Abstract:

Harmful Algal Blooms (HABs) are a complex ecological phenomenon fueled by nutrient enrichment from natural and anthropogenic sources, driving rapid phytoplankton growth and causing ecosystem disruptions and public health risks. In California, HABs are predominantly caused by Pseudo-nitzschia spp., a diatom that produces domoic acid (DA)—a neurotoxin linked to Amnesic Shellfish Poisoning in humans and wildlife mortality. Despite extensive research, questions remain around the specific environmental triggers, nutrient interactions, and the influence of climate variability and human impact on these events.

In my thesis, I first examine 20 years of particulate DA and environmental data from Monterey Bay, Santa Barbara Channel, and San Pedro Channel, uncovering relationships between DA events, upwelling, nutrient availability, and climatic patterns like ENSO and PDO. Building on these findings, I used a 3D mechanistic model to explore DA production in the Southern California Bight, revealing how anthropogenic nutrient inputs amplify bloom frequency and intensity. Finally, I focus on nutrient pathways between San Francisco and Monterey Bay using a high-resolution model to quantify freshwater and wastewater nutrient fluxes’ impact on coastal productivity and HAB risks. Together, these studies demonstrate the cascading influence of land-derived nutrients and ocean conditions on DA HAB severity along California’s coast, providing insights to support management strategies for these critical marine areas.