UC Davis

Wildfire is an important ecological disturbance in California that occurs in forested, urban and suburban areas. These fires generate biochar and other partially burned plant materials capable of entering urban and suburban aquatic environments. However, little is known about how biochar may interact with mosquitoes that utilize these aquatic habitats for reproduction. This thesis investigated the effects of wood derived biochar on Aedes aegypti across multiple stages of the mosquito life cycle, from oviposition site selection to larval development and adult physiology, while also examining changes in the microbial communities of larval rearing water. The first chapter reviews the current understanding of Aedes aegypti oviposition behavior and the sensory and environmental cues that influence female selection of oviposition sites. This review provides a framework for understanding how changes in aquatic habitat characteristics may alter oviposition behavior and highlights the importance of chemical, olfactory, visual, and microbial cues in site selection. The second chapter investigates the effects of wildfire and lab generated wood biochar on Aedes aegypti oviposition under laboratory and field conditions. Initial observations suggested that, contrary to the original hypothesis that biochar would repel ovipositing females, biochar associated water could increase egg deposition. Subsequent experiments examined the effects of biochar concentration, preparation, and the presence of other potential oviposition attractants. These experiments demonstrated that biochar can influence oviposition-site selection and provide evidence that wildfire-derived materials may alter the attractiveness of aquatic habitats to gravid females. The third chapter examines the effects of biochar exposure beyond oviposition behavior. Aedes aegypti larval development was assessed following exposure to biochar associated water, while metabolomic and lipidomic analyses were used to investigate changes in adult Aedes aegypti female physiology. The microbial communities of larval rearing water were also characterized to determine whether biochar was associated with changes in the aquatic microbial environment. Together, these analyses indicate that biochar exposure is associated with changes in Aedes aegypti larval development, adult female metabolism, and the aquatic microbial community composition of Aedes aegypti breeding sites. Collectively, this work demonstrates that biochar has the potential to influence Aedes aegypti at multiple stages of its life cycle. These findings provide a foundation for further investigation into how biochar, aquatic habitat characteristics, and microbial communities interact to influence mosquito ecology and behavior.