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• 13111. [Article] Population characteristics and movement patterns of redband trout (Oncorhynchus mykiss) and mountain whitefish (Prosopium williamsoni) in the Crooked River, Oregon

  Over the last decade, the Oregon Department of Fish and Wildlife (ODFW) has documented a precipitous decline in the Crooked River redband trout (Oncorhynchus mykiss) population, prompting this study to ...

  Citation × Citation Citation Abstract Copy Title: Population characteristics and movement patterns of redband trout (Oncorhynchus mykiss) and mountain whitefish (Prosopium williamsoni) in the Crooked River, Oregon Author: Nesbit, Shivonne M. Over the last decade, the Oregon Department of Fish and Wildlife (ODFW) has documented a precipitous decline in the Crooked River redband trout (Oncorhynchus mykiss) population, prompting this study to address potential factors contributing to the decline. There are two main goals to this project: (1) identify potential factors contributing to the reduction of the redband trout population in the Crooked River fishery and (2) provide management recommendations to all of the agencies responsible for managing the Crooked River that might effect a change in the redband trout population trend. This thesis had three objectives: (1) evaluate the movement patterns of redband trout and mountain whitefish in the Crooked River below Bowman Dam, (2) monitor total dissolved gas levels (TDG) in the Crooked River to evaluate the incidence of supersaturated water and gas bubble disease in redband trout and mountain whitefish and (3) implement a more comprehensive population estimate survey to document both redband trout and mountain whitefish population densities. Prior to this study, limited data existed on the distribution and movement patterns of redband trout and mountain whitefish in the Crooked River below Bowman Dam. Based on the results from the 2-year telemetry study, redband trout and mountain whitefish population exhibit a resident life history strategy and stay in the Wild and Scenic Section of the Crooked River below Bowman Dam. Two potential explanations for the observed population decline were plausible: the decline was actually a decline, or the fish moved to other sections of the Crooked River downstream of Bowman Dam. The telemetery study showed that redband trout and mountain whitefish stay within this section of river, thereby providing evidence against the explanation that the observed population decline was a result of movement of fish to other sections of river. The total dissolved gas study demonstrated that gas saturation levels become elevated enough to cause gas bubble disease in the Crooked River below Bowman Dam. The gas saturation in the Crooked River is equivalent or higher than levels shown to produce gas bubble disease (GBD) in fishes. When flows exceed 600 cfs, the total dissolved gas saturation exceeds the maximum Oregon Department of Environmental Quality mandated level of 110% gas saturation in the Crooked River. Flows in excess of 600cfs are common during spring runoff events below Bowman Dam. From 1989-2009, flows exceeded 600 cfs in 13 of the 21 years and 1000 cfs in 10 of the 21 years. The past population effects of high flows and supersaturated waters on redband trout and mountain whitefish are difficult to quantify, but based on the hydrograph and the saturation curve, the years when gas bubble disease might have been present in fish can be predicted. Given the strong linear relationship between TDG and stream average daily discharge (r2 = 0.93), discharge itself can be used as a predictive tool for assessing TDG levels in the river. Based on the flow data from the USBOR gauging station and the gas saturation curve for the wild and scenic section of the Crooked River generated here, gas bubble disease was probably present in fish in 1993, 1996, 1997, 1998, 1999, and 2004. The redband trout population density has varied considerably from year to year, with a peak observed in 1994 and the lowest point observed in 2006. A large increase in the number of redband trout per km occurred between 1993 and 1994, indicating that the density of fish can increase substantially in one year. The decline in redband trout density from 1994 to 2006 appears to be more gradual than the increase in density observed from 1993 to 1994. Since 2006, the redband trout population density appears to be increasing based on qualitative patterns. One interesting finding was that in 2007, the mountain whitefish density was estimated to be 7 times greater than the redband trout population, in 2008 it was estimated to be 4 times greater, but in 2009, the mountain whitefish density was only marginally higher than the redband trout population. In the three years of this study, there appears to be a shift in the relative abundance of redband trout and mountain whitefish directly below Bowman Dam. The reduction in the mountain whitefish population density from 2007 to 2008 was not expected based on angler accounts of the increase in mountain whitefish population densities. Title: Population characteristics and movement patterns of redband trout (Oncorhynchus mykiss) and mountain whitefish (Prosopium williamsoni) in the Crooked River, Oregon Author: Nesbit, Shivonne M. Over the last decade, the Oregon Department of Fish and Wildlife (ODFW) has documented a precipitous decline in the Crooked River redband trout (Oncorhynchus mykiss) population, prompting this study to address potential factors contributing to the decline. There are two main goals to this project: (1) identify potential factors contributing to the reduction of the redband trout population in the Crooked River fishery and (2) provide management recommendations to all of the agencies responsible for managing the Crooked River that might effect a change in the redband trout population trend. This thesis had three objectives: (1) evaluate the movement patterns of redband trout and mountain whitefish in the Crooked River below Bowman Dam, (2) monitor total dissolved gas levels (TDG) in the Crooked River to evaluate the incidence of supersaturated water and gas bubble disease in redband trout and mountain whitefish and (3) implement a more comprehensive population estimate survey to document both redband trout and mountain whitefish population densities. Prior to this study, limited data existed on the distribution and movement patterns of redband trout and mountain whitefish in the Crooked River below Bowman Dam. Based on the results from the 2-year telemetry study, redband trout and mountain whitefish population exhibit a resident life history strategy and stay in the Wild and Scenic Section of the Crooked River below Bowman Dam. Two potential explanations for the observed population decline were plausible: the decline was actually a decline, or the fish moved to other sections of the Crooked River downstream of Bowman Dam. The telemetery study showed that redband trout and mountain whitefish stay within this section of river, thereby providing evidence against the explanation that the observed population decline was a result of movement of fish to other sections of river. The total dissolved gas study demonstrated that gas saturation levels become elevated enough to cause gas bubble disease in the Crooked River below Bowman Dam. The gas saturation in the Crooked River is equivalent or higher than levels shown to produce gas bubble disease (GBD) in fishes. When flows exceed 600 cfs, the total dissolved gas saturation exceeds the maximum Oregon Department of Environmental Quality mandated level of 110% gas saturation in the Crooked River. Flows in excess of 600cfs are common during spring runoff events below Bowman Dam. From 1989-2009, flows exceeded 600 cfs in 13 of the 21 years and 1000 cfs in 10 of the 21 years. The past population effects of high flows and supersaturated waters on redband trout and mountain whitefish are difficult to quantify, but based on the hydrograph and the saturation curve, the years when gas bubble disease might have been present in fish can be predicted. Given the strong linear relationship between TDG and stream average daily discharge (r2 = 0.93), discharge itself can be used as a predictive tool for assessing TDG levels in the river. Based on the flow data from the USBOR gauging station and the gas saturation curve for the wild and scenic section of the Crooked River generated here, gas bubble disease was probably present in fish in 1993, 1996, 1997, 1998, 1999, and 2004. The redband trout population density has varied considerably from year to year, with a peak observed in 1994 and the lowest point observed in 2006. A large increase in the number of redband trout per km occurred between 1993 and 1994, indicating that the density of fish can increase substantially in one year. The decline in redband trout density from 1994 to 2006 appears to be more gradual than the increase in density observed from 1993 to 1994. Since 2006, the redband trout population density appears to be increasing based on qualitative patterns. One interesting finding was that in 2007, the mountain whitefish density was estimated to be 7 times greater than the redband trout population, in 2008 it was estimated to be 4 times greater, but in 2009, the mountain whitefish density was only marginally higher than the redband trout population. In the three years of this study, there appears to be a shift in the relative abundance of redband trout and mountain whitefish directly below Bowman Dam. The reduction in the mountain whitefish population density from 2007 to 2008 was not expected based on angler accounts of the increase in mountain whitefish population densities. Close

• 13112. [Article] Some aspects of the comparative ecology of fishes associated with juvenile sockeye salmon, Oncorhynchus nerka (Walbaum), in the lakes of the Naknek river system, Alaska

  A study of the distribution, relative abundance and diet of fishes sympatric with juvenile sockeye salmon, Oncorhynchus nerka (Walbaum), within the freshwater nursery areas of the Naknek River system was ...

  Citation × Citation Citation Abstract Copy Title: Some aspects of the comparative ecology of fishes associated with juvenile sockeye salmon, Oncorhynchus nerka (Walbaum), in the lakes of the Naknek river system, Alaska Author: Wallace, Richard L. A study of the distribution, relative abundance and diet of fishes sympatric with juvenile sockeye salmon, Oncorhynchus nerka (Walbaum), within the freshwater nursery areas of the Naknek River system was undertaken from 1961 to 1963. The study was part of an extensive investigation to determine what factors in the freshwater environment were limiting the size of the populations of sockeye salmon returning to the rivers of Bristol Bay, Alaska. The speties found associated with juvenile salmon in the limnetic zones of the Naknek system were the pond smelt, Hypomesus olidus (Pallas); the least cisco, Coregonus sardinella Valenciennes; the threespine stickleback, Gasterosteus aculeatus Linnaeus; and the ninespine stickleback, Pungitius pungitius (Linnaeus). Life history information was collected for these sympatric species. Tow nets were used to capture samples of fish from the limnetic portions of the nursery areas. Some samples were collected by beach seines, lake traps and otter trawls. Plankton samples were collected and compared to the diets of the limnetic fishes. Although some confusion has existed in the literature, I concluded that pond smelt of the Naknek system belong to Hypomesus olidus (Pallas). The populations of smelt were comprised of six age-groups in the late summer, but most specimens belonged to three age-groups. Most members of the species spawn in the spring of the fourth year of life. The estimated fecundity ranged from 900 to 4,300 eggs per female. Seven age-groups of least ciscoes were present in the populations of the Naknek system. The species in the Naknek system probably spawned for the first time in the fall of their fourth year. The estimated fecundity of two specimens was 4,006 and 14,380 eggs. Populations of three spine stickleback were comprised of three age-groups of fish. I was unable to assign ages to ninespine stickleback. Estimates of the fecundity of the species ranged from 116 to 456 eggs per female. All species studied were distributed throughout the Naknek system. The relative abundance of the fishes studied was variable between and within nursery areas and from year to year. The population densities of pond smelt and threespine stickleback were larger in the surface waters compared to the deep waters. The relative abundance of sockeye fry, yearlings and ninespine stickleback was greater in the surface stratum rather than the deep stratum in most nursery areas. The five main food items utilized by these limnetic species were cladocerans (Bosmina sp. and Daphnia sp.); copepods (cyclopoid copepods and Diaptomus sp.); and Dipteran insects. Analysis of the similarity of diets indicated that the diets of sockeye fry and pond smelt were more similar than were the diets of sockeye fry or yearlings and any other sympatric species. The diet of sockeye fry was more similar to that of either species of stickleback than was the diet of sockeye yearlings. An analysis of the food of various sizes of each species of fish indicated the diets of three age-groups of smelt were more similar than the diets of various age-groups of any other fish. The food composition of three age-groups of ciscoes and two size groups of both species of stickleback showed a strong positive correlation. The diets of sockeye fry and yearlings showed the weakest positive correlation of the species studied. All species of fish studied selectively fed on one or more components of the zooplankton. Daphnia sp. and cyclopoid copepods were strongly selected in Lake Coville. Cyclopoids were selected in South Bay. Bosmina sp. was selected from the waters of West End. In Lake Coville, the greatest potential competition for food probably existed between the large populations of pond smelt and sockeye fry. In the West End nursery area, potential competition between juvenile salmon and both species of stickleback may not be severe, depending on the age composition of the salmon population present in the nursery area. The possibility exists that the relatively low numbers of adult sockeye salmon returning to the comparatively rich lakes of the Naknek River system is due to the presence of large populations of sympatric species of fish. Each of these sympatric species feed on the same general types of food organisms as do the juvenile salmon and may affect the numbers of young salmon that leave the lake, and subsequently return from the ocean. Title: Some aspects of the comparative ecology of fishes associated with juvenile sockeye salmon, Oncorhynchus nerka (Walbaum), in the lakes of the Naknek river system, Alaska Author: Wallace, Richard L. A study of the distribution, relative abundance and diet of fishes sympatric with juvenile sockeye salmon, Oncorhynchus nerka (Walbaum), within the freshwater nursery areas of the Naknek River system was undertaken from 1961 to 1963. The study was part of an extensive investigation to determine what factors in the freshwater environment were limiting the size of the populations of sockeye salmon returning to the rivers of Bristol Bay, Alaska. The speties found associated with juvenile salmon in the limnetic zones of the Naknek system were the pond smelt, Hypomesus olidus (Pallas); the least cisco, Coregonus sardinella Valenciennes; the threespine stickleback, Gasterosteus aculeatus Linnaeus; and the ninespine stickleback, Pungitius pungitius (Linnaeus). Life history information was collected for these sympatric species. Tow nets were used to capture samples of fish from the limnetic portions of the nursery areas. Some samples were collected by beach seines, lake traps and otter trawls. Plankton samples were collected and compared to the diets of the limnetic fishes. Although some confusion has existed in the literature, I concluded that pond smelt of the Naknek system belong to Hypomesus olidus (Pallas). The populations of smelt were comprised of six age-groups in the late summer, but most specimens belonged to three age-groups. Most members of the species spawn in the spring of the fourth year of life. The estimated fecundity ranged from 900 to 4,300 eggs per female. Seven age-groups of least ciscoes were present in the populations of the Naknek system. The species in the Naknek system probably spawned for the first time in the fall of their fourth year. The estimated fecundity of two specimens was 4,006 and 14,380 eggs. Populations of three spine stickleback were comprised of three age-groups of fish. I was unable to assign ages to ninespine stickleback. Estimates of the fecundity of the species ranged from 116 to 456 eggs per female. All species studied were distributed throughout the Naknek system. The relative abundance of the fishes studied was variable between and within nursery areas and from year to year. The population densities of pond smelt and threespine stickleback were larger in the surface waters compared to the deep waters. The relative abundance of sockeye fry, yearlings and ninespine stickleback was greater in the surface stratum rather than the deep stratum in most nursery areas. The five main food items utilized by these limnetic species were cladocerans (Bosmina sp. and Daphnia sp.); copepods (cyclopoid copepods and Diaptomus sp.); and Dipteran insects. Analysis of the similarity of diets indicated that the diets of sockeye fry and pond smelt were more similar than were the diets of sockeye fry or yearlings and any other sympatric species. The diet of sockeye fry was more similar to that of either species of stickleback than was the diet of sockeye yearlings. An analysis of the food of various sizes of each species of fish indicated the diets of three age-groups of smelt were more similar than the diets of various age-groups of any other fish. The food composition of three age-groups of ciscoes and two size groups of both species of stickleback showed a strong positive correlation. The diets of sockeye fry and yearlings showed the weakest positive correlation of the species studied. All species of fish studied selectively fed on one or more components of the zooplankton. Daphnia sp. and cyclopoid copepods were strongly selected in Lake Coville. Cyclopoids were selected in South Bay. Bosmina sp. was selected from the waters of West End. In Lake Coville, the greatest potential competition for food probably existed between the large populations of pond smelt and sockeye fry. In the West End nursery area, potential competition between juvenile salmon and both species of stickleback may not be severe, depending on the age composition of the salmon population present in the nursery area. The possibility exists that the relatively low numbers of adult sockeye salmon returning to the comparatively rich lakes of the Naknek River system is due to the presence of large populations of sympatric species of fish. Each of these sympatric species feed on the same general types of food organisms as do the juvenile salmon and may affect the numbers of young salmon that leave the lake, and subsequently return from the ocean. Close

• 13113. [Article] Health Insurance Exchanges

  Examining committee: Colleen Chrisinger

  Citation × Citation Citation Abstract Copy Title: Health Insurance Exchanges Author: Fracchia, Elena, Hall, Tiffany, Remer, Matthew, Saxe, Karen, Wu, Wei-Ting Year: 2011 Examining committee: Colleen Chrisinger Title: Health Insurance Exchanges Author: Fracchia, Elena, Hall, Tiffany, Remer, Matthew, Saxe, Karen, Wu, Wei-Ting Year: 2011 Examining committee: Colleen Chrisinger Close

• 13114. [Article] The biology and pathogenicity of a sheath nematode Hemicycliophora similis Thorne, 1955

  A study, using greenhouse and laboratory experiments, was made of Hemicycliophora similis from Bandon, Oregon to determine: identity and morphometrics, time and development of a life cycle, host plant ...

  Citation × Citation Citation Abstract Copy Title: The biology and pathogenicity of a sheath nematode Hemicycliophora similis Thorne, 1955 Author: McKewan, Jeanette Anne A study, using greenhouse and laboratory experiments, was made of Hemicycliophora similis from Bandon, Oregon to determine: identity and morphometrics, time and development of a life cycle, host plant preferences and optimum environmental conditions for reproduction and pathogenicity. Morphometric investigations revealed discrepancies between the measurements of this nematode species and those recorded in nematological literature for H. similis. Personal communications with R. P. Esser, H. J. Jensen and B. M. Zuckerman suggested the variations noted do not necessitate describing a new species. For purposes of this research the nematode is named Hemicycliophora sirnilis. Life history investigations were conducted to determine the number of days required to complete a life cycle and the various stages as the nematode developed from egg to egg. Eggs mature to first-stage larvae, without sheath or spear, in 3-5 days and hatch as second-stage larvae in 8-10 days. Second-stage larvae inoculated onto carrot seedlings matured into third-stage larvae in 12-15 days. Fourth-stage larvae appeared in 25-28 days, and adults were present in 35-38 days. Embryonating eggs were observed lodged within an incompletely shed fourth-stage cuticle attached to adult females and within the normal sheath surrounding the adult. One molting specimen was found with two eggs lodged within the fourth-stage cuticle. Such eggs were seen to develop to second-stage larvae; however, none were observed over a long enough time period to determine if larvae hatched and emerged free of the cuticular confinement. Evaluated as hosts were beet, broccoli, carrot, corn, dill, pea, radish, rutabaga, tomato and turnip. Carrot, tomato and turnip supported the highest increase in population; no substantial increase was observed on beet, broccoli, corn and dill. The nematode formed galls consisting of large multibranched growths and reproduced on many of the plant species tested. Galling of seedling roots was most severe on carrot, but slight galling was observed on beet, rutabaga and turnip. Multibranching was observed with varying severity in all hosts. Germination of carrot seeds was reduced substantially when grown in sandy soil infested with H. similis. Slight germination reductions occurred with all hosts tested except corn and pea. Adults and larvae were observed feeding behind root tips and on nematode induced galls. Root discoloration was noted on several plants. To evaluate temperature and soil optima, rooted cranberry cuttings, germinated cranberry seedlings and carrot seedlings were utilized. Carrot seeds were planted in sandy soils of two different textures and pH, infested with H. similis and grown in three temperature regimes: 30°C and 24°C night, 22°C day and 14°C night and 30°C day 6 °C night. The optimum temperature for reproduction on carrot was 22°C day 14°C night in both soil types. A pH gradient developed in cups with the least acidic pH occurring at the base corresponding to maximum nutrient uptake by plant roots. The soil mix in which bog sand from Bandon was incorporated developed a more acidic condition presumably due to the additional organic N content which supplied ammonical nitrogen. The soil mix with Newport sand had no additional organic N and a less acidic condition developed. Maximum nematode population and root density also occurred at the base of the cup. Plants grown in infested soil had sparse multibranched roots; no galls were observed in this experiment. Cranberry cuttings were grown in sterile bog soil from Bandon, Oregon and inoculated with 225 nematodes/450 cc soil. The optimum temperature for nematode reproduction and plant growth was 30°C and 24°C night. Runner growth and root dry weights were not significantly effected by nematode feeding. Germinated cranberry seedlings were subjected to similar conditions; temperature response was similar to that of cuttings. Root dry weights and runner growth of cranberry seedlings was greater in nematode inoculated treatments than non-inoculated controls: nematode feeding on cranberry roots resulted in an increase of multibranching. This research indicated nematode feeding was detrimental to growth of a variety of plant species. High soil populations of H. similis caused severe reductions to root growth and seed germination. However, since this study was conducted in controlled conditions, it was not substantiated that this nematode caused a reduction of growth to field-grown cranberry plants. Further investigations are needed to correlate these findings with field data to determine pathogenicity on cranberry. Title: The biology and pathogenicity of a sheath nematode Hemicycliophora similis Thorne, 1955 Author: McKewan, Jeanette Anne A study, using greenhouse and laboratory experiments, was made of Hemicycliophora similis from Bandon, Oregon to determine: identity and morphometrics, time and development of a life cycle, host plant preferences and optimum environmental conditions for reproduction and pathogenicity. Morphometric investigations revealed discrepancies between the measurements of this nematode species and those recorded in nematological literature for H. similis. Personal communications with R. P. Esser, H. J. Jensen and B. M. Zuckerman suggested the variations noted do not necessitate describing a new species. For purposes of this research the nematode is named Hemicycliophora sirnilis. Life history investigations were conducted to determine the number of days required to complete a life cycle and the various stages as the nematode developed from egg to egg. Eggs mature to first-stage larvae, without sheath or spear, in 3-5 days and hatch as second-stage larvae in 8-10 days. Second-stage larvae inoculated onto carrot seedlings matured into third-stage larvae in 12-15 days. Fourth-stage larvae appeared in 25-28 days, and adults were present in 35-38 days. Embryonating eggs were observed lodged within an incompletely shed fourth-stage cuticle attached to adult females and within the normal sheath surrounding the adult. One molting specimen was found with two eggs lodged within the fourth-stage cuticle. Such eggs were seen to develop to second-stage larvae; however, none were observed over a long enough time period to determine if larvae hatched and emerged free of the cuticular confinement. Evaluated as hosts were beet, broccoli, carrot, corn, dill, pea, radish, rutabaga, tomato and turnip. Carrot, tomato and turnip supported the highest increase in population; no substantial increase was observed on beet, broccoli, corn and dill. The nematode formed galls consisting of large multibranched growths and reproduced on many of the plant species tested. Galling of seedling roots was most severe on carrot, but slight galling was observed on beet, rutabaga and turnip. Multibranching was observed with varying severity in all hosts. Germination of carrot seeds was reduced substantially when grown in sandy soil infested with H. similis. Slight germination reductions occurred with all hosts tested except corn and pea. Adults and larvae were observed feeding behind root tips and on nematode induced galls. Root discoloration was noted on several plants. To evaluate temperature and soil optima, rooted cranberry cuttings, germinated cranberry seedlings and carrot seedlings were utilized. Carrot seeds were planted in sandy soils of two different textures and pH, infested with H. similis and grown in three temperature regimes: 30°C and 24°C night, 22°C day and 14°C night and 30°C day 6 °C night. The optimum temperature for reproduction on carrot was 22°C day 14°C night in both soil types. A pH gradient developed in cups with the least acidic pH occurring at the base corresponding to maximum nutrient uptake by plant roots. The soil mix in which bog sand from Bandon was incorporated developed a more acidic condition presumably due to the additional organic N content which supplied ammonical nitrogen. The soil mix with Newport sand had no additional organic N and a less acidic condition developed. Maximum nematode population and root density also occurred at the base of the cup. Plants grown in infested soil had sparse multibranched roots; no galls were observed in this experiment. Cranberry cuttings were grown in sterile bog soil from Bandon, Oregon and inoculated with 225 nematodes/450 cc soil. The optimum temperature for nematode reproduction and plant growth was 30°C and 24°C night. Runner growth and root dry weights were not significantly effected by nematode feeding. Germinated cranberry seedlings were subjected to similar conditions; temperature response was similar to that of cuttings. Root dry weights and runner growth of cranberry seedlings was greater in nematode inoculated treatments than non-inoculated controls: nematode feeding on cranberry roots resulted in an increase of multibranching. This research indicated nematode feeding was detrimental to growth of a variety of plant species. High soil populations of H. similis caused severe reductions to root growth and seed germination. However, since this study was conducted in controlled conditions, it was not substantiated that this nematode caused a reduction of growth to field-grown cranberry plants. Further investigations are needed to correlate these findings with field data to determine pathogenicity on cranberry. Close

• 13115. [Article] Responsive pedagogies of practice : researching an ambitious secondary mathematics teacher education design

  Design in secondary mathematics teacher education must prepare teacher candidates to do the work of ambitious and equitable mathematics teaching with skill by situating development in the work of teaching ...

  Citation × Citation Citation Abstract Copy Title: Responsive pedagogies of practice : researching an ambitious secondary mathematics teacher education design Author: Campbell, Matthew Paul, 1983- Design in secondary mathematics teacher education must prepare teacher candidates to do the work of ambitious and equitable mathematics teaching with skill by situating development in the work of teaching and incorporating opportunities to investigate and enact teaching. Teacher education designs must also be responsive to the work that mathematics teachers are expected to do in school settings--which are a product of a set of goals, expectations, and communities that have formed over long histories. This dissertation pursues novel and emerging questions around what the design and implementation of a responsive and practice-focused approach to teacher education--what I call a responsive pedagogy of practice--entails, how those entailments are informed by the work of teaching in schools, and how those entailments inform what individuals do in teacher education programs. Three manuscripts collectively illustrate progress on these ideas, drawing upon data and analyses from design-based research in a secondary mathematics teacher education program. The first manuscript addresses a question of what is meant by and entailed in the design and implementation of a responsive pedagogy of practice. Through an intertwined process of design, implementation, analyses, and revision, three sets of findings informing the development of a theory of responsive pedagogies of practice emerged. First, two needs emerged in addition to the initial attention to developing teacher candidates' instructional skill--aligning with the mathematics of the secondary classroom and developing teacher candidates’ mathematical knowledge for teaching (MKT; Ball, Thames, & Phelps, 2008). The negotiation of these multiple needs poses a challenge for teacher educators. This negotiation also gave rise to a second finding involving the development of instructional skill, which needs to focus on the development on multiple levels of pedagogical tools. Further, a set of pedagogical tools must be derived, in part, from the work that teacher candidates do in school settings. Ultimately, this means that responsiveness in teacher education entails preparing teacher candidates to do what is typically done in school settings while also finding the openings at which to press for more ambitious and equitable teaching practice. Finally, a third finding emerged regarding the novel roles for teacher educators and partner teachers that are constructed through a responsive and practice-focused pedagogy of teacher education. The second manuscript highlights analyses conducted to further investigate the features of the activity of secondary mathematics teaching to which a teacher education design needs to be responsive. Data from teacher candidates' enactments across two settings--the university methods courses and their student teaching placements--were drawn upon to identify the entailments of the activity of secondary mathematics teaching. A modified analytic framework from Leont’ev (1981) and Wertsch, Minick, and Arns (1984) was used to analyze the work of teacher candidates in each setting. While the work in the methods courses emphasized providing students access to mathematics and the orchestration of goal-directed discussions, work in student teaching placements was defined by efficient and productive work on mathematical procedures. Opportunities for more novel instruction were made available contingent on the two expectations being met. These findings have implications for what pedagogical tools should be developed through a responsive pedagogy of practice that enable efficient and procedurally focused mathematics work while also making progress on increasingly ambitious and equitable instruction. The third manuscript highlights an example of how an emerging sense of responsive and practice-focused approaches to teacher education and the work of teacher candidates in school classrooms inform the design features of a responsive pedagogy of practice. A specific design example is put forth that situates opportunities of enactment in the work of addressing students' mathematics errors in the midst of work with students on mathematics procedures. As such, the example is derived from the work that teacher candidates do in school classrooms and also shows how a design can attend to the multiple needs related to teacher candidate and student development. The example serves as one of many activities in development--all of which are subject to further examination through a design-based research process. Title: Responsive pedagogies of practice : researching an ambitious secondary mathematics teacher education design Author: Campbell, Matthew Paul, 1983- Design in secondary mathematics teacher education must prepare teacher candidates to do the work of ambitious and equitable mathematics teaching with skill by situating development in the work of teaching and incorporating opportunities to investigate and enact teaching. Teacher education designs must also be responsive to the work that mathematics teachers are expected to do in school settings--which are a product of a set of goals, expectations, and communities that have formed over long histories. This dissertation pursues novel and emerging questions around what the design and implementation of a responsive and practice-focused approach to teacher education--what I call a responsive pedagogy of practice--entails, how those entailments are informed by the work of teaching in schools, and how those entailments inform what individuals do in teacher education programs. Three manuscripts collectively illustrate progress on these ideas, drawing upon data and analyses from design-based research in a secondary mathematics teacher education program. The first manuscript addresses a question of what is meant by and entailed in the design and implementation of a responsive pedagogy of practice. Through an intertwined process of design, implementation, analyses, and revision, three sets of findings informing the development of a theory of responsive pedagogies of practice emerged. First, two needs emerged in addition to the initial attention to developing teacher candidates' instructional skill--aligning with the mathematics of the secondary classroom and developing teacher candidates’ mathematical knowledge for teaching (MKT; Ball, Thames, & Phelps, 2008). The negotiation of these multiple needs poses a challenge for teacher educators. This negotiation also gave rise to a second finding involving the development of instructional skill, which needs to focus on the development on multiple levels of pedagogical tools. Further, a set of pedagogical tools must be derived, in part, from the work that teacher candidates do in school settings. Ultimately, this means that responsiveness in teacher education entails preparing teacher candidates to do what is typically done in school settings while also finding the openings at which to press for more ambitious and equitable teaching practice. Finally, a third finding emerged regarding the novel roles for teacher educators and partner teachers that are constructed through a responsive and practice-focused pedagogy of teacher education. The second manuscript highlights analyses conducted to further investigate the features of the activity of secondary mathematics teaching to which a teacher education design needs to be responsive. Data from teacher candidates' enactments across two settings--the university methods courses and their student teaching placements--were drawn upon to identify the entailments of the activity of secondary mathematics teaching. A modified analytic framework from Leont’ev (1981) and Wertsch, Minick, and Arns (1984) was used to analyze the work of teacher candidates in each setting. While the work in the methods courses emphasized providing students access to mathematics and the orchestration of goal-directed discussions, work in student teaching placements was defined by efficient and productive work on mathematical procedures. Opportunities for more novel instruction were made available contingent on the two expectations being met. These findings have implications for what pedagogical tools should be developed through a responsive pedagogy of practice that enable efficient and procedurally focused mathematics work while also making progress on increasingly ambitious and equitable instruction. The third manuscript highlights an example of how an emerging sense of responsive and practice-focused approaches to teacher education and the work of teacher candidates in school classrooms inform the design features of a responsive pedagogy of practice. A specific design example is put forth that situates opportunities of enactment in the work of addressing students' mathematics errors in the midst of work with students on mathematics procedures. As such, the example is derived from the work that teacher candidates do in school classrooms and also shows how a design can attend to the multiple needs related to teacher candidate and student development. The example serves as one of many activities in development--all of which are subject to further examination through a design-based research process. Close

• 13116. [Article] Application of transport-reaction modeling to constrain biogeochemical processes in marine sediments

  Quantifying the mass transport through marine sediments, and the geochemical response to such flow with numerical models has become a common and powerful approach for geochemical data interpretation. In ...

  Citation × Citation Citation Abstract Copy Title: Application of transport-reaction modeling to constrain biogeochemical processes in marine sediments Author: Hong, Wei-Li Quantifying the mass transport through marine sediments, and the geochemical response to such flow with numerical models has become a common and powerful approach for geochemical data interpretation. In this dissertation, I developed and applied transport-reaction models to unravel complex and interdependent reactions involving carbon, sulfur and silica transformations in shallow marine sediments, and the impact of physical (mass transport deposits) and depositional events (volcanic ash input) on the overall geochemical state of the system. Carbon cycling in the gas hydrate bearing sediments of the Ulleung Basin was quantified using both box and kinetic modeling approaches. The box model balances mass, flux, and carbon isotopes of carbon (Chapter 2), and led to a better understanding of how methane is cycled in the marine sediments of this area. This effort demonstrates the significance of CO₂ reduction, a previously overlooked reaction. The picture of reaction network derived from this work serves as the foundation for a transport-reaction model (Chapter 3). The kinetic model results revealed a very different biogeochemistry between two distinct fluid-flow environments. At sites where transport is predominantly diffusive (non-chimney environments), organic matter decomposition is the dominant process driving production of methane, dissolved inorganic carbon (DIC) and consumption of sulfate. In contrast, anaerobic oxidation of methane (AOM) drives both carbon and sulfur cycles in the advective settings characterized by acoustic chimneys indicative of gas transport. I show that methane produced within the model domain, through CO₂ reduction and methanogenesis, fuels AOM in the non-chimney sites while AOM is primarily induced by methane from external sources at the chimney sites. A simulation of the system evolution from a non-chimney to a chimney condition was developed by increasing the bottom methane supply to an originally diffusion-controlled site. Results from this exercise show that the higher methane flux leads to a higher AOM activity, and enhanced organic matter decomposition through methanogenesis. Organic carbon cycling is also affected by changes in the depositional environment, as shown by application of the kinetic model to the sediments from the Krishna-Godavary (K-G) basin along the eastern Indian margin (Chapter 4). Proximity to large rivers results in the widespread occurrence of mass transport deposits (MTD) throughout the basin. In this work, MTD is defined as a fluidized sediment block whose pore water composition is identical to sea water value to reflect the homogenization process during sediment transport. The pore water sulfate and ammonium profiles measured at seven sites drilled in the K-G Basin during the NGHP-01 expedition were simulated to provide a quantitative description of how MTDs can affect geochemistry profiles, not only for sulfate and ammonium but potentially all pore water species. This model provides reliable estimates of the MTDs thickness, the time elapsed after the most recent event, and the organoclastic sulfate reduction rate at these seven sites. A transport-reaction modeling approach was also applied to investigate the silica diagenetic reactions fueled by volcanic ash decomposition in Shikuko Basin, Nankai Trough (Chapter 5). The model developed for this setting reproduces a silica diagenetic boundary (SDB) at each site, which is defined by marked decreases in reactive volcanic ash, pore water silica and potassium. Volcanic ash alteration was constrained by modeling pore water ⁸⁷Sr/⁸⁶Sr profiles. Below the SDB, formation of clinoptilolite consumes potassium and regulates the extension of amorphous silica by consuming SiO₂(aq). The observed low SiO₂(aq) and dissolved potassium in these deep sequences require continuous precipitation of clinoptilolite; however in order to maintain oversaturation of this mineral at the low SiO₂(aq) in sediments below the SDB, an increase in pH is required, consistent with pore water observations. Thermal history, rather than temperature alone, controls the inferred reaction network as shown by the convergence of the thermal maturity of sediments at the SDB from all studied sites and is consistent with other locations documented onshore Japan. These results are valuable as we move forward in understanding the mechanisms and consequences of ash alteration in convergent margins worldwide. Title: Application of transport-reaction modeling to constrain biogeochemical processes in marine sediments Author: Hong, Wei-Li Quantifying the mass transport through marine sediments, and the geochemical response to such flow with numerical models has become a common and powerful approach for geochemical data interpretation. In this dissertation, I developed and applied transport-reaction models to unravel complex and interdependent reactions involving carbon, sulfur and silica transformations in shallow marine sediments, and the impact of physical (mass transport deposits) and depositional events (volcanic ash input) on the overall geochemical state of the system. Carbon cycling in the gas hydrate bearing sediments of the Ulleung Basin was quantified using both box and kinetic modeling approaches. The box model balances mass, flux, and carbon isotopes of carbon (Chapter 2), and led to a better understanding of how methane is cycled in the marine sediments of this area. This effort demonstrates the significance of CO₂ reduction, a previously overlooked reaction. The picture of reaction network derived from this work serves as the foundation for a transport-reaction model (Chapter 3). The kinetic model results revealed a very different biogeochemistry between two distinct fluid-flow environments. At sites where transport is predominantly diffusive (non-chimney environments), organic matter decomposition is the dominant process driving production of methane, dissolved inorganic carbon (DIC) and consumption of sulfate. In contrast, anaerobic oxidation of methane (AOM) drives both carbon and sulfur cycles in the advective settings characterized by acoustic chimneys indicative of gas transport. I show that methane produced within the model domain, through CO₂ reduction and methanogenesis, fuels AOM in the non-chimney sites while AOM is primarily induced by methane from external sources at the chimney sites. A simulation of the system evolution from a non-chimney to a chimney condition was developed by increasing the bottom methane supply to an originally diffusion-controlled site. Results from this exercise show that the higher methane flux leads to a higher AOM activity, and enhanced organic matter decomposition through methanogenesis. Organic carbon cycling is also affected by changes in the depositional environment, as shown by application of the kinetic model to the sediments from the Krishna-Godavary (K-G) basin along the eastern Indian margin (Chapter 4). Proximity to large rivers results in the widespread occurrence of mass transport deposits (MTD) throughout the basin. In this work, MTD is defined as a fluidized sediment block whose pore water composition is identical to sea water value to reflect the homogenization process during sediment transport. The pore water sulfate and ammonium profiles measured at seven sites drilled in the K-G Basin during the NGHP-01 expedition were simulated to provide a quantitative description of how MTDs can affect geochemistry profiles, not only for sulfate and ammonium but potentially all pore water species. This model provides reliable estimates of the MTDs thickness, the time elapsed after the most recent event, and the organoclastic sulfate reduction rate at these seven sites. A transport-reaction modeling approach was also applied to investigate the silica diagenetic reactions fueled by volcanic ash decomposition in Shikuko Basin, Nankai Trough (Chapter 5). The model developed for this setting reproduces a silica diagenetic boundary (SDB) at each site, which is defined by marked decreases in reactive volcanic ash, pore water silica and potassium. Volcanic ash alteration was constrained by modeling pore water ⁸⁷Sr/⁸⁶Sr profiles. Below the SDB, formation of clinoptilolite consumes potassium and regulates the extension of amorphous silica by consuming SiO₂(aq). The observed low SiO₂(aq) and dissolved potassium in these deep sequences require continuous precipitation of clinoptilolite; however in order to maintain oversaturation of this mineral at the low SiO₂(aq) in sediments below the SDB, an increase in pH is required, consistent with pore water observations. Thermal history, rather than temperature alone, controls the inferred reaction network as shown by the convergence of the thermal maturity of sediments at the SDB from all studied sites and is consistent with other locations documented onshore Japan. These results are valuable as we move forward in understanding the mechanisms and consequences of ash alteration in convergent margins worldwide. Close

• 13117. [Article] The impact of Oregon’s Coordinated Care Organizations on Prenatal Care Access and Quality : A Difference-in-Differences Analysis

  Background: Prenatal care (PNC) is an important preventive health service that can influence the health of the four million women who give birth annually in the United States, and the health their infants. ...

  Citation × Citation Citation Abstract Copy Title: The impact of Oregon’s Coordinated Care Organizations on Prenatal Care Access and Quality : A Difference-in-Differences Analysis Author: Muoto, Ifeoma O. Background: Prenatal care (PNC) is an important preventive health service that can influence the health of the four million women who give birth annually in the United States, and the health their infants. Despite efforts to increase women’s access to PNC services, significant disparities in PNC utilization and maternal/child health outcomes by insurance type and race/ethnicity persist in the United States. The past decade has witnessed several major health reforms at both national and state levels. However, the impact of these reforms on the quality of PNC, and on disparities in PNC utilization is not known. In 2012, the state of Oregon established Coordinated Care Organizations (CCOs) as comprehensive providers of care for Oregon’s Medicaid beneficiaries. CCOs are characterized by a global budget payment mechanism and financial incentives for high quality care. Timely initiation of PNC – which has been associated with improved maternal and infant health and utilization outcomes – is one of seventeen quality metrics for which CCOs can receive incentive payments. Objectives: The first objective of the current study was to estimate the impact of CCO implementation on the probability of initiating PNC in the first trimester, and on PNC adequacy among Oregon Medicaid beneficiaries. The second objective of the study was to determine if the implementation of CCOs influenced disparities in PNC utilization between Medicaid and privately-insured women, and between non-Hispanic White women and Hispanic/non-Hispanic Black women. Study Design: This quasi-experimental retrospective observational study drew from two data sources: Oregon Vital Records (Birth Certificate statistical files) from the department of Health Analytics of the Oregon state public health department and Washington State’s Linked Birth- CHARS (Comprehensive Hospital Abstract Reporting System) data from the Washington State department of health. A difference-in-differences approach examined PNC utilization before and after CCO implementation. Washington State served as the control group, as its Medicaid financing and delivery systems remained unchanged. Multivariable linear probability analysis was used to control for confounding factors, including maternal age, race/ethnicity, education, parity, marital status, smoking history, previous preterm birth, and maternal morbidity. Population Studied: All births in Oregon and Washington from 2008 – 2013, which were covered by either Medicaid or private insurance, were included in the analysis. Since CCOs started operating mid-year in 2012, June through December 2012 was considered a transition period and births during this period were excluded from the analysis. Principal Findings: CCO implementation was associated with a significant increase in the probability of PNC initiation in the first trimester and a reduction in insurance-type disparities in first trimester PNC initiation and PNC adequacy among Oregon Medicaid beneficiaries. Racial/ethnic disparities did not change following CCO implementation. Conclusions: The implementation of CCOs in Oregon had a positive impact on the timeliness of PNC initiation among Medicaid beneficiaries, and also reduced disparities in PNC quality between Medicaid and privately-insured women. Implications for Policy or Practice: The ongoing health system transformation in Oregon provides an ideal setting to assess the impact of a novel health service delivery model on PNC utilization. If Oregon is successful in this bold and unprecedented move, it could serve as a model for other Medicaid and commercial health plans seeking to improve PNC quality. Further study on the longer-term effects of CCO implementation on PNC quality as well as the effect of CCOs on other health care domains, is warranted. Title: The impact of Oregon’s Coordinated Care Organizations on Prenatal Care Access and Quality : A Difference-in-Differences Analysis Author: Muoto, Ifeoma O. Background: Prenatal care (PNC) is an important preventive health service that can influence the health of the four million women who give birth annually in the United States, and the health their infants. Despite efforts to increase women’s access to PNC services, significant disparities in PNC utilization and maternal/child health outcomes by insurance type and race/ethnicity persist in the United States. The past decade has witnessed several major health reforms at both national and state levels. However, the impact of these reforms on the quality of PNC, and on disparities in PNC utilization is not known. In 2012, the state of Oregon established Coordinated Care Organizations (CCOs) as comprehensive providers of care for Oregon’s Medicaid beneficiaries. CCOs are characterized by a global budget payment mechanism and financial incentives for high quality care. Timely initiation of PNC – which has been associated with improved maternal and infant health and utilization outcomes – is one of seventeen quality metrics for which CCOs can receive incentive payments. Objectives: The first objective of the current study was to estimate the impact of CCO implementation on the probability of initiating PNC in the first trimester, and on PNC adequacy among Oregon Medicaid beneficiaries. The second objective of the study was to determine if the implementation of CCOs influenced disparities in PNC utilization between Medicaid and privately-insured women, and between non-Hispanic White women and Hispanic/non-Hispanic Black women. Study Design: This quasi-experimental retrospective observational study drew from two data sources: Oregon Vital Records (Birth Certificate statistical files) from the department of Health Analytics of the Oregon state public health department and Washington State’s Linked Birth- CHARS (Comprehensive Hospital Abstract Reporting System) data from the Washington State department of health. A difference-in-differences approach examined PNC utilization before and after CCO implementation. Washington State served as the control group, as its Medicaid financing and delivery systems remained unchanged. Multivariable linear probability analysis was used to control for confounding factors, including maternal age, race/ethnicity, education, parity, marital status, smoking history, previous preterm birth, and maternal morbidity. Population Studied: All births in Oregon and Washington from 2008 – 2013, which were covered by either Medicaid or private insurance, were included in the analysis. Since CCOs started operating mid-year in 2012, June through December 2012 was considered a transition period and births during this period were excluded from the analysis. Principal Findings: CCO implementation was associated with a significant increase in the probability of PNC initiation in the first trimester and a reduction in insurance-type disparities in first trimester PNC initiation and PNC adequacy among Oregon Medicaid beneficiaries. Racial/ethnic disparities did not change following CCO implementation. Conclusions: The implementation of CCOs in Oregon had a positive impact on the timeliness of PNC initiation among Medicaid beneficiaries, and also reduced disparities in PNC quality between Medicaid and privately-insured women. Implications for Policy or Practice: The ongoing health system transformation in Oregon provides an ideal setting to assess the impact of a novel health service delivery model on PNC utilization. If Oregon is successful in this bold and unprecedented move, it could serve as a model for other Medicaid and commercial health plans seeking to improve PNC quality. Further study on the longer-term effects of CCO implementation on PNC quality as well as the effect of CCOs on other health care domains, is warranted. Close

• 13118. [Article] Cruise ship disturbance to Kittlitz's murrelets (Brachyramphus brevirostris) in Glacier Bay National Park and Preserve, Alaska

  The Kittlitz's murrelet (Brachyramphus brevirostris), a small pursuit-diving seabird in the family Alcidae, occurs across much of coastal Alaska and parts of the Russian Far East. Glacier Bay National ...

  Citation × Citation Citation Abstract Copy Title: Cruise ship disturbance to Kittlitz's murrelets (Brachyramphus brevirostris) in Glacier Bay National Park and Preserve, Alaska Author: Marcella, Timothy K. The Kittlitz's murrelet (Brachyramphus brevirostris), a small pursuit-diving seabird in the family Alcidae, occurs across much of coastal Alaska and parts of the Russian Far East. Glacier Bay National Park, located in Southeast Alaska, is believed to support approximately 37% of the worldwide breeding population of Kittlitz's murrelets during the summer months. Recent concern over apparent population declines in Alaska, coupled with the Park's dual mandate of resource preservation and visitation, led to this study. Cruise ships, although not the most numerous vessel type operating in Glacier Bay, have previously been identified as the vessel type eliciting the greatest disturbance response from Kittlitz's murrelets. During the murrelet breeding seasons in 2011 and 2012, my field assistants and I collected focal observations of 4,251 Brachyramphus murrelets from the bow of cruise ships traveling through Glacier Bay. Identification of murrelets to species was hampered by both the distance at which murrelets responded to the approaching ship and the type of response to the ship (diving vs. flushing). For roughly 40% of focal observations of murrelets from cruise ships, the species of murrelet (Kittlitz's murrelet or marbled murrelet [B. marmoratus]) could not be identified. Apparent habitat partitioning by the two murrelet species in Glacier Bay resulted in 79% of identified murrelets in the upper section of the Bay (Upper Bay) being Kittlitz's murrelets, while 83% of identified murrelets in the lower section of the Bay (Lower Bay) were marbled murrelets. In the Upper Bay, cruise ships are predicted to disturb 61% of all murrelets within 850 m on either side of the cruise ship's course (i.e., elicited a flushing or diving response), whereas in the Lower Bay, cruise ships are predicted to disturb 72% of murrelets within 850 m of the ship's course. Using Cox multistate models, I demonstrated that murrelets in the Upper Bay (predominantly Kittlitz's murrelets) were more likely to dive than flush in response to approaching cruise ships, whereas murrelets in the Lower Bay (predominantly marbled murrelets) were more likely to flush than dive. Also, murrelets in the Upper Bay responded to cruise ships by flushing or diving at shorter distances from the ship compared to murrelets in the Lower Bay. Murrelets in both areas of Glacier Bay generally reacted to cruise ships at greater distances when the ship approached indirectly, presumably because of the larger profile presented by a passing ship as opposed to a directly advancing ship. Absolute distance of the cruise ship from a focal murrelet was a strong predictor of murrelet disturbance response; no other management-relevant covariates that were measured during this study (e.g., ship velocity, distance to shore, whether a cruise ship had entered the Bay earlier that day) explained a significant proportion of the variation in murrelet response. Inferences based on data collected on-board cruise ships were limited to murrelet disturbance responses that occurred within 1 km of the ship. This was because of limits to the distance from the ship at which behavioral responses could be observed and the a priori assumption that disturbance to murrelets by cruise ships was unlikely at distances greater than 1 km. Results from shipboard observations indicated that some proportion of murrelets encountered at the farthest distance we could make inferences were on occasion disturbed (point estimate at 850 m perpendicular distance from ship's course = 15-30% probability of flushing or diving). This suggests that disturbance of murrelets by cruise ships in Glacier Bay exceeded expected distance thresholds. In order to investigate the effects of cruise ships on murrelet behavior at distances greater than 1 km, my assistants and I collected a total of 643 focal observations of Kittlitz's murrelets during 181 hours of observation from land-based observation sites in the Upper Bay during the 2012 field season. By combining these data with AIS and GPS ship tracks, I was able to append distance to the nearest cruise ship to each focal murrelet observation and search for patterns in murrelet behavior. By collecting data in this manner, I was able to avoid biasing the study based on pre-conceived notions of what constituted a threshold distance for cruise ships to disturb Kittlitz's murrelets. Using a segmented regression model within a logistic regression framework, I found that Kittlitz's murrelets exhibited a disturbance threshold (defined as an increased incidence of flushing from the water) by cruise ships at distances of at least 1.6 km, and perhaps as great as 6.0 km, with a best estimate of threshold disturbance distance at 3.8 km from a cruise ship. When cruise ships were greater than 3.8 km from focal Kittlitz's murrelets, the baseline probability of murrelets flushing during a focal observation period was 12.5%. When cruise ships were less than 3.8 km from focal Kittlitz's murrelets, the probability of flushing increased logistically with decreasing distance to an estimated 48% for the closest approach distances. The unexpectedly long distances at which murrelet behavior was affected by cruise ships in Glacier Bay is most likely attributable to social facilitation by other disturbed murrelets, because similar numbers of murrelets flushed when cruise ships were approaching (n = 30) as when they were receding (n = 27). Once a Kittlitz's murrelet flushed from the water, the subsequent duration of flight did not vary with distance to the nearest cruise ship. Instead, the duration of Kittlitz's murrelet flight was associated with time of day. The strong association between the proximity of cruise ships and the probability of a murrelet flushing, even at distances of several kilometers, demonstrates that Kittlitz's murrelets in Glacier Bay are susceptible to disturbance from cruise ships at distances greater than has previously been published for any seabird. Title: Cruise ship disturbance to Kittlitz's murrelets (Brachyramphus brevirostris) in Glacier Bay National Park and Preserve, Alaska Author: Marcella, Timothy K. The Kittlitz's murrelet (Brachyramphus brevirostris), a small pursuit-diving seabird in the family Alcidae, occurs across much of coastal Alaska and parts of the Russian Far East. Glacier Bay National Park, located in Southeast Alaska, is believed to support approximately 37% of the worldwide breeding population of Kittlitz's murrelets during the summer months. Recent concern over apparent population declines in Alaska, coupled with the Park's dual mandate of resource preservation and visitation, led to this study. Cruise ships, although not the most numerous vessel type operating in Glacier Bay, have previously been identified as the vessel type eliciting the greatest disturbance response from Kittlitz's murrelets. During the murrelet breeding seasons in 2011 and 2012, my field assistants and I collected focal observations of 4,251 Brachyramphus murrelets from the bow of cruise ships traveling through Glacier Bay. Identification of murrelets to species was hampered by both the distance at which murrelets responded to the approaching ship and the type of response to the ship (diving vs. flushing). For roughly 40% of focal observations of murrelets from cruise ships, the species of murrelet (Kittlitz's murrelet or marbled murrelet [B. marmoratus]) could not be identified. Apparent habitat partitioning by the two murrelet species in Glacier Bay resulted in 79% of identified murrelets in the upper section of the Bay (Upper Bay) being Kittlitz's murrelets, while 83% of identified murrelets in the lower section of the Bay (Lower Bay) were marbled murrelets. In the Upper Bay, cruise ships are predicted to disturb 61% of all murrelets within 850 m on either side of the cruise ship's course (i.e., elicited a flushing or diving response), whereas in the Lower Bay, cruise ships are predicted to disturb 72% of murrelets within 850 m of the ship's course. Using Cox multistate models, I demonstrated that murrelets in the Upper Bay (predominantly Kittlitz's murrelets) were more likely to dive than flush in response to approaching cruise ships, whereas murrelets in the Lower Bay (predominantly marbled murrelets) were more likely to flush than dive. Also, murrelets in the Upper Bay responded to cruise ships by flushing or diving at shorter distances from the ship compared to murrelets in the Lower Bay. Murrelets in both areas of Glacier Bay generally reacted to cruise ships at greater distances when the ship approached indirectly, presumably because of the larger profile presented by a passing ship as opposed to a directly advancing ship. Absolute distance of the cruise ship from a focal murrelet was a strong predictor of murrelet disturbance response; no other management-relevant covariates that were measured during this study (e.g., ship velocity, distance to shore, whether a cruise ship had entered the Bay earlier that day) explained a significant proportion of the variation in murrelet response. Inferences based on data collected on-board cruise ships were limited to murrelet disturbance responses that occurred within 1 km of the ship. This was because of limits to the distance from the ship at which behavioral responses could be observed and the a priori assumption that disturbance to murrelets by cruise ships was unlikely at distances greater than 1 km. Results from shipboard observations indicated that some proportion of murrelets encountered at the farthest distance we could make inferences were on occasion disturbed (point estimate at 850 m perpendicular distance from ship's course = 15-30% probability of flushing or diving). This suggests that disturbance of murrelets by cruise ships in Glacier Bay exceeded expected distance thresholds. In order to investigate the effects of cruise ships on murrelet behavior at distances greater than 1 km, my assistants and I collected a total of 643 focal observations of Kittlitz's murrelets during 181 hours of observation from land-based observation sites in the Upper Bay during the 2012 field season. By combining these data with AIS and GPS ship tracks, I was able to append distance to the nearest cruise ship to each focal murrelet observation and search for patterns in murrelet behavior. By collecting data in this manner, I was able to avoid biasing the study based on pre-conceived notions of what constituted a threshold distance for cruise ships to disturb Kittlitz's murrelets. Using a segmented regression model within a logistic regression framework, I found that Kittlitz's murrelets exhibited a disturbance threshold (defined as an increased incidence of flushing from the water) by cruise ships at distances of at least 1.6 km, and perhaps as great as 6.0 km, with a best estimate of threshold disturbance distance at 3.8 km from a cruise ship. When cruise ships were greater than 3.8 km from focal Kittlitz's murrelets, the baseline probability of murrelets flushing during a focal observation period was 12.5%. When cruise ships were less than 3.8 km from focal Kittlitz's murrelets, the probability of flushing increased logistically with decreasing distance to an estimated 48% for the closest approach distances. The unexpectedly long distances at which murrelet behavior was affected by cruise ships in Glacier Bay is most likely attributable to social facilitation by other disturbed murrelets, because similar numbers of murrelets flushed when cruise ships were approaching (n = 30) as when they were receding (n = 27). Once a Kittlitz's murrelet flushed from the water, the subsequent duration of flight did not vary with distance to the nearest cruise ship. Instead, the duration of Kittlitz's murrelet flight was associated with time of day. The strong association between the proximity of cruise ships and the probability of a murrelet flushing, even at distances of several kilometers, demonstrates that Kittlitz's murrelets in Glacier Bay are susceptible to disturbance from cruise ships at distances greater than has previously been published for any seabird. Close

• 13119. [Article] Abrupt deglacial climate changes in the North Pacific and implications for climate tipping points

  Paleoclimate archives have revealed abrupt climate events that are superimposed on more gradual climate changes throughout the last glacial and deglacial periods. The underlying causes of such rapid climate ...

  Citation × Citation Citation Abstract Copy Title: Abrupt deglacial climate changes in the North Pacific and implications for climate tipping points Author: Praetorius, Summer Kate Paleoclimate archives have revealed abrupt climate events that are superimposed on more gradual climate changes throughout the last glacial and deglacial periods. The underlying causes of such rapid climate changes are still poorly understood, but the strong expression of these events in northern hemisphere records likely points to climatic mechanisms of a northern origin. A leading hypothesis for the trigger of these climate fluctuations has been changes in the strength of the Atlantic meridional overturning circulation (AMOC). However, the very rapid nature of some of the observed climate transitions (3-50 years) suggests a potential role for abrupt shifts in atmospheric circulation or nonlinear feedbacks within the climate system. Understanding the relative timing and magnitude of these events in different regions of the globe will help to identify the sources and possible amplifying mechanisms that have led to abrupt climate changes in the past, which will provide insight and constraints on the potential for abrupt climate changes in the future. This dissertation seeks to characterize climate changes occurring in the Northeast Pacific during the last deglaciation, a time period that encompasses the dynamic transition between the last ice age and the modern day interglacial period. So far, high-resolution records with precise chronologies from the North Pacific have been sparse, and paleoclimate models and proxy reconstructions disagree about the deglacial climate changes that are both predicted and observed to have occurred in this region. Marine sediment records from the Gulf of Alaska (GOA) have exceptionally high resolution (~1 cm/yr), making it possible to reconstruct climate changes in unprecedented detail for the North Pacific region. We establish new multi-decadal scale records of surface ocean variability using planktonic oxygen isotopes and sea-surface temperature (SST) estimates based on the alkenone U₃₇[superscript K'] unsaturation index, as well as regional records of ice-rafting and deglacial volcanic activity sourced from the Mt. Edgecumbe volcanic field (MEVF). The age models for these records are constrained by high-precision radiocarbon dating, tephra correlation, and "tuning" to the decadal-scale North Greenland Ice Core Project (NGRIP) oxygen isotope record. We combine new and previously published data from a depth transect of marine sites in the GOA and Northeast Pacific to place surface ocean changes in context of oceanic variability throughout the water column. These reconstructions are then used to evaluate three fundamental questions: 1) what are the timing and patterns of deglacial climate changes in the North Pacific relative to other regions, 2) what are the potential forcing mechanisms for deglacial climate variability in this region, and 3) how does the subsurface ocean respond to and influence abrupt climate change. In chapter two, we compare the timing and patterns of climate changes occurring between the North Pacific and North Atlantic regions. A major debate in the paleoclimate literature has been whether these regions operate in a synchronized or seesaw like mode. We compare the high resolution GOA and NGRIP oxygen isotope records as proxies for local temperature, and find that both synchronous and asynchronous climate patterns occur between regions throughout the past 18,000 years. The most abrupt climate transitions are preceded/accompanied by synchronous behavior, whereas times of relative climate stability exhibit asynchronous or anticorrelated (seesaw) patterns. This implies that coupling of North Pacific and North Atlantic heat transport could act as an amplifying mechanism in abrupt northern hemisphere climate change, whereas opposing oceanic regimes could act to balance northern hemisphere heat transport, and thus promote climate stability. In chapter three, we examine the timing between regional deglaciation and volcanism to evaluate potential feedbacks between climate and volcanic activity. Although volcanic eruptions have been observed to contribute to abrupt climate fluctuations with global effects in historical times, the role of volcanic forcing in climate variability of the more distant past (prior to the Holocene) has been neglected due to the very short-time scales in which volcanic events occur, and the difficulty of obtaining records with high enough resolution to capture these events and their associated climate effects. We evaluate the source and timing of a sequence of 23 tephra layers preserved in high-accumulation rate sediment cores proximal to the MEVF, and examine the regional climate response to this volcanic activity through comparison with reconstructions of sea surface temperatures, oxygen isotopes, and the δ¹⁸O of seawater. We find that the onset of enhanced volcanic activity coincides with abrupt warming at the onset of the Bølling Allerød, regional retreat of glaciers, and a period of rapid vertical land motion predicted from a model of regional isostatic rebound. These finding support the hypothesis that deglaciation may promote volcanism by removing crustal loading. The records of sea surface variability show large fluctuations during the episode of intense volcanic activity, suggesting that deglacial volcanic activity may not only respond to climate, but may also contribute to climate variance during the deglacial interval. In Chapter four, we examine the oceanographic changes that lead to two episodes of hypoxia in the GOA that lasted for millennia during the deglaciation. Similar hypoxic events have been documented across the North Pacific, indicating a widespread expansion of the oxygen minimum zone (OMZ) during the Bølling Allerød and early Holocene warm periods. These episodes have been linked to enhanced export productivity in many sites, however, the driving mechanisms for enhanced productivity and ocean deoxygenation remain elusive. Our alkenone temperature reconstructions reveal two abrupt warmings of 4-5°C that precisely coincide with the onset of increased export productivity and a sudden shift to hypoxic conditions, suggesting a strong link between ocean warming, marine productivity, and deoxygenation. Oxygen isotopes throughout the water column indicate that a transient subsurface warming of ~2°C might have accompanied the first hypoxic event during the BA. We propose that abrupt ocean warming lead to an expansion of the North Pacific OMZ through a reduction in oxygen solubility, enhanced thermal stratification, and a stimulation of marine productivity through the stabilization of the euphotic zone (related to stratification), combined with enhanced nutrient input from remobilization of iron in hypoxic shelf sediments. These studies indicate that large surface and subsurface ocean changes occurred in the North Pacific during the last deglaciation, with the potential for important feedbacks on global climate. Title: Abrupt deglacial climate changes in the North Pacific and implications for climate tipping points Author: Praetorius, Summer Kate Paleoclimate archives have revealed abrupt climate events that are superimposed on more gradual climate changes throughout the last glacial and deglacial periods. The underlying causes of such rapid climate changes are still poorly understood, but the strong expression of these events in northern hemisphere records likely points to climatic mechanisms of a northern origin. A leading hypothesis for the trigger of these climate fluctuations has been changes in the strength of the Atlantic meridional overturning circulation (AMOC). However, the very rapid nature of some of the observed climate transitions (3-50 years) suggests a potential role for abrupt shifts in atmospheric circulation or nonlinear feedbacks within the climate system. Understanding the relative timing and magnitude of these events in different regions of the globe will help to identify the sources and possible amplifying mechanisms that have led to abrupt climate changes in the past, which will provide insight and constraints on the potential for abrupt climate changes in the future. This dissertation seeks to characterize climate changes occurring in the Northeast Pacific during the last deglaciation, a time period that encompasses the dynamic transition between the last ice age and the modern day interglacial period. So far, high-resolution records with precise chronologies from the North Pacific have been sparse, and paleoclimate models and proxy reconstructions disagree about the deglacial climate changes that are both predicted and observed to have occurred in this region. Marine sediment records from the Gulf of Alaska (GOA) have exceptionally high resolution (~1 cm/yr), making it possible to reconstruct climate changes in unprecedented detail for the North Pacific region. We establish new multi-decadal scale records of surface ocean variability using planktonic oxygen isotopes and sea-surface temperature (SST) estimates based on the alkenone U₃₇[superscript K'] unsaturation index, as well as regional records of ice-rafting and deglacial volcanic activity sourced from the Mt. Edgecumbe volcanic field (MEVF). The age models for these records are constrained by high-precision radiocarbon dating, tephra correlation, and "tuning" to the decadal-scale North Greenland Ice Core Project (NGRIP) oxygen isotope record. We combine new and previously published data from a depth transect of marine sites in the GOA and Northeast Pacific to place surface ocean changes in context of oceanic variability throughout the water column. These reconstructions are then used to evaluate three fundamental questions: 1) what are the timing and patterns of deglacial climate changes in the North Pacific relative to other regions, 2) what are the potential forcing mechanisms for deglacial climate variability in this region, and 3) how does the subsurface ocean respond to and influence abrupt climate change. In chapter two, we compare the timing and patterns of climate changes occurring between the North Pacific and North Atlantic regions. A major debate in the paleoclimate literature has been whether these regions operate in a synchronized or seesaw like mode. We compare the high resolution GOA and NGRIP oxygen isotope records as proxies for local temperature, and find that both synchronous and asynchronous climate patterns occur between regions throughout the past 18,000 years. The most abrupt climate transitions are preceded/accompanied by synchronous behavior, whereas times of relative climate stability exhibit asynchronous or anticorrelated (seesaw) patterns. This implies that coupling of North Pacific and North Atlantic heat transport could act as an amplifying mechanism in abrupt northern hemisphere climate change, whereas opposing oceanic regimes could act to balance northern hemisphere heat transport, and thus promote climate stability. In chapter three, we examine the timing between regional deglaciation and volcanism to evaluate potential feedbacks between climate and volcanic activity. Although volcanic eruptions have been observed to contribute to abrupt climate fluctuations with global effects in historical times, the role of volcanic forcing in climate variability of the more distant past (prior to the Holocene) has been neglected due to the very short-time scales in which volcanic events occur, and the difficulty of obtaining records with high enough resolution to capture these events and their associated climate effects. We evaluate the source and timing of a sequence of 23 tephra layers preserved in high-accumulation rate sediment cores proximal to the MEVF, and examine the regional climate response to this volcanic activity through comparison with reconstructions of sea surface temperatures, oxygen isotopes, and the δ¹⁸O of seawater. We find that the onset of enhanced volcanic activity coincides with abrupt warming at the onset of the Bølling Allerød, regional retreat of glaciers, and a period of rapid vertical land motion predicted from a model of regional isostatic rebound. These finding support the hypothesis that deglaciation may promote volcanism by removing crustal loading. The records of sea surface variability show large fluctuations during the episode of intense volcanic activity, suggesting that deglacial volcanic activity may not only respond to climate, but may also contribute to climate variance during the deglacial interval. In Chapter four, we examine the oceanographic changes that lead to two episodes of hypoxia in the GOA that lasted for millennia during the deglaciation. Similar hypoxic events have been documented across the North Pacific, indicating a widespread expansion of the oxygen minimum zone (OMZ) during the Bølling Allerød and early Holocene warm periods. These episodes have been linked to enhanced export productivity in many sites, however, the driving mechanisms for enhanced productivity and ocean deoxygenation remain elusive. Our alkenone temperature reconstructions reveal two abrupt warmings of 4-5°C that precisely coincide with the onset of increased export productivity and a sudden shift to hypoxic conditions, suggesting a strong link between ocean warming, marine productivity, and deoxygenation. Oxygen isotopes throughout the water column indicate that a transient subsurface warming of ~2°C might have accompanied the first hypoxic event during the BA. We propose that abrupt ocean warming lead to an expansion of the North Pacific OMZ through a reduction in oxygen solubility, enhanced thermal stratification, and a stimulation of marine productivity through the stabilization of the euphotic zone (related to stratification), combined with enhanced nutrient input from remobilization of iron in hypoxic shelf sediments. These studies indicate that large surface and subsurface ocean changes occurred in the North Pacific during the last deglaciation, with the potential for important feedbacks on global climate. Close

• 13120. [Article] Restoring the Columbia River Estuary : Chinook Salmon Recovery and Invasive Species Management

  As highlighted in this study, shallow-water habitats and the prey they provide are important for juvenile salmon in the Columbia River estuary, but the spread of invasive species and large-scale changes ...

  Citation × Citation Citation Abstract Copy Title: Restoring the Columbia River Estuary : Chinook Salmon Recovery and Invasive Species Management Author: Klopfenstein, Rachael As highlighted in this study, shallow-water habitats and the prey they provide are important for juvenile salmon in the Columbia River estuary, but the spread of invasive species and large-scale changes to the estuary influence how these habitats are utilized. Reed canarygrass (Phalaris arundinacea) (“PHAR” hereafter) is a highly invasive aquatic plant species that affects a number of emergent wetland habitats in the upper Columbia River estuary, and is of concern to those trying to restore important shallow-water habitats for juvenile salmon. The presence of PHAR undoubtedly reduces plant diversity, but this study seeked to elucidate how PHAR affects juvenile Chinook Salmon rearing success relative to natural emergent vegetation. The study further evaluated the importance of wetland-deriver prey to juveniles found in shallow-water habitats along a habitat gradient (i.e., back-water channel, confluence, and main stem). We conducted research at a floodplain wetland restoration site in the tidal-fluvial portion of the estuary, where a water control structure is used to manage water levels and the spread of PHAR. The goal of the research was to compare two microhabitats within the floodplain: areas dominated by PHAR and areas dominated by natural emergent vegetation. Using hatchery-raised juvenile Chinook salmon, we designed a series of feeding experiments in artificial enclosures to determine whether invasive PHAR and natural emergent vegetation provide similar foraging and growth opportunities for juvenile salmon. We further identified differences in physical and biological parameters of each habitat (e.g., temperature, dissolved oxygen, and invertebrate community) and examined feeding characteristics (e.g., diet composition and modeled growth rates) for juveniles through a stomach content analysis. Additionally, we conducted beach seining and diet analysis for fish collected along a habitat gradient and compared the diet composition and modeled growth rates between the sample areas. In the floodplain wetland, invertebrate prey compositions from the 2015-2016 (March- June) fallout and emergence traps were similar, but prey abundances and diversity varied seasonally. Across both years, for emergence traps, the average total density (per m²) of invertebrates in the natural vegetation and in PHAR was 154±18 m² and 225±34 m², respectively, and for the fallout traps was 664±95 m² and 662±64 m², respectively. Salmon diets were mostly similar, and a large proportion of diets in both habitats were made up of Copepoda/Cladocera (60-98% composition by biomass). Growth during the net pen experiment differed significantly between the two vegetation types (Kruskal-Wallis: p<0.001), with fish growing more in the natural emergent vegetation. In 2015, juveniles grew an average 6.4 mm FL in the natural emergent vegetation, compared to 4.7 mm FL in PHAR, and consumed fewer Copepoda/Cladocera and more Diptera over the 10 days. In 2016, juveniles grew an average 9.2 mm FL in the natural emergent vegetation compared to 7.6 mm FL in PHAR. In 2016, fish from both habitats consumed a higher abundance of Copepoda/Cladocera and grew more, despite poor water quality conditions at the site. Of the subyearlings (n=170) and yearlings (n=14) collected in habitats adjacent to the floodplain wetland, 48% were of known hatchery origin. Modeled potential growth rates for subyearlings were similar on average between February and May in the back channel, confluence, and main stem, ranging from 0.067–0.07 g/g/d, but the rates varied seasonally. Growth potential was higher in the back channel habitat earlier in the sampling season (February-March), as the modeled daily growth rates were 0.08 g/g/d compared to 0.06 g/g/d in the main stem. All fish collected prior to May were relatively small and unclipped, highlighting the seasonal benefits of shallow-water habitats to support a variety of life-history traits. When comparing modeled growth rates of the juveniles reared at the floodplain wetland compared to the in adjacent habitats, estimates from the floodplain wetland were higher across all months. Restoration of shallow-water habitats is important for the overall health of the estuary, but the effects of large-scale ecosystem changes (e.g., flow regulation and spread invasive species) on salmon recovery and estuary-management decisions are uncertain. For example, water control structures to limit the spread of PHAR also reduce fish access to floodplain habitats, and fewer high-flow events further limit fish access and may facilitate the spread of invasive species. PHAR has been shown to reduce overall plant diversity and, as observed in this study, may provide habitat that is less suitable to juvenile Chinook Salmon. The high density of important prey for salmon found at the site, regardless of the presence of PHAR, and high potential growth measured at the site, emphasize the importance of restoring shallow-water habitats that are accessible to juvenile Chinook Salmon in the upper estuary. Title: Restoring the Columbia River Estuary : Chinook Salmon Recovery and Invasive Species Management Author: Klopfenstein, Rachael As highlighted in this study, shallow-water habitats and the prey they provide are important for juvenile salmon in the Columbia River estuary, but the spread of invasive species and large-scale changes to the estuary influence how these habitats are utilized. Reed canarygrass (Phalaris arundinacea) (“PHAR” hereafter) is a highly invasive aquatic plant species that affects a number of emergent wetland habitats in the upper Columbia River estuary, and is of concern to those trying to restore important shallow-water habitats for juvenile salmon. The presence of PHAR undoubtedly reduces plant diversity, but this study seeked to elucidate how PHAR affects juvenile Chinook Salmon rearing success relative to natural emergent vegetation. The study further evaluated the importance of wetland-deriver prey to juveniles found in shallow-water habitats along a habitat gradient (i.e., back-water channel, confluence, and main stem). We conducted research at a floodplain wetland restoration site in the tidal-fluvial portion of the estuary, where a water control structure is used to manage water levels and the spread of PHAR. The goal of the research was to compare two microhabitats within the floodplain: areas dominated by PHAR and areas dominated by natural emergent vegetation. Using hatchery-raised juvenile Chinook salmon, we designed a series of feeding experiments in artificial enclosures to determine whether invasive PHAR and natural emergent vegetation provide similar foraging and growth opportunities for juvenile salmon. We further identified differences in physical and biological parameters of each habitat (e.g., temperature, dissolved oxygen, and invertebrate community) and examined feeding characteristics (e.g., diet composition and modeled growth rates) for juveniles through a stomach content analysis. Additionally, we conducted beach seining and diet analysis for fish collected along a habitat gradient and compared the diet composition and modeled growth rates between the sample areas. In the floodplain wetland, invertebrate prey compositions from the 2015-2016 (March- June) fallout and emergence traps were similar, but prey abundances and diversity varied seasonally. Across both years, for emergence traps, the average total density (per m²) of invertebrates in the natural vegetation and in PHAR was 154±18 m² and 225±34 m², respectively, and for the fallout traps was 664±95 m² and 662±64 m², respectively. Salmon diets were mostly similar, and a large proportion of diets in both habitats were made up of Copepoda/Cladocera (60-98% composition by biomass). Growth during the net pen experiment differed significantly between the two vegetation types (Kruskal-Wallis: p<0.001), with fish growing more in the natural emergent vegetation. In 2015, juveniles grew an average 6.4 mm FL in the natural emergent vegetation, compared to 4.7 mm FL in PHAR, and consumed fewer Copepoda/Cladocera and more Diptera over the 10 days. In 2016, juveniles grew an average 9.2 mm FL in the natural emergent vegetation compared to 7.6 mm FL in PHAR. In 2016, fish from both habitats consumed a higher abundance of Copepoda/Cladocera and grew more, despite poor water quality conditions at the site. Of the subyearlings (n=170) and yearlings (n=14) collected in habitats adjacent to the floodplain wetland, 48% were of known hatchery origin. Modeled potential growth rates for subyearlings were similar on average between February and May in the back channel, confluence, and main stem, ranging from 0.067–0.07 g/g/d, but the rates varied seasonally. Growth potential was higher in the back channel habitat earlier in the sampling season (February-March), as the modeled daily growth rates were 0.08 g/g/d compared to 0.06 g/g/d in the main stem. All fish collected prior to May were relatively small and unclipped, highlighting the seasonal benefits of shallow-water habitats to support a variety of life-history traits. When comparing modeled growth rates of the juveniles reared at the floodplain wetland compared to the in adjacent habitats, estimates from the floodplain wetland were higher across all months. Restoration of shallow-water habitats is important for the overall health of the estuary, but the effects of large-scale ecosystem changes (e.g., flow regulation and spread invasive species) on salmon recovery and estuary-management decisions are uncertain. For example, water control structures to limit the spread of PHAR also reduce fish access to floodplain habitats, and fewer high-flow events further limit fish access and may facilitate the spread of invasive species. PHAR has been shown to reduce overall plant diversity and, as observed in this study, may provide habitat that is less suitable to juvenile Chinook Salmon. The high density of important prey for salmon found at the site, regardless of the presence of PHAR, and high potential growth measured at the site, emphasize the importance of restoring shallow-water habitats that are accessible to juvenile Chinook Salmon in the upper estuary. Close