Ash to Algae: Tracing the Connection between Wildfires & Harmful Algal Blooms

I’m Brandon, a senior at California State Polytechnic University, Pomona, majoring in environmental biology. This past summer I had the pleasure of working in the Hutchin/Fu Lab as part of the Wrigley Institute’s REU program, researching with my mentor Bradley Mackett how the rainwater runoff from the Palisades wildfire could have influenced the Pseudo-nitzschia bloom in February of this year. 

Pseudo-nitzschia is a genus of marine diatom is native to California consisting of about 60 species worldwide with less than half producing the neurotoxin domoic acid (DA). Despite this algal group being so small, their impact is felt by many as DA bioaccumulates throughout food webs during bloom events, causing Amnesic Shellfish Poisoning in marine organisms and humans. These harmful algal blooms (HABs) are caused by seasonal upwelling, which is when prevailing winds in the spring months push away warm nutrient depleted water from the coast, being replaced with cold sediment rich water from below. This natural oscillation is crucial for our ecosystem as blooms of algal species are the basis for most marine food webs. This seasonality is important for HAB prediction so that we can take the necessary steps to protect our ecosystems.

What if this seasonality was influenced by an outside source? That is the question Bradley and I asked this summer when examining Pseudo-nitzschia’s response to nutrients introduced to coastal waters both naturally, through ash from the Palisades wildfire, and artificially, through the application of the fire-retardant PHOS-CHEK (PC). Previous studies have looked at wildfire’s impact on terrestrial waters and non-HAB forming marine communities. What we wanted to know is did the wildfire cause an earlier than expected HAB by stimulating a Pseudo-nitzschia bloom, and if it did, how did DA production change compared to a typical upwelling event?

We achieved this by culturing Pseudo-nitzschia in five 2-liter bottles (plus one control) and spiked them once with varying concentrations of PC (3 replicates per treatment). We also did this same experiment at the Wrigley Marine Science Center on a natural community to compare to our Pseudo-nitzchia cultures. These 2-liter bottles were filtered for DA, phosphate, nitrogen, biogenic silica, and other indicators to do a more complete analysis at a later date. We also looked at how ash may alleviate iron-limitation symptoms in Pseudo-nitzschia. Iron limitation causes Pseudo-nitzschia to produce more DA, so if ash alleviated these symptoms we could look towards other trace metals/nutrient limitations for the increase in toxicity in February. 

Analyzing the data from our experiments revealed that Pseudo-nitzschia showed the ability to grow in PC over an extended period, with the control group and higher concentrations showed decreasing growth rates towards the end of the batch experiment, however these were just general trends and not conclusive evidence. We also found no difference between DA production in our highest concentration treatment and our control group, however due to sporadic cell counts this comparison is inconclusive, so PC may still increase cellular toxicity in Pseudo-nitzchia as well as improve growth rates over time. Our Iron limitation and natural community batch culture yielded more promising results. Pseudo-nitzschia did grow better in cultures without iron, but added ash, compared to purely iron limited cultures, for conclusive evidence on if ash can relieve symptoms of limitation, Bradley will continue the experiment by adding ash to the pure iron limited cultures to see if they bounce back. Our natural community experiment gave us conclusive evidence that our ‘midrange’ concentrations increase biomass of diatom communities compared to the control and higher concentrations. Whether the experiments were conclusive or not matters little, because all this information is valuable for assessing how wildfires influence HABs and the microbial ecology of the San Pedro Channel. 

In hindsight sure, it’s clear how we could have handled our experiments to get more usable data, and it pains me to feel like I wasted even a day not being in the lab! This is to say, I know I want to do research, I want to go back into the field and collect more diatom samples, I want to go back into the lab and spend hours filtering out seawater, and I even want to count more cells under a microscope despite my eyes aching afterwards. I am proud to have been able to make any impact on the scientific community, and I want to keep making small impacts like this until I can eventually become the mentor and pass on the knowledge I have to the next generation of scientists. 

I originally didn’t think I would enjoy working in a biogeochemistry lab. I was a forestry major in community college, and when I transferred to Cal Poly Pomona, I was sure I would stick to that. However, I’ve slowly moved toward the marine side of conservation, then from the macro world to the micro world. While I still don’t have a set research focus, I hope to continue going through the motions, changing interests until I find what I truly want to do. It’s taken me this far already and I don’t see myself stopping anytime soon.