Project: RAPID: Biogeochemical effects of fire ash deposition to the coastal ocean, in response to the 2017 Southern California fires

NSF Award Abstract:

Massive wildfires in coastal regions cause ash to fall into the ocean, with unknown impacts. Ash contains chemical elements and materials that can encourage the growth of microscopic organisms in the surface ocean. The Thomas Fire has burned over 240,000 acres in southern California since Dec 4, 2017. The winds have carried a plume of smoke, ash and soot more than 1000 km over the Santa Barbara Channel. The intellectual merit of this RAPID project focuses on the impact of fire ash supply to coastal ocean ecosystems, by studying the 2017 Thomas Fire. This is achieved through a combination of experiments and environmental measurements, including an oceanographic expedition to the affected area aboard the R/V Sally Ride. The broader impacts of this award include the shipboard training of more than twelve graduate students as well as providing insight as to effects of the Thomas Fire on the coastal ocean.

Massive wildfires can couple terrestrial ecosystems to coastal ocean ecosystems through depositional and runoff processes. The Thomas Fire, which began on Dec 4, 2017, has burned over 240,000 acres and the persistent offshore winds created a plume of smoke, ash and soot that extended over 1000 km off shore. This unfortunate circumstance provides an opportunity to investigate the impact of ash deposition on the coastal ocean. This research entails a series of incubation experiments and measurements designed to assess the impact of fire ash deposition on the biogeochemistry of the coastal ocean. Specifically, the research tests the hypothesis that the deposition of wildfire-derived particulate matter to the coastal ocean impacts the planktonic communities of the upper water column, providing nutrients that facilitate blooms of phytoplankton, leaching dissolved organic carbon to surface waters that feeds heterotrophic bacterial populations, and serving as a source of sinking particulate matter that feeds heterotrophic bacterial populations deeper in the water column. These hypotheses are tested through a series of experiments at sea and in the home laboratories, and through shipboard measurements and analysis of samples collected from impacted waters.