Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • BCO-DMO Processing Description
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

All surface seawater was collected just prior to local sunrise from a SBE-911+ Conductivity-Temperature-Depth (CTD, Sea-Bird Scientific) Niskin bottle rosette cast and then transferred or directly filtered into acid-cleaned 20-liter (L) carboys with platinum-cured silicone tubing.

Phytoplankton division and accumulation rates and zooplankton grazing rates (1/d) were estimated in 14 experiments, in which changes in group-specific phytoplankton cell abundances were measured using flow cytometry in a dilution series of total and filtered seawater after 24 hours (sampling at 0 hours and 24 hours). Phytoplankton apparent and instantaneous division rates, accumulation rates, and zooplankton grazing rates were quantified following Morison et al. (2019). For each experiment, 0.45-micrometer (µm) filtered seawater was generated directly from Niskin bottles using a polyethersulfone capsule filter (Polycap TC, Whatman) (Morison et al., 2019). Total seawater was diluted with the filtered seawater in 1-liter (L) acid-cleaned polycarbonate bottles to a final concentration of 100%, 75%, 50%, and 25% total seawater (Landry and Hassett, 1982). Each experiment included at least one biological replicate of one randomly selected dilution. Diluted water either remained unamended or was amended with ash leachate prior to being screened with mesh and incubated in a deck-board incubator with continuously flowing seawater. Ash leachates were added to a final amendment of ~4 micromoles carbon per liter (µmol C/L) as dissolved organic carbon (DOC). Incubations were screened to obtain a light level corresponding to the median intensity in the surface mixed layer.

- Imported original file "PHYTO_DILUTION.csv" into the BCO-DMO system.
- Flagged "NA" as a missing data value; missing data are empty/blank in the final CSV file.
- Saved final file as "953007_v1_phytoplankton_dilution_experiments.csv".

NSF Award Abstract:
Climate-driven warming is projected to increase the frequency, intensity, and size of wildfires that can have severe environmental, human, and economic impacts, particularly along the U.S. West Coast. These wildfires result in dramatic CO2 emissions and deposition of ash carrying nutrients, organic matter, and trace metals onto the coastal and open ocean. Deposition of wildfire ash on the ocean can alter the carbon and energy flow through marine food webs by fertilizing microbial production or inhibiting microbial growth due to heavy metal toxicity. How the character of both the ash (e.g., chemical quality, fertilizing v. toxic) and the starting microbial community composition (e.g., diversity, size distribution) influences the microbial response to ash-derived material is unknown. This project will address this knowledge gap by investigating the physiological responses of marine plankton off the U.S West Coast to different types of ash generated from local wildfires and plant biomass. This work will advance interdisciplinary science, bridging biological oceanography with terrestrial ecology and biogeochemistry, by generating foundational knowledge of wildfire impacts on surface ocean biology and carbon and energy transfer from land to ocean. Results from this project will enable improved forecasts of changes in marine ecosystems in response to wildfires, which is information pertinent to communities and industries that depend on ocean ecosystem resources, including fisheries. The work will also inform national efforts to mitigate and adapt to the impacts of climate change by addressing whether wildfire-stimulated fertilization and carbon fixation in the ocean can offset CO2 emissions from wildfires. This project will broaden participation and education in ocean science by providing immersive research experiences for multiple undergraduate students and opportunities for them to disseminate their work through scientific conferences and publications. Additionally, a day-long content unit related to the project will be developed and implemented in Oregon State University’s annual week-long Microbiology Summer Camp, which provides local high school students with a hands-on learning experience in microbiology.

Specifically, this project consists of mechanistic studies designed to quantitatively describe the physiological responses (e.g., growth, productivity, cellular stoichiometry) of phytoplankton and bacterioplankton to a variety of ash types. The quantity and proportion of nutrients, organic matter, and trace metals leached from ash into seawater likely depends on the quality of the ash, which is influenced by vegetation type and the temperature at which the ash was produced. This study will assess how microbial production and growth are fertilized or inhibited by the composition of ash and will consist of two primary elements. In the first element, ash will be collected from the field and generated in the lab from plant biomass. The ash will then be leached in seawater and chemically characterized for inorganic and organic matter content. In the second element, seawater incubation experiments will be conducted to quantify physiological and diversity-based responses of naturally occurring phytoplankton and bacterial communities to different ash types. Data generated from this project will contribute to improved predictive models of wildfire-driven material transfer from the terrestrial system to the ocean and its impact on carbon and energy flow in marine food webs.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.