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Publication Date

Summer 2025

Degree Type

Thesis - Campus Access Only

Degree Name

Master of Science (MS)

Department

Moss Landing Marine Laboratories

Advisor

Sarah Smith; Holly Bowers; Thomas Connolly; Raphael Kudela

Abstract

Monterey Bay, CA is a highly productive system that is threatened by warming sea surface temperatures (SSTs) and the bloom forming genus Pseudo-nitzschia (Pn) that can produce the neurotoxin domoic acid (DA). Since half of Pn species produce DA, species-level identification is critical for predicting DA events. I determined whether temperature (12 °C, 15 °C, 20 °C, 25 °C, 30 °C) impacts P. pungens, P. multiseries, and P. australis growth, toxicity, and community composition in batch cultures measuring growth rate, biomass, cell physiology, and toxin production. In Part A, Pn strains were cultured individually at different temperatures to establish baseline growth curves to develop a predictive model for Pn species biomass. In Part B, a mixed community of Pn was grown at current Monterey Bay temperatures (15 °C). Increased temperatures led to increased growth rates, biomass, and toxin production. P. multiseries had a wider thermal range than P. pungens. When % relative initial biomass was equal, P. pungens and P. multiseries were predicted to reach maximum growth rates at 20.7 °C and 24.2 °C respectively. In a mixed community (15 °C), P. multiseries outcompeted P. australis and P. pungens based on cell concentration (cells μL-1). The observed species-specific thermal traits suggest that warming oceans may favor the dominance of toxic P. multiseries, thereby increasing the risk of DA events disrupting the marine ecosystem. This research furthers our understanding that temperature plays for forecasting species-specific toxic Pn blooms and mitigating their effects on marine life and coastal communities.

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