How Fertilizer Runoff Feeds Coastal Harm and How Ocean Friendly Gardens Can Help
After a heavy rain, stormwater flows into storm drains, and most of us don’t think about where it goes afterward. The average resident rarely thinks about the effects of stormwater, which often contains fertilizer runoff from lawns or gardens, and eventually reaches coastal waters. The runoff contributes to algal blooms, oxygen depletion, and even takes marine life. California has been rapidly urbanizing for years, which, combined with annual droughts and extreme rain events, amplifies the issue of fertilizer runoff and the impacts on our coastal waters.
The reason why most people don’t think about this is that fertilizers are meant to aid garden and plant growth, so why would they hurt the very natural world that they’re meant to help? Runoff that contains ammonia from fresh manure, commonly used as a fertilizer, can be highly toxic and lethal even at relatively low levels of concentration. In addition, most chemical fertilizers contain nitrogen or phosphorus, excess of which can cause nutrient pollution in water. Nutrient overload can trigger ecosystem shifts, including changes in species diversity and harmful algal blooms.
The effects of harmful algal blooms were seen this spring when hundreds of sea lions were reportedly stranded and poisoned as a direct result of toxic algae blooms off the coast of Southern California. As the toxins produced by algae move up the food chain, these blooms can threaten the lives of sea lions, common dolphins, whales, and other marine mammals. While many factors led to the scale of this year’s harmful algal bloom event, excess nutrients from stormwater runoff can ultimately contribute to an imbalance in nearshore environments.
The impact goes beyond marine life, too. People are affected by beach closures and unsafe swimming water that poses health threats. Furthermore, the resulting fish or shellfish contamination also means that the very food we eat can contain toxins, so multiple fisheries were closed during this year’s harmful algal bloom event.
Certain organizations have already been working to fight this impact of stormwater, rescuing poisoned sea lions and studying possible mitigation solutions. In reality, this is an issue present in most regions that use fertilizers and receive rainfall. The prevalence of the matter means that it’s up to all communities, not just a handful of organizations, to mitigate the effects.
Few individuals have the power to revitalize ocean habitats or reduce excess chemicals in the waters. However, there are a number of other accessible ways to help. Homeowners are especially important in this fight due to the lack of filtration systems between your lawn and the ocean. It’s often disregarded or forgotten that storm drains lead directly to the ocean, meaning that all the chemicals in runoff go directly into the waves of your local beach. The best way to solve this issue is by addressing it directly in your backyard.
Surfrider’s Ocean Friendly Gardens program is dedicated to sustainable landscaping and education to reduce harmful runoff, preventing the issue directly at the source. They offer solutions and aim to spread awareness, protecting coastal health and resilience. For example, the program details the watershed approach to landscaping and how to reroute your downspout, two of the many accessible ways you can make a positive impact at home.
Crafting an Ocean-Friendly Garden or altering an existing garden to be more sustainable can be budget-friendly and within reach for all communities. Check if your garden is ocean-friendly through Surfrider and get started on helping the cause today. If many yards become ocean-friendly, it can help keep the oceans and marine life healthy and thriving. Every storm is a chance for pollution, but also an opportunity to protect the coast.
Sources:
Lopata, Jason. “L.A. Urbanized: Introduction.” Urbanize LA, 2 Apr. 2018, la.urbanize.city/post/la-urbanized-introduction.
Keena, Mary, et al. “Environmental Implications of Excess Fertilizer and Manure on Water Quality.” NDSU Agriculture and Extension, North Dakota State University, 31 Oct. 2017, www.ndsu.edu/agriculture/extension/publications/environmental-implications-excess-fertilizer-and-manure-water-quality.
Shen, Qirong, et al. “Chemical Fertilizer - an Overview | ScienceDirect Topics.” ScienceDirect, 2022, www.sciencedirect.com/topics/agricultural-and-biological-sciences/chemical-fertilizer.
“Coastal Pollution Tutorial: NOAA’s National Ocean Service Education.” National Ocean Service, oceanservice.noaa.gov/education/tutorial-coastal/harmful-algal-blooms/habs01-sub-02.html.
“Early Bloom of Toxic Algae off Southern California Sickens Hundreds of Sea Lions and Dolphins.” National Oceanic and Atmospheric Administration, 26 Mar. 2025, www.fisheries.noaa.gov/feature-story/early-bloom-toxic-algae-southern-california-sickens-hundreds-sea-lions-and-dolphins.
“Can We Clean Up, Stop, or End Harmful Algal Blooms?” National Oceanic and Atmospheric Administration, oceanservice.noaa.gov/facts/hab-solutions.html.
Guest Blogger Tale Chen is a 12th grade student with a passion for science, environmental engineering, and creativity. She leads a sustainability-focused service project that spreads environmental awareness and keeps local waters safe. Her passions for STEM, creativity, and swimming have largely driven her appreciation and love for water. Outside of writing, she enjoys playing water polo and captains her school's national Academic Decathlon team.