SURFACE WATER MICROBIOME RESPONSE TO PYROGENIC CARBON AFTER A WILDLAND-URBAN INTERFACE FIRE

The increase in wildfire season duration, severity, and frequency in wildland-urban interfaces (WUI) is a global concern due to expanding human development. Post-fire storms can introduce pulses of pyrogenic organic contaminants into surface waters, but the dynamics between microbial communities and pyrogenic contaminants in WUI post-fire storm runoff are less understood. We studied a stream adjacent to a WUI fire in Orange County, CA, for organic contaminants, microbial community composition, and their predicted function immediately after the fire and during the following winter storms. The first rains after the fire were of low intensity and showed the highest discharges of smaller polycyclic aromatic hydrocarbons (PAHs) of concern, including benzo[a]pyrene (54.2 ppb, 64.8 ppb) and benz[a]anthracene (1.27 ppb, 1.23 ppb). However, dissolved organic carbon discharge reached a maximum average loading rate of 11.2 g C/s during later severe rain events. PAH concentrations were strongly correlated with each other but not with carbon loading rate. PAH concentration patterns did not match turbidity data, suggesting turbidity may be a poor water quality indicator of pyrogenic carbon. Several microbial taxa known to degrade PAHs, including Acinetobacter, Sphingobium, Massilia, Chitinophagaceae, Pedobacter, and Sphingomonas, were differentially abundant during the rainy period. Additionally, predicted metabolic pathways related to PAH biodegradation and transformation products such as catechol and protocatechuate were significantly up-regulated directly downstream of the fire. These findings highlight how episodic fire events create contaminate pulses that drive shifts in microbial community function favoring putative PAH degrading microorganisms in storms months after the fire without additional remediation amendments.

Presentation Preference: Oral

Primary Presenter: Lyssa Morgan, University of California, Irvine (lemorgan@uci.edu)

Authors:

Lyssa Morgan, University of California, Irvine  (lemorgan@uci.edu)

Allison Tilzey, University of California, Irvine  (atilzey@uci.edu)

Jialin Dong, University of California, Irvine  (jialind2@uci.edu)

Maya El Ajouz, University of California, Irvine  (melajouz@uci.edu)

Cameron Daley, University of California, Irvine  (csdaley@uci.edu)

Christopher Olivares, University of California, Irvine  (ciom@uci.edu)