Climate change is directly impacting the services humans derive from the sea at an accelerated rate. Ocean warming and acidification (i.e., a decrease in ocean pH) are leading to modifications in population sizes and ecosystem functioning. The observed shifts in these higher order processes are a direct result of individuals’ responses (i.e., physiology, including metabolism, growth, calcification, and survival) occurring within communities. Natural variation in past environmental exposure experienced by individuals may lead to greater population resilience, or it may push individuals past physiological thresholds leading to increased sensitivity and vulnerability to climate change. Thus, we need to determine how individual-level physiological responses to climate change scale up to influence marine ecosystems. Rocky intertidal habitats are an ideal study system for evaluating the relationships between individual physiological responses, ecosystem functioning, and climate change. Tide pools possess unique thermal and pH environments and can be monitored under natural conditions or manipulated with field-experiments over daily and seasonal time scales, creating natural “experimental mesocosms”. In addition, many species within rocky intertidal habitats are exposed to environmental conditions close to their tolerance limits, increasing their potential vulnerability to climate change. In Chapter 1, by utilizing the unique thermal environments of tide pools, I showed that across small spatial scales (pools), thermal history influences thermal sensitivity of marine invertebrates for short-term time intervals (1-week and 1-day) and that this relationship differs seasonally and between species with differing traits, including mobility. This suggests that variability in thermal responses among individuals may allow for a natural buffer at a population level in response to climate change. Multiple stressors may affect individuals independently or interactively, amplifying or mitigating effects. Thus, to determine the impacts of climate change, in Chapter 2, I used a 6-month long field manipulation of ocean warming and acidification in tide pools. I examined the combined effects of warming and acidification on the shell structure (shell thickness and corrosion) and functional properties (shell strength) of the ecologically critical species, the Pacific blue mussel (Mytilus trossulus). Acidification led to thinner, weaker, and more corroded shells whereas combined warming and acidification resulted in an increase in shell strength. My results suggest that to some degree, warming may mitigate the negative impacts of acidification on this mollusk species. Lastly, in Chapter 3, I characterize how warming and acidification, individually and interactively, impact net ecosystem calcification and the individual and population-level mechanisms driving impacts on net ecosystem calcification. Net ecosystem calcification tended to increase during the day and decrease at night; however, addition of CO2 during the hottest months led to decreased net ecosystem calcification and increased dissolution during both day and night. I found that individual mussel metabolic rates increased significantly in the presence of elevated CO2 and increased daily maximum of pool temperatures. Through this individual-level pathway, pH and temperature had a strong impact on the metabolic rates of individuals ultimately resulting in changes in net ecosystem calcification. On the other hand, greater mussel abundance was associated with increased net ecosystem calcification. Yet, with the addition of CO2, calcification decreased even in pools with the highest abundance of mussels, indicating that there are other pathways by which changes in pH can drive alterations in net ecosystem calcification. My dissertation reveals how species’ traits and natural thermal variation from short-term to seasonal time scales influence metabolic sensitivity to future warming among individuals (Ch. 1), independent climate stressors can negatively impact shellfish in situ, whereas the combined interactive effects between multiple stressors can lead to mitigation of the negative impacts of a single stressor alone (Ch. 2), and that ecosystem-level consequences of climate change are mediated by the abundance of dominant calcifiers and that this effect is dependent on the magnitude of acidification and warming (Ch. 3).

The oceans face increasing pressure from human activities. Land-based activities drive the runoff of pollutants into coastal waters where they can disturb or destroy natural habitat, while ocean-based activities can lead to the unsustainable extraction of marine resources, add additional pollutants, and disrupt biodiversity and ecosystem function. Yet, stewarding marine spaces intentionally can increase ecosystem function while deepening our understanding of these complex systems. Using a mix of spatial modeling and causal inference, the following dissertation, in three chapters, describes and presents solutions to improve stewardship of marine environments in the United States (US), considering our relationship with oceans from end to end. My first chapter describes and applies a novel tool to better understand the distribution of pollution from human activities, the second chapter proposes a strategy to mitigate the impacts of coastal nutrient pollution, and finally, my third chapter reveals key insights from our most intimate and foundational relationship with the ocean, our consumption of seafood. Each of these chapters is the product of long running, multi-disciplinary collaborations.

In the US, nitrate loading into marine environments has been relatively constant at a high input level over the past 20 years, while phosphate loading has continued to increase. In some places, excess nutrients drive cascading ecosystem changes, in others, despite significant additional nutrient loads, ecosystems are better able to absorb these impacts. In my first chapter, alongside collaborators, I identify pollution “hotspots” in continental US coastal waters where anthropogenic nutrient loading is high compared to natural nutrients in order to

help drive water quality management. We adapted generalized plume models for river and sewage to model the dispersal of anthropogenic nutrients into marine environments, we then combine model outputs with atmospheric N deposition, overlaying these with nutrient data from published sources (annual totals (kg/yr), 0.2 degree raster cell). We find nutrient pollution hotspots concentrated in the Northeast, US and in the Gulf of Mexico, however, some high-nutrient settings, like Southern California, have significant nutrient pollution in localized settings. This work contributes a novel application of generalized plume models that efficiently analyzes the transport and distribution of nutrient pollution at regional and national scales.

Given the severity of coastal nutrient loading, my second chapter explores a potential solution: strategic placement of seaweed aquaculture. Seaweed is capable of removing large quantities of nitrogen and phosphorus from coastal ecosystems, yet seaweed has gained little traction for its potential role in targeted nutrient assimilation. Marine nutrient pollution is increasing around the world, contributing to expanding eutrophic conditions and co-occurring with other stressors that impact the state and stability of aquatic ecosystems. In the US, climate change, legacy nitrogen, and nonpoint source pollution make it increasingly difficult to curb growing eutrophication and the associated effects, such as hypoxia (dissolved oxygen < 2 mgL-1). Employing a synthetic semi-quantitative approach, we use the Gulf of Mexico as a case study – a US priority area for aquaculture with substantial nutrient pollution and one of the largest hypoxic zones on the planet – to assess the potential for native seaweed

aquaculture to augment upstream pollution control with downstream nutrient assimilation. Results from this analysis suggest that given growing market demand, new product pathways, and nutrient pollution markets, seaweed aquaculture may be a feasible tool for nutrient assimilation that could subsidize, if not pay for itself.Finally, my third chapter explores the impact of consumption on marine resources. Shifts in food access due to the COVID-19 pandemic were heterogeneous, offering a unique chance to differentiate the effects of restaurants, public assistance programs, and consumer attitudes on purchasing behavior. We use California’s novel tiered COVID-19 restriction system, which imposed top-down county-level economic restrictions dependent on caseloads and testing rates, as a natural experiment to untether the effects of changing seafood access. We deployed a longitudinal survey (N=464) to capture seafood consumption patterns for the same population of Californians three times between August 2020 and August 2021. To casually identify marginal shifts in consumption behavior due to changing seafood access (i.e., food service restrictions and county-level factors) we use two-way fixed effects models. In parallel, we assess relationships between consumption at the species-level using network analyses. Nuanced purchasing behaviors, such as purchases of specific species (e.g. shrimp, salmon, and local species) and products (e.g. canned, fresh) became more entrenched given disruptions to access. Diversity of seafood consumption, however, remained unchanged from pandemic disruptions, shifting instead in response to individual attitudes. We find a personal relationship with seafood is the most pervasive driver of seafood consumption.

Superior mesenteric artery (SMA) syndrome is a rare cause of abdominal pain, nausea and vomiting that may be undiagnosed in patients presenting to the emergency department (ED). We report a 54-year-old male presenting to a community ED with abdominal pain and the subsequent radiographic findings.The patient’s computed tomgraphy (CT) of the abdomen and pelvis demonstrates many of the hallmark findings consistent with SMA syndrome, including; compression of the duodenum between the abdominal aorta and superior mesenteric artery resulting in intestinal obstruction, dilation of the left renal vein, and gastric distension. Patients diagnosed with SMA syndrome have a characteristically short distance between the superior mesenteric artery and the aorta (usually 2–8 mm) in contrast to healthy patients (10–34 mm). Our patient’s aortomesenteric distance was measured to be approximately 4 mm. Furthermore, the measured angle between the superior mesenteric artery and the aorta is reduced in patients withSMA syndrome from a normal range of 28°–65° to a measurement between 6°–22°. Our patient’s aortomesenteric angle was difficult to measure secondary to poor sagittal reconstructions, but appears to be approximately 30°. Following radiographic evidence suggesting SMA syndrome together with our patient’s constellation of presenting symptoms, a diagnosis of SMA syndrome was made and the patient was admitted to the general surgery service. However, our patient decided to leave against medical advice owing to improvement of his symptoms following the emptying of two liters of gastric contents via nasogastric tube evacuation. [West J Emerg Med. 2012;13(6):501-502]

Teachers are the foundation for effectively implementing personalized learning environments. This comparative case study investigated 16 teacher’s experiences with a personalized learning program by focusing on users of the Pinnacle Learning program at two, low-income school sites in southern California. This research’s conceptual framework is based upon Venkatesh and Davis’ (2000) determinants of perceived usefulness and Venkatesh and Bala’s (2008) determinants of perceived ease of use. Ultimately, this study reveals that in general teachers perceive personalized learning as relatively advantageous to their role in the classroom due to its fairly high level of ease and high level of usefulness, thus making teachers more likely to continue acceptance of this technology at their school sites.

During this study’s exploration of teacher beliefs about the Pinnacle Learning program, four specific areas were explored: training, use of program elements, classroom roles of teachers using a personalized learning program, and site implementation issues. By understanding teacher beliefs and attitudes on their use of and experience with personalized learning technology, this study was able to identify areas of concern that can be addressed and areas of strength that are beneficial to continue at each school site. Teacher input on the adoption of a personalized learning platform provides the often missing teacher voice from the research available on personalized learning. Input about how the role of teacher is changing may inform preparation programs and ongoing professional developments for teachers. Additionally, data from this research may help low SES schools who are considering the adoption of an online personalized learning platform as there have been limited studies which solely focus on this student demographic.

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