Award: OCE-2306993

When wildfire smoke drifts over the ocean, what happens beneath the waves? This project explored how wildfire ash deposition affects marine microbes, the ocean's smallest yet most essential inhabitants. As wildfires become more frequent and widespread, understanding how smoke and ash influence ocean ecosystems is increasingly important for predicting changes in global carbon cycling and marine productivity.

Through field experiments along the California coast and in the North Pacific, the project tested how dissolved material leached from wildfire ash alters microbial growth and food-web dynamics. The results showed that ash-derived organic matter stimulated bacterial activity and dissolved organic matter remineralization rates. At the same time, grazing by microscopic predators declined while phytoplankton division rates remained stable, revealing a decoupling of predator-prey interactions that can lead to plankton accumulation following deposition events.

The study further demonstrated that the ocean's response to wildfire inputs depends more on the existing ecosystem state than on the chemical makeup of the ash itself. In low-biomass waters, bacteria rapidly consumed ash-derived organic matter, while in high-biomass waters it was less bioavailable and more likely to persist. Smaller phytoplankton cells increased in high-biomass settings with ash leachate additions, whereas larger cells became more prevalent in low-biomass waters. These patterns have implications for nutrient cycling, food-web structure, and carbon export to the deep ocean.

All datasets and analytical code from this research are publicly available through GitHub and the Biological and Chemical Oceanography Data Management Office (BCO-DMO), ensuring that these findings can inform future studies on ocean-climate interactions. Beyond the science, this fellowship supported undergraduate mentorship, helped launch a new graduate student in microbial oceanography, and contributed to Oregon State University's Microbiology summer camp for high-school students, thus broadening participation and curiosity about the connections between fire, microbes, and the sea.

 

Last Modified: 11/01/2025
Modified by: Nicholas Baetge