UC Santa Barbara

As anthropogenic climate change destabilizes historical ecological regimes and drives more variable and extreme environments, species persistence may increasingly depend on inherent biological variation. Understanding how within-species trait variation mediates ecological resilience is essential for forecasting species responses under future climate scenarios. While ecological research often prioritizes responses at the species or community level, this dissertation centers intraspecific diversity as a potentially critical component of climate vulnerability in marine ecosystems. Specifically, I examine how trait variation within individuals and among populations influences organismal performance under climate stressors such as marine heatwaves and ocean acidification.Using an integrative approach that combines experimental ecology, observational biology, and open-source engineering, I investigate how individual- and population-level differences contribute to performance outcomes under environmental variability. In doing so, I address some technological and methodological challenges that constrain our ability to accurately capture the nuances of real-world environmental dynamics and measure organismal responses at ecologically relevant scales.To support these investigations, I developed two open-source tools: a programmable, automated temperature control system to replicate dynamic marine heatwaves in laboratory settings, and a low-cost, field-deployable pH sensor to enable greater accessibility to ocean acidification monitoring. I applied the marine heatwave simulator to assess within-population performance variation in the corallimorph Corynactis californica during a realistic marine heatwave, providing new insights into the climate sensitivity of a clonal species. Additionally, I expanded the research scope to examine between-population trait variation in the ecologically and economically important marine calcifier Siliqua patula, collaborating with coastal communities to ground the work in place-based knowledge and the social and cultural dimensions of climate vulnerability.From these studies, I documented ecologically significant trait variation across multiple scales, underscoring the role of intraspecific diversity in shaping ecological responses to environmental stochasticity. My findings reveal how existing methodological constraints can limit our understanding of ecological resilience to complex, real-world environmental stressors. By emphasizing within-species variation, this dissertation offers a framework for interpreting ecological responses to global change by linking environmental heterogeneity with intraspecific diversity. This work suggests that greater consideration of individual- and population-level diversity is essential for improving ecological forecasts in a rapidly changing world. By integrating ecological insights with accessible technologies, this dissertation advances a scalable and inclusive framework for understanding and enhancing adaptive capacity in marine ecosystems.