UC Irvine

Climate change is rapidly altering ecosystems worldwide, particularly due to rising temperatures and extreme weather events. The impacts of climate change on ecological systems are profound, affecting ecosystems at multiple levels, from individual physiology to community structure and ecosystem function. Aquatic systems, especially rocky intertidal zones and montane ponds, are especially vulnerable to the effects of climate change. Long-term monitoring is a useful tool to detect changes in these variable ecosystems. Rocky intertidal zones have undergone long term biodiversity monitoring that could benefit from protocol assessments, while montane ponds have been largely understudied. This dissertation aims to explore the qualities of a successful monitoring program and the impacts of climate variation on montane ponds through field surveys and experimental approaches. Chapter 1 evaluates the effects of monitoring protocols on the ability to detect trends in long-term biodiversity data in the rocky intertidal of Cabrillo National Monument in San Diego, CA. Results emphasize the importance of protocol consistency and goal-oriented design for effective long-term monitoring. Chapter 2 investigates the drivers of thermal, chemical, and biotic dynamics in a four-year field survey of 30 montane ponds in the Sierra Nevada mountains of California. Results indicate that snowfall is a key driver of montane pond dynamics, similar to montane lakes. Relatively low snowfall decreased pond volume, which increased mean temperatures and thermal variability, increased nutrient concentrations, and increased zooplankton abundance. These ponds also mixed more frequently than other ponds of their size, suggesting that montane ponds do not fit previously defined pond paradigms. Chapter 3 examines the interactive effects of thermal variability and heatwaves on montane pond zooplankton communities and physiology through a mesocosm experiment. Results indicate that while community composition remained stable, individuals from recently thermally stable backgrounds responded physiologically to a heatwave, suggesting potential resilience to climate extremes. My thesis integrates multiple methods, including variation across space and time in the field, as well as experimental investigation, to contribute to the growing body of knowledge on the impacts of climate variability on vulnerable aquatic systems.