Wildfire Ash Promotes Growth of Santa Barbara Channel Phytoplankton Communities Under Low Nutrient Conditions

On December 4, 2017, one of the largest California wildfires in modern history, termed the Thomas Fire, began and eventually burned over 280,000 acres and destroyed more than 1000 structures until it became fully contained on January 12, 2018. Throughout the course of the fire, smoke and ash caused unprecedented hazardous and unhealthy air quality conditions across Ventura and Santa Barbara counties and created a sustained plume that blanketed the coastal communities and coastal ocean. This plume led to the persistent deposition of ash extending more than 1000 km offshore near the Santa Barbara Channel. Although these large fires have become a common occurrence locally as well as across the state of California, no previous work has been done to understand how fires impact our coastal marine ecosystems. Through seasonal incubation experiments, natural phytoplankton communities were exposed to Thomas Fire ash leachate to explore how atmospheric deposition of ash may impact primary producers at different times of the year. During this presentation, results of this work including the impacts of ash on seawater chemistry, changes in phytoplankton growth and community composition, and implications of ash deposition in the marine environment will be discussed.