the Bering Sea. Using an approach that applies seascape ecology, or landscape ecology to the marine environment, our goal is to define specific parameters of ice-patch descriptors and mesoscale seascapes in order to evaluate and describe potential walrus preference for such ice and the ecological services it provides during an important period of their life-cycle. The importance of specific sea-ice properties to walrus occupation motivates an investigation into how walruses use sea ice at multiple spatial scales when previous research suggests that walruses do not show preference for particular floes. Analysis of aerial imagery, using image processing techniques and digital geomorphometric measurements (floe size, shape, and arrangement), demonstrated that while a particular floe may not be preferred, at larger scales a collection of floes, specifically an ice-patch (< 4 km²), was preferred. This shows that walruses occupy ice patches with distinct ice features such as floe convexity, spatial density, and young ice and open water concentration. Ice patches that are occupied by adult and juvenile walruses show a small number of characteristics that vary from those ice patches that were visually unoccupied. Using synthetic aperture radar imagery, we analyzed co-located walrus observations and statistical texture analysis of radar imagery to quantify seascape preferences of walruses during the spring migration. At a coarse resolution of 100-9,000 km², seascape analysis shows that, for the years 2006-2008, walruses were preferentially occupying fragmented pack ice seascapes range 50-89% of the time, when, all throughout the Bering Sea, only range 41-46% of seascapes consisted of fragmented pack ice. Traditional knowledge of a walrus' use of sea ice is investigated through semi-directed interviews conducted with subsistence hunters and elders from Savoonga and Gambell, two Alaskan Native communities on St. Lawrence Island, Alaska. Informants were provided with a large nautical map of the land and ocean surrounding St. Lawrence Island and 45 printed largeformat aerial photographs of walruses on sea ice to stimulate discussion as questions were asked to direct the topics of conversation. Informants discussed change in sea ice conditions over time, walrus behaviors during the fall and spring subsistence hunts, and sea-ice characteristics that walruses typically occupy. These observations are compared with ice-patch preferences analyzed from aerial imagery. Floe size was found to agree with remotely-sensed ice-patch analysis results, while floe shape was not distinguishable to informants during the hunt. Ice-patch arrangement descriptors concentration and density generally agreed with ice-patch analysis results. Results include possible preference of ice-patch descriptors at the ice-patch scale and fragmented pack ice preference at the seascape scale. Traditional knowledge suggests large ice ridges are preferential sea-ice features at the ice-patch scale, which are rapidly becoming less common during the fall and spring migration of sea ice through the Bering Sea. Future work includes increased sophistication of the synthetic aperture radar classification algorithm, experimentation with various spatial scales to determine the optimal scale for walrus' life-cycle events, and incorporation of further traditional knowledge to investigate and interface crosscultural sea-ice observations, knowledge and science to determine sea ice importance to marine mammals in a changing Arctic.
• #### Seabird Habitat Use And Zooplankton Abundance And Biomass In Relation To Water Mass Properties In The Northern Gulf Of Alaska

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

This study investigated the macroscale distribution of seabirds in relation to oceanography in a neritic environment characterized by well-defined water masses (the northern Bering Sea) and an oceanic environment characterized by weaker differences between water masses (the northern North Pacific Ocean). In the northern Bering Sea, the total density (birds/km$\sp2)$ of all seabirds combined and densities and/or frequencies of occurrence of seven of nine species of seabirds that exhibited significant differences among water masses showed the strongest attraction to Anadyr Water. In general, attractions were second highest in Bering Shelf Water, third highest in Two-layered Water (Alaska Coastal Water overlying Bering Shelf Water), and lowest in Alaska Coastal Water. This pattern of seabird distributions reflected distributions of zooplankton biomass, which were highest in Anadyr Water and consisted of species that were large enough to be eaten directly by seabirds. Further, whereas copepods in Bering Shelf Water also are large, they are much smaller in Alaska Coastal Water and, thus, must pass through more trophic levels to fishes before the energy is directly accessible to seabirds. Consequently, zooplankton-based food webs dominated in Anadyr and Bering Shelf waters and fish-based food webs dominated in Two-layered and Alaska Coastal waters. In addition, seabirds concentrated near a strong, mesoscale thermal front between Bering Shelf and Alaska Coastal waters. In the northern North Pacific, assemblages of seabirds exhibited three main groupings, a "subarctic assemblage," a "transitional assemblage," and a "'subtropical/tropical assemblage." These assemblages matched those for zooplankton, squids, and fishes in the same vicinity, suggesting that there are geographically- and temporally-stable biological communities in the North Pacific that are associated with well-defined, persistent physical environments. The total density of all seabirds combined and densities and/or frequencies of occurrence of 13 of 16 species of seabirds that exhibited significant two-way ANOVAs exhibited primarily a water mass effect; only one species exhibited primarily a year effect, and two exhibited primarily an interaction (i.e., a change in habitat use between years).