Kelp forests, like many marine ecosystems, are being exposed to more frequent and intense disturbances. Marine heatwaves are major drivers of widespread and sustained kelp forest losses, as temperature directly affects the distribution and persistence of populations. Heatwave effects have been examined on large scales using satellite-derived data, but there is also variability in kelp responses on local to regional scales, driven by marine microclimates such as localized upwelling. Field and drone-based monitoring efforts have been employed along the California coastline to capture local dynamics, but these surveys only cover spatially discrete samples from selected kelp beds. Consequently, field and drone-based datasets represent one end of the spatial spectrum for observing kelp canopy response and recovery after disturbance events, while satellite observations represent the other end. Neither method alone can fully resolve both local and regional to global-scale dynamics.The development of CubeSat constellations has enabled a workaround for these trade-offs, with global imagery available near-daily at meter-scale. In my first chapter, I develop methods to create spatially continuous time series of California kelp population dynamics from high-resolution CubeSat data. In my second chapter, I employ these time series to highlight local-scale variability in California kelp populations that have been impacted by marine heatwave events, helping to better identify areas of concern and understand the drivers of heatwave-mediated loss and stability. In my third chapter, I scale these methods to effectively map kelp canopy across the state of California. I develop deep learning models for estimating kelp canopy presence and apply these models to a time series of CubeSat data. My findings contribute new perspectives for addressing and understanding kelp forest disturbance regimes. Mapping kelp populations with CubeSat constellation data allowed for the identification of areas of vulnerability, providing utility in prioritizing areas for strategic protection and restoration. Classifying sections of coastline that supported kelp forests amidst marine heatwave events showed the presence of refugia, where subpopulations have been able to persist in habitats that are buffered from disturbance. Further, mapping these populations across California will allow for the development of new indicators of ecosystem functioning and health.

Satellite and aerial imagery have been used extensively for mapping the abundance and distribution of giant kelp (Macrocystis pyrifera) in southern California. While tides and currents have been shown to affect the amount of floating kelp canopy on the water surface, there have been no quantifications of how these processes can bias remotely sensed kelp estimates in this region. We used unmanned aerial vehicles (UAVs) to map fine-scale changes in canopy area due to tidal height and current speed at both Palos Verdes, CA and Santa Barbara, CA. Additionally, we collected a biweekly time series of kelp canopy area in Palos Verdes over the course of a year to monitor fine-scale, intra-seasonal changes in canopy coverage. Our automated method for detecting kelp canopy in color and multispectral UAV imagery was highly accurate (over 84% and 98%, respectively) in classifying exemplary kelp and water pixels across a range of weather, ocean, and illumination conditions. Increases in tidal height of 1 m reduced the amount of floating kelp canopy by 15% to 32%. Current speeds are generally low in southern California and had no statistically significant effect on apparent bed size. However, increases in current speeds of 0.1 m/s reduced the amount of floating kelp canopy by over 31%. Tidal height and current speed can introduce significant variability to estimates of kelp abundance, but the magnitude of this variability is region specific. The biweekly time series displayed intra-annual variability typical of giant kelp, with a relatively gradual decline in kelp canopy in late summer corresponding with high sea surface temperatures, a rapid decline in the winter associated with wave disturbance, and a gradual recovery in the spring of the following year. The time series was also able to capture intra-seasonal changes in kelp canopy area that would have gone undetected in an annual or quarterly dataset, namely an increase in area to about half of the maximum in the late fall before wave events began.

Climate change threatens the future of coastal wetlands, one of the most ecologicallyimportant, economically valuable ecosystems on earth. Changes to normal climatic and environmental conditions could throw off the delicate balance of these ecosystems with negative consequences to wetland biological response, productivity, and ultimately, resilience. Wetland response is controlled by biogeomorphic feedbacks relating plant productivity to environmental conditions, a complex interaction that can vary over space, within and among marshes, and over time, with tidal cycles and seasons. Wetland biomass serves as an important measure of spatiallyexplicit and temporally-variable changes that could ultimately impact wetland resiliency to climate change. Southern California’s coastal wetlands are especially threatened by climate change due to other anthropogenic forces like coastal squeeze by urban development. The combination of threats to these wetlands render them at-risk and call for improved understanding of how wetland response will vary across the region or within a given site as sea levels, precipitation, and temperatures change. Remote sensing, fieldwork, and habitat response modeling approaches were combined to gain a holistic perspective of wetland vulnerability and resiliency at scales ranging from plant response to regional overviews of habitat change. This approach also spans temporal scales to investigate climate-related changes over time by predicting future impacts, capturing current, highresolution patterns of biomass production, and uncovering decades of past patterns and drivers of wetland health. In chapter one, we develop a sea level rise (SLR) response model that addresses the scale‐dependent factors controlling SLR response and accommodates different levels of data availability to improve regional predictions of SLR vulnerability. In chapters two and three, we test the application of Unmanned Aerial Vehicles (UAVs) in remotely estimating aboveground biomass in coastal saltmarshes and how such hyperspatial insights can aid in satellite-based approaches to biomass estimation. Lastly, chapter four reveals temporal patterns of productivity in salt marshes spanning the region, allowing us to determine the importance of regional versus local climatic controls on saltmarsh productivity. By quantifying impacts across time and space, we gain a better understanding of how climate change will determine the fate of wetlands throughout southern California.

Early stages of cardiac development are well conserved among vertebrates. However, later morphological development results in a more complicated 4 chambered heart in mammals, while fish retain a simple two chambered heart. The onset of these morphological changes coincide with contribution of cells to the heart from the second heart field (SHF). Interestingly, despite the great morphological differences in the structures derived from precursors in the SHF in mammals and zebrafish, the signals regulating SHF development are conserved. Cardiac neural crest cells (CNCCs), which also contribute to later stages of cardiac development are well studied in chick and mouse models, but very little is known about the role of CNCCs in zebrafish heart development. It is possible that as with the SHF the molecular mechanisms of CNCC development is conserved among all vertebrates. In this study I aim to better define the role of CNCCs in zebrafish and determine how well the role for CNCCs is conserved. I show that there are two waves of CNCCs which contribute to the heart in zebrafish. The first invades the developing heart tube between 24 hpf and 30 hpf and gives rise to CNC derived cardiomyocytes. CNCCs with a myocardial fate have an invasive morphology as they enter the heart, and disrupt local adhesion molecules in neighboring cells. The second wave of CNCCs migrates along aortic arch artery 6, onto the ventral aorta by 80 hpf, and ultimately invades the BA. I find that both populations of CNC derived cells persist to adulthood. These two populations are separated not only by developmental time, but also by their response to FGF signaling as they migrate to the heart. The first wave is independent of Tbx1, and FGF signaling, and the second wave relies on FGF signaling for migration to the ventral aorta and BA. Ablation of NC leads to a variety of cardiac defects including reduced heart rate, defects in myocardial maturation, development of the BA and aorta, and defects in SHF contribution to the heart, as well as a dramatic increase of bmp4 expression, and a reduction of tbx1 expression. Many of the cardiac phenotypes I observe in NC ablated embryos are similar to those reported in other species, making zebrafish an ideal model to study signaling which may be important for CNC development in vertebrates.

Noxious stimuli are detected by primary afferent neurons of the dorsal root ganglia (DRG). Such neurons, known as nociceptors, can be divided into several distinct populations based on the heterogeneous distribution of receptors, ion channels, and neurotransmitters, however, functional correlates of these anatomical differences are yet unidentified. The work in this thesis further examines the neurochemical and functional segregation of nociceptor subtypes through a genetic and pharmacological investigation of neurons that express the heat and capsaicin receptor, TRPV1.

TRPV1 is activated by noxious heat stimuli (>43 ^oC), and is robustly expressed by primary afferent nociceptors. In addition, some have argued that TRPV1 is widely distributed in cells outside of the DRG, although there is considerable disagreement as to the extent and localization of this expression. To address this question, we generated a line of mice in which TRPV1+ cells co-express two reporter genes: placental alkaline phosphatase and nuclear lacZ. These enzymes allow for the sensitive and accurate identification of TRPV1+ cells and processes. Using this approach, we observed that, in contrast to numerous previous reports, TRPV1 expression in the nervous system is largely limited to peptidergic, primary afferent neurons. We additionally found evidence for TRPV1 in arteriolar smooth muscle cells, highlighting an important substrate for the actions of heat, protons, and other TRPV1 agonists on vascular tone.

We then investigated the relative contribution of TRPV1+ and TRPV1- nociceptors to the behavioral responses to stimuli of different pain modalities. Surprisingly, despite the fact that most nociceptors show polymodal response properties in electrophysiological assays, we found that pharmacological ablation of the central branches of TRPV1+ nociceptors selectively abolished heat pain sensitivity without altering behavioral responses to mechanical or cold stimuli. Conversely, we found that genetic ablation of nociceptors expressing the G protein-coupled receptor, MrgprD, which marks a large subset of TRPV1- DRG neurons, selectively reduced behavioral sensitivity to noxious mechanical stimuli. This double-dissociation suggests that the brain can distinguish different noxious stimulus modalities from the earliest stages of sensory processing as a result of distinct contributions from molecularly-defined nociceptor subtypes.

Mangroves are critical tropical coastal ecosystems and provide essential ecological and societal services. Mangroves have been rapidly changing over the last fifty years, and geospatial technologies provide a tool to measure such changes around the world. As a response to climate change and rising temperatures, mangroves have been encroaching into salt marshes at many mangrove-salt marsh ecotones in sub-tropical areas, rapidly shifting their distributions poleward. Although mangroves have faced substantial degradation and deforestation due to human activity, we have seen a rise in anthropological efforts towards their preservation and reforestation in recent years. This dissertation examines both climatic and anthropogenic drivers of change for mangrove ecosystems, using a combination of remote sensing, climate modeling, and manipulative experiments. First, we investigate mangrove range limit dynamics on the Atlantic and Pacific coasts of North America, where the same three species of mangroves are found. Using gridded climate data, remote sensing and manipulative experiments, we compared the realized and fundamental niches of the Atlantic and Pacific mangroves, and found notably different responses to environmental conditions, resulting in contrasting range dynamics. We then focused specifically on the Pacific range limit, where further manipulative experiments on cold water temperatures and aridity highlighted the fact that mangroves’ response to changes in climate is highly species- and location-specific. Therefore, aspects particular to each range population must be taken into consideration to best understand and predict mangrove response to climate change. Lastly, we focused on anthropogenic impacts on mangrove ecosystems. Using the island of Madagascar - a major biodiversity hotspot - as a case study, we conducted a remote sensing analysis of mangrove dynamics over fifty years. Results show that mangroves have faced considerable loss. However, recent awareness arising over the last twenty years has led to better conservation and preservation efforts, resulting in an increase in overall mangrove cover during this period.