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• 2791. [Article] Specific consensus statement on the likely impacts of climate change on the Pacific Northwest

  The signatories of this statement seek to describe the state of scientific knowledge regarding likely impacts of climate change to the Pacific Northwest region. The intent is to assist Governor Kulongoski’s ...

  Citation × Citation Citation Abstract Copy Title: Specific consensus statement on the likely impacts of climate change on the Pacific Northwest The signatories of this statement seek to describe the state of scientific knowledge regarding likely impacts of climate change to the Pacific Northwest region. The intent is to assist Governor Kulongoski’s Advisory Group on Global Warming in its task of developing a greenhouse gas emission reduction strategy for Oregon. The signatories agree that climate change is underway and that it is having global effects as well as impacts in the Pacific Northwest region. Title: Specific consensus statement on the likely impacts of climate change on the Pacific Northwest The signatories of this statement seek to describe the state of scientific knowledge regarding likely impacts of climate change to the Pacific Northwest region. The intent is to assist Governor Kulongoski’s Advisory Group on Global Warming in its task of developing a greenhouse gas emission reduction strategy for Oregon. The signatories agree that climate change is underway and that it is having global effects as well as impacts in the Pacific Northwest region. Close

• 2792. [Article] The Anatomy of a Buried Submarine Hydrothermal System, Clark Volcano, Kermadec Arc, New Zealand

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the Society ...

  Citation × Citation Citation Abstract Copy Title: The Anatomy of a Buried Submarine Hydrothermal System, Clark Volcano, Kermadec Arc, New Zealand Author: Ditchburn, R. G., Walker, S. L., et al., Merle, S. G., de Ronde, C. E. J. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the Society of Economic Geologists and can be found at: http://economicgeology.org/. Title: The Anatomy of a Buried Submarine Hydrothermal System, Clark Volcano, Kermadec Arc, New Zealand Author: Ditchburn, R. G., Walker, S. L., et al., Merle, S. G., de Ronde, C. E. J. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the Society of Economic Geologists and can be found at: http://economicgeology.org/. Close

• 2793. [Article] Water and methanol adsorption on a series of organic complexes of montmorillonite

  Water and methanol adsorption isotherms at 25° and 37° C. were determined on a series of organo-bentonite clays. The clays differed in the length of the carbon chain attached to the amine adsorbed in the ...

  Citation × Citation Citation Abstract Copy Title: Water and methanol adsorption on a series of organic complexes of montmorillonite Author: Carter, Loren Sheldon Water and methanol adsorption isotherms at 25° and 37° C. were determined on a series of organo-bentonite clays. The clays differed in the length of the carbon chain attached to the amine adsorbed in the cation exchange position. The amines used had carbon chains of 4, 6, 8, 10, 12, 14, 16, and 18 carbon atoms. Nitrogen isotherms at -195.8 were also determined. The apparatus used was a gravemetric adsorption balance using quartz springs with a sensitivity of about one millimeter extension per milligram of load. The isotherms were typical type II isotherms and gave good B. E. T. plots. Effective surface areas were calculated from the B.E. T. plots. Isosteric heats of adsorption were calculated using the Clausius-Claperon equation, with data from the isotherms at the two temperatures. Title: Water and methanol adsorption on a series of organic complexes of montmorillonite Author: Carter, Loren Sheldon Water and methanol adsorption isotherms at 25° and 37° C. were determined on a series of organo-bentonite clays. The clays differed in the length of the carbon chain attached to the amine adsorbed in the cation exchange position. The amines used had carbon chains of 4, 6, 8, 10, 12, 14, 16, and 18 carbon atoms. Nitrogen isotherms at -195.8 were also determined. The apparatus used was a gravemetric adsorption balance using quartz springs with a sensitivity of about one millimeter extension per milligram of load. The isotherms were typical type II isotherms and gave good B. E. T. plots. Effective surface areas were calculated from the B.E. T. plots. Isosteric heats of adsorption were calculated using the Clausius-Claperon equation, with data from the isotherms at the two temperatures. Close

• 2794. [Article] Ecology of Corydalis aquae-gelidae, a rare riparian plant

  Corydalis aquae-gelidae is a large herbaceous perennial in the Fumariaceae that has high habitat specificity. It is endemic to the western Cascade Range of Oregon and Washington, almost entirely on the ...

  Citation × Citation Citation Abstract Copy Title: Ecology of Corydalis aquae-gelidae, a rare riparian plant Author: Goldenberg, Douglas M. Corydalis aquae-gelidae is a large herbaceous perennial in the Fumariaceae that has high habitat specificity. It is endemic to the western Cascade Range of Oregon and Washington, almost entirely on the Mt. Hood and Gifford Pinchot National Forests. It is a federal C2 candidate under the Endangered Species Act and a Forest Service sensitive species. This study included a niche analysis, i.e., defining the levels of environmental factors where Corydalis aquaegelidae grew, and relating its abundance to environmental variation, using data from the southwestern Mt. Hood National Forest. Corydalis grew in relatively cool habitats (between late June and early September, diurnal means were 17.7°C for air temperature, 9.7°C for water temperature, and 10.6°C tor substrate temperature). Elevations were from 460 to 1300 m, on streams from headwaters to the fifth order Clackamas River. The stream reaches occupied by Corydalis had relatively small seasonal fluctuations in flow. An estimated 90% of the plants on the Oak Grove Fork were submerged yearly, and about 75% of the plants were between average summer low water level and winter high water level. The abundance of Corydalis aquae-gelidae was modeled using principal components analysis, resulting in a reproduction index (based on the number of seedlings and juveniles) and a biomass index (from the number of adults, their average leaf numbers and height, and percent cover). The abundance of Corydalis was greatest within 5 cm vertical distance below to 20 cm above the summer water levels, and within 150 cm horizontal distance to the water. Optimal water cover was within 10 to 30%. Abundance decreased with increasing organic material and fines (material <2mm) substrate cover. Optimal mineral and moss cover were 25 to 50% and 50 to 80% respectively. Abundance increased with increasing gravel and cobble cover. Abundance was suppressed where canopy cover was below 20%. GS substrates (gravel and coarse sand) were most favorable, followed by GX substrates (gravel and sand dominant, with other materials), then LX substrates (soil or mud dominant). Emergence from seeds and rootstocks occurred in late May and early June. Plants farther from the water flowered later than those closer to or in the water. Senescence occurred in late August to mid-September. Temperature differences and phenological state differences were generally greater within sites than across the elevational gradient. Corydalis aquae-gelidae seeds required 6 to 7 months of stratification before germination in the laboratory. Under lab conditions, cold substrates (less than 5.8°C AM low, 12.6°C PM high) reduced growth of Senecio triangularis seedlings, but not of Corydalis. Corydalis seedlings grew as rapidly in a greenhouse as in the field, but warmer, drier treatments produced less rapid growth than cool treatments with saturated substrates. Corydalis aquae-gelidae had relatively high allocation to roots, and slightly below average reproductive allocation, compared to data for other herbaceous species in the literature, including species from the same region. Development was slow; an estimated 8 years were required for reproductive maturity. Using a growth model and growth stage data from the field, a population age structure was hypothesized. Based on this age structure, Corydalis reproduction appeared to be adequate for population maintenance. Seed dispersal was mainly by explosive dehiscence and flowing water. Corydalis aquae-gelidae was pollinated by bumblebees (Apidae). VA mycorrhizae were present but infrequent in the juveniles and seedlings investigated. Slugs were the most frequent cause of herbivore damage. Downy mildew (Peronospora) occurred at relatively low elevations and under relatively low canopy cover. Both competition with and niche differentiation among streamside species were thought to occur. Corydalis aquae-gelidae appeared to be a relatively late-successional plant. The range of Corydalis aquae-gelidae may be restricted by dispersal problems, rather than by unfavorable environments, as apparently suitable habitat existed beyond its range. Timber harvest and road building have damaged Corydalis aquae-gelidae populations through direct physical disturbance and habitat degradation. Water diversion for the Stone Creek Hydropower Project should lead to loss of plants from the large Oak Grove Fork populations through drought and other habitat changes. Fisheries habitat improvement projects and grazing may also threaten Corydalis populations. Title: Ecology of Corydalis aquae-gelidae, a rare riparian plant Author: Goldenberg, Douglas M. Corydalis aquae-gelidae is a large herbaceous perennial in the Fumariaceae that has high habitat specificity. It is endemic to the western Cascade Range of Oregon and Washington, almost entirely on the Mt. Hood and Gifford Pinchot National Forests. It is a federal C2 candidate under the Endangered Species Act and a Forest Service sensitive species. This study included a niche analysis, i.e., defining the levels of environmental factors where Corydalis aquaegelidae grew, and relating its abundance to environmental variation, using data from the southwestern Mt. Hood National Forest. Corydalis grew in relatively cool habitats (between late June and early September, diurnal means were 17.7°C for air temperature, 9.7°C for water temperature, and 10.6°C tor substrate temperature). Elevations were from 460 to 1300 m, on streams from headwaters to the fifth order Clackamas River. The stream reaches occupied by Corydalis had relatively small seasonal fluctuations in flow. An estimated 90% of the plants on the Oak Grove Fork were submerged yearly, and about 75% of the plants were between average summer low water level and winter high water level. The abundance of Corydalis aquae-gelidae was modeled using principal components analysis, resulting in a reproduction index (based on the number of seedlings and juveniles) and a biomass index (from the number of adults, their average leaf numbers and height, and percent cover). The abundance of Corydalis was greatest within 5 cm vertical distance below to 20 cm above the summer water levels, and within 150 cm horizontal distance to the water. Optimal water cover was within 10 to 30%. Abundance decreased with increasing organic material and fines (material <2mm) substrate cover. Optimal mineral and moss cover were 25 to 50% and 50 to 80% respectively. Abundance increased with increasing gravel and cobble cover. Abundance was suppressed where canopy cover was below 20%. GS substrates (gravel and coarse sand) were most favorable, followed by GX substrates (gravel and sand dominant, with other materials), then LX substrates (soil or mud dominant). Emergence from seeds and rootstocks occurred in late May and early June. Plants farther from the water flowered later than those closer to or in the water. Senescence occurred in late August to mid-September. Temperature differences and phenological state differences were generally greater within sites than across the elevational gradient. Corydalis aquae-gelidae seeds required 6 to 7 months of stratification before germination in the laboratory. Under lab conditions, cold substrates (less than 5.8°C AM low, 12.6°C PM high) reduced growth of Senecio triangularis seedlings, but not of Corydalis. Corydalis seedlings grew as rapidly in a greenhouse as in the field, but warmer, drier treatments produced less rapid growth than cool treatments with saturated substrates. Corydalis aquae-gelidae had relatively high allocation to roots, and slightly below average reproductive allocation, compared to data for other herbaceous species in the literature, including species from the same region. Development was slow; an estimated 8 years were required for reproductive maturity. Using a growth model and growth stage data from the field, a population age structure was hypothesized. Based on this age structure, Corydalis reproduction appeared to be adequate for population maintenance. Seed dispersal was mainly by explosive dehiscence and flowing water. Corydalis aquae-gelidae was pollinated by bumblebees (Apidae). VA mycorrhizae were present but infrequent in the juveniles and seedlings investigated. Slugs were the most frequent cause of herbivore damage. Downy mildew (Peronospora) occurred at relatively low elevations and under relatively low canopy cover. Both competition with and niche differentiation among streamside species were thought to occur. Corydalis aquae-gelidae appeared to be a relatively late-successional plant. The range of Corydalis aquae-gelidae may be restricted by dispersal problems, rather than by unfavorable environments, as apparently suitable habitat existed beyond its range. Timber harvest and road building have damaged Corydalis aquae-gelidae populations through direct physical disturbance and habitat degradation. Water diversion for the Stone Creek Hydropower Project should lead to loss of plants from the large Oak Grove Fork populations through drought and other habitat changes. Fisheries habitat improvement projects and grazing may also threaten Corydalis populations. Close

• 2795. [Article] Epoxidation of cyclodiene compounds by rat liver microsomes

  Rat liver microsomes are shown to contain an enzyme system which converts the cyclodiene insecticides, aldrin, heptachlor and isodrin to their corresponding epoxides, dieldrin, heptachlor epoxide, and ...

  Citation × Citation Citation Abstract Copy Title: Epoxidation of cyclodiene compounds by rat liver microsomes Author: Wong, David Taiwai Rat liver microsomes are shown to contain an enzyme system which converts the cyclodiene insecticides, aldrin, heptachlor and isodrin to their corresponding epoxides, dieldrin, heptachlor epoxide, and endrin. The microsomal fraction of 450 milligrams of liver from male rats epoxidates 80 percent of a 20 to 50 microgram aldrin substrate in 20 minutes at 37°C. The pH optimum for these epoxidations is 8.2. The enzymatic activity of the microsomes is retained during two weeks storage at low temperatures. Isodrin, a stereoisomer of aldrin, is less readily oxidized (about 60 percent) under similar conditions. Only 40 percent conversion occurs in the case of heptachlor. Microsomes from female rats are about one-half as active in the conversions as those from males. The role of epoxidation as the first step in the metabolism of these compounds is discussed. Title: Epoxidation of cyclodiene compounds by rat liver microsomes Author: Wong, David Taiwai Rat liver microsomes are shown to contain an enzyme system which converts the cyclodiene insecticides, aldrin, heptachlor and isodrin to their corresponding epoxides, dieldrin, heptachlor epoxide, and endrin. The microsomal fraction of 450 milligrams of liver from male rats epoxidates 80 percent of a 20 to 50 microgram aldrin substrate in 20 minutes at 37°C. The pH optimum for these epoxidations is 8.2. The enzymatic activity of the microsomes is retained during two weeks storage at low temperatures. Isodrin, a stereoisomer of aldrin, is less readily oxidized (about 60 percent) under similar conditions. Only 40 percent conversion occurs in the case of heptachlor. Microsomes from female rats are about one-half as active in the conversions as those from males. The role of epoxidation as the first step in the metabolism of these compounds is discussed. Close

• 2796. [Article] Space-charge-limited currents in silicon using gold contacts

  The theoretical characteristics of space-charge-limited currents in solids are reviewed, and a survey of suitable dielectric materials and experimental space-charge-limited devices is presented. The properties ...

  Citation × Citation Citation Abstract Copy Title: Space-charge-limited currents in silicon using gold contacts Author: Ede, Alan Winthrop The theoretical characteristics of space-charge-limited currents in solids are reviewed, and a survey of suitable dielectric materials and experimental space-charge-limited devices is presented. The properties of the gold-silicon contact as used in space-charge-limited devices were experimentally investigated. It was found that the observed characteristics could be explained on the basis that the gold diffuses far enough into the silicon under fabrication temperatures to set up a region of traps, which reduces the space-charge-limited component of current to a very low value. An attempt to fabricate planar space-charge-limited triodes using silicon as the dielectric and gold as the source and drain contacts was unsuccessful. Title: Space-charge-limited currents in silicon using gold contacts Author: Ede, Alan Winthrop The theoretical characteristics of space-charge-limited currents in solids are reviewed, and a survey of suitable dielectric materials and experimental space-charge-limited devices is presented. The properties of the gold-silicon contact as used in space-charge-limited devices were experimentally investigated. It was found that the observed characteristics could be explained on the basis that the gold diffuses far enough into the silicon under fabrication temperatures to set up a region of traps, which reduces the space-charge-limited component of current to a very low value. An attempt to fabricate planar space-charge-limited triodes using silicon as the dielectric and gold as the source and drain contacts was unsuccessful. Close

• 2797. [Article] Finish drying of conditioned alfalfa hay at high temperatures

  Published October 1970. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catal...

  Citation × Citation Citation Abstract Copy Title: Finish drying of conditioned alfalfa hay at high temperatures Author: Weswig, Paul H. (Paul Henry), 1912-, Oregon State University. Agricultural Experiment Station, Cropsey, Myron George, 1910- Published October 1970. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalog Title: Finish drying of conditioned alfalfa hay at high temperatures Author: Weswig, Paul H. (Paul Henry), 1912-, Oregon State University. Agricultural Experiment Station, Cropsey, Myron George, 1910- Published October 1970. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalog Close

• 2798. [Article] Equilibria in the ion exchange systems H⁺¹-CS⁺¹, H⁺²-Sr⁺², H⁺¹-Ce⁺³, Cs⁺¹-Sr⁺², Sr⁺²-Ce⁺³, H⁺¹-Cs⁺¹-Sr⁺², H⁺¹-Cs⁺¹-Ce⁺³ and H⁺¹-Sr⁺²-Ce⁺³

  A new method for determining ion exchange equilibrium data by liquid scintillation counting of the equilibrated solution phase is described. This method has been applied to determine equilibria between ...

  Citation × Citation Citation Abstract Copy Title: Equilibria in the ion exchange systems H⁺¹-CS⁺¹, H⁺²-Sr⁺², H⁺¹-Ce⁺³, Cs⁺¹-Sr⁺², Sr⁺²-Ce⁺³, H⁺¹-Cs⁺¹-Sr⁺², H⁺¹-Cs⁺¹-Ce⁺³ and H⁺¹-Sr⁺²-Ce⁺³ Author: Meyer, Walter A new method for determining ion exchange equilibrium data by liquid scintillation counting of the equilibrated solution phase is described. This method has been applied to determine equilibria between Dowex 50W X8, a commercial strong cation exchange resin, and binary and ternary solution containing the varying combinations of H⁺¹, Cs⁺¹, Sr⁺² and Ce⁺³. Equilibrium isotherms at room temperature are presented for total solution normalities of 0.1, 0.5 and 1.5, 2.5 or 3.0 normal. These data are correlated and examined in terms of phase, chemical and Donnan equilibrium theories. Finally the feasibility of determining ternary equilibrium data from binary data is examined. Title: Equilibria in the ion exchange systems H⁺¹-CS⁺¹, H⁺²-Sr⁺², H⁺¹-Ce⁺³, Cs⁺¹-Sr⁺², Sr⁺²-Ce⁺³, H⁺¹-Cs⁺¹-Sr⁺², H⁺¹-Cs⁺¹-Ce⁺³ and H⁺¹-Sr⁺²-Ce⁺³ Author: Meyer, Walter A new method for determining ion exchange equilibrium data by liquid scintillation counting of the equilibrated solution phase is described. This method has been applied to determine equilibria between Dowex 50W X8, a commercial strong cation exchange resin, and binary and ternary solution containing the varying combinations of H⁺¹, Cs⁺¹, Sr⁺² and Ce⁺³. Equilibrium isotherms at room temperature are presented for total solution normalities of 0.1, 0.5 and 1.5, 2.5 or 3.0 normal. These data are correlated and examined in terms of phase, chemical and Donnan equilibrium theories. Finally the feasibility of determining ternary equilibrium data from binary data is examined. Close

• 2799. [Article] Fabric reinforcement of low embankments on soft foundations

  Nonlinear large deflection finite element analyses of a fabric reinforced embankment on muskeg were performed to predict fabric tension and the effect of fabric stiffness on embankment deflections. The ...

  Citation × Citation Citation Abstract Copy Title: Fabric reinforcement of low embankments on soft foundations Author: Greenway, Daryl Rodney Nonlinear large deflection finite element analyses of a fabric reinforced embankment on muskeg were performed to predict fabric tension and the effect of fabric stiffness on embankment deflections. The predicted fabric tensions were compared with the results of a sliding block analysis, and show this simple analysis requires further correlation to develop its applicability. Predicted fabric tensions increase directly with embankment deflection and fabric stiffness. Construction live loads produce the greatest embankment deflections and fabric tensions. Time and temperature effects were not considered. For the fabric stiffnesses studied, the presence of fabric does not significantly affect embankment deflections predicted by the finite element model. The beneficial effects of fabric reinforcement noted in field installations may result from the fabric providing continuity to the real embankment that is assumed in all the finite element analyses. Title: Fabric reinforcement of low embankments on soft foundations Author: Greenway, Daryl Rodney Nonlinear large deflection finite element analyses of a fabric reinforced embankment on muskeg were performed to predict fabric tension and the effect of fabric stiffness on embankment deflections. The predicted fabric tensions were compared with the results of a sliding block analysis, and show this simple analysis requires further correlation to develop its applicability. Predicted fabric tensions increase directly with embankment deflection and fabric stiffness. Construction live loads produce the greatest embankment deflections and fabric tensions. Time and temperature effects were not considered. For the fabric stiffnesses studied, the presence of fabric does not significantly affect embankment deflections predicted by the finite element model. The beneficial effects of fabric reinforcement noted in field installations may result from the fabric providing continuity to the real embankment that is assumed in all the finite element analyses. Close

• 2800. [Article] The ecology of ocean acidification : integrating the effects of pH variation among other environmental stressors on biogeography and organismal performance in rocky intertidal communities

  Ocean Acidification (OA) has emerged as a major threat to marine ecosystems, particularly regarding calcifying organisms. A growing body of literature describing laboratory investigations into pH stress ...

  Citation × Citation Citation Abstract Copy Title: The ecology of ocean acidification : integrating the effects of pH variation among other environmental stressors on biogeography and organismal performance in rocky intertidal communities Author: Rose, Jeremy M. Ocean Acidification (OA) has emerged as a major threat to marine ecosystems, particularly regarding calcifying organisms. A growing body of literature describing laboratory investigations into pH stress indicates broadly deleterious effects for calcifiers, but responses vary greatly across taxa and can be influenced by variations in other environmental characteristics. Scaling laboratory results to ecological performance is critical for understanding the impacts of OA on marine communities. One method that can be useful for elucidating these ecological impacts is to study organisms and communities in environments that naturally vary in pH. The California Current Large Marine Ecosystem (CCLME) is one such ecosystem in which pH varies both in space and over time, bathing intertidal communities in a mosaic of pH conditions. The dynamics of the CCLME during the upwelling season also drive biologically-relevant variation in productivity and temperature. My dissertation leverages variation in oceanographic processes along the CCLME to explore the potential for OA impacts on rocky intertidal community distributions and the performances of two major space occupiers in rocky intertidal communities. In Chapter 2, a series of large scale community surveys along the CCLME were re-examined to ask if distributions of calcifiers and their mineral forms differ whether these differences are linked to environmental conditions. The patterns of differential calcifier abundances that emerge may better inform studies into the potential community impacts of OA by highlighting regions where calcifiers are relatively diverse or replete. Although these patterns are partially driven by complex interactions among temperature, phytoplankton productivity and upwelling, much of the spatial variation in calcifier abundance remains unexplained, suggesting the need to better characterize the pH environment along this oceanographically-complex region. In Chapter 3, I explored the relative influence of the pH mosaic along the CCLME on performance of the California mussel, Mytilus californianus. When considered along with other known stressors such as temperature and chlorophyll-a variations, pH meaningfully contributed toward explaining variation in mussel growth, condition and shell thickness. Contrary to expectation, some aspects of mussel performance were enhanced at comparatively low pH sites. The potential implications of this work include mediation of pH stress by other environmental factors, energetic trade-offs between calcified and soft tissue development, a life history transition toward increased resilience, and genotypic or persistent phenotypic differences that integrate exposure history. In Chapter 4, I investigated the relative influence of natural pH variation on performance of the purple sea urchin, Strongylocentrotus purpuratus. As with the California mussel study in Chapter 3, aspects of sea urchin calcified structures were enhanced, not suppressed as expected, at sites with comparatively low pH, after considering the effects of algal consumption and mean temperature. The combined results of Chapters 3 and 4 underscore the complex interactions between multiple environmental stressors and organismal physiology, highlight the biological relevance of pH on ecological performance, and suggest that life in areas already subject to natural pH variation may have the adaptive capacity to persist under future conditions. Title: The ecology of ocean acidification : integrating the effects of pH variation among other environmental stressors on biogeography and organismal performance in rocky intertidal communities Author: Rose, Jeremy M. Ocean Acidification (OA) has emerged as a major threat to marine ecosystems, particularly regarding calcifying organisms. A growing body of literature describing laboratory investigations into pH stress indicates broadly deleterious effects for calcifiers, but responses vary greatly across taxa and can be influenced by variations in other environmental characteristics. Scaling laboratory results to ecological performance is critical for understanding the impacts of OA on marine communities. One method that can be useful for elucidating these ecological impacts is to study organisms and communities in environments that naturally vary in pH. The California Current Large Marine Ecosystem (CCLME) is one such ecosystem in which pH varies both in space and over time, bathing intertidal communities in a mosaic of pH conditions. The dynamics of the CCLME during the upwelling season also drive biologically-relevant variation in productivity and temperature. My dissertation leverages variation in oceanographic processes along the CCLME to explore the potential for OA impacts on rocky intertidal community distributions and the performances of two major space occupiers in rocky intertidal communities. In Chapter 2, a series of large scale community surveys along the CCLME were re-examined to ask if distributions of calcifiers and their mineral forms differ whether these differences are linked to environmental conditions. The patterns of differential calcifier abundances that emerge may better inform studies into the potential community impacts of OA by highlighting regions where calcifiers are relatively diverse or replete. Although these patterns are partially driven by complex interactions among temperature, phytoplankton productivity and upwelling, much of the spatial variation in calcifier abundance remains unexplained, suggesting the need to better characterize the pH environment along this oceanographically-complex region. In Chapter 3, I explored the relative influence of the pH mosaic along the CCLME on performance of the California mussel, Mytilus californianus. When considered along with other known stressors such as temperature and chlorophyll-a variations, pH meaningfully contributed toward explaining variation in mussel growth, condition and shell thickness. Contrary to expectation, some aspects of mussel performance were enhanced at comparatively low pH sites. The potential implications of this work include mediation of pH stress by other environmental factors, energetic trade-offs between calcified and soft tissue development, a life history transition toward increased resilience, and genotypic or persistent phenotypic differences that integrate exposure history. In Chapter 4, I investigated the relative influence of natural pH variation on performance of the purple sea urchin, Strongylocentrotus purpuratus. As with the California mussel study in Chapter 3, aspects of sea urchin calcified structures were enhanced, not suppressed as expected, at sites with comparatively low pH, after considering the effects of algal consumption and mean temperature. The combined results of Chapters 3 and 4 underscore the complex interactions between multiple environmental stressors and organismal physiology, highlight the biological relevance of pH on ecological performance, and suggest that life in areas already subject to natural pH variation may have the adaptive capacity to persist under future conditions. Close