Graduation Year

2026

Document Type

Campus Only Senior Thesis

Degree Name

Bachelor of Science

Department

Environmental Analysis

Reader 1

Veronica Padilla Vriesman

Reader 2

Sarah Gilman

Abstract

Anthropogenic climate change is radically altering the movement and activity of pollutants in air, water, soil, and biological organisms, and heavy metals are pollutants of particular concern due to their toxicity, longevity, and potential for bioaccumulation. In southern California, one of the most obvious effects of climate change is an exponential increase in wildfire intensity and occurrence, which has led to a greater release of heavy metals such as lead, cadmium, chromium, copper, zinc, arsenic, manganese, and mercury into coastal environments. Monitoring efforts are becoming increasingly important as wildfire-related heavy metals threaten environmental and human health, and I sought to understand if California mussel (Mytilus californianus) tissue and shells can serve as biomarkers of heavy metal inputs to southern California coastal environments. To examine heavy metal concentrations in M. californianus tissue, I utilized a dataset from the decades-long National Mussel Watch and California State Mussel Watch monitoring programs and saw spikes in a variety of heavy metals in the 3-5 years following two of the four wildfires I investigated. To establish if M. californianus shells can be used as a longer-term record of heavy metals, I used LA-ICP-MS on mussels field sampled from the burn area of the 2025 Palisades Fire and saw a significant bump in lead and manganese in the growth rings calcified during the samples’ last 1-1.5 years of life. Given the temporal limitations of the Mussel Watch dataset and the small number of shells that were laser ablated these results should be interpreted with caution, but this is an encouraging step towards validating M. californianus for the environmental monitoring of heavy metals. Further research should focus on examining more recent mussel tissue to investigate a concerning increase in heavy metals since ~2007, running LA-ICP-MS on a greater number and variety of M. californianus shells, tuning LA-ICP-MS settings to detect lower levels of copper, zinc, and cadmium, and investigating M. californianus growth rates and stress responses to understand heavy metal uptake rates after fires.

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This thesis is restricted to the Claremont Colleges current faculty, students, and staff.

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