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The Effects of Runoff Pollution: The Case of Seagrass Meadows

Photo courtesy of Unsplash

As climate change continues to demand attention, the search for possible solutions to regulate the amount of carbon dioxide released into our atmosphere is urgent. Nature provides resources that control the carbon cycle by acting as carbon sinks. Carbon sinks, such as forests, rocks, and oceans, can absorb and store carbon from the atmosphere. Seagrass meadows are vital to carbon sequestration because they store about 10% of the earth’s carbon and they take in carbon 35x faster than rainforests. However, human activities which contribute to agricultural and urban runoff have put these delicate ecosystems at risk.

There are approximately 60 different species of seagrasses, and they can be found across the world’s oceans. Though they resemble seaweed, they’re actually considered angiosperms, and are more closely related to flowering plants. They are great ecosystem indicator species and provide shelter for lots of marine life, but their importance doesn’t stop there. As a carbon sink, they’re able to take up carbon from ocean water through photosynthesis and store it in soil and seabeds for hundreds of years. The lack of oxygen slows down the decomposition process for vegetation, allowing them to behave as a sink for an extended period of time. They also help filter runoff from land and improve water quality, but there is a limit on how much they can handle. Agricultural and urban runoff hinder the growth of seagrass by increasing the nutrient levels in the water, specifically nitrogen levels. A new study shows that 88% of seagrass are exposed to wastewater nitrogen. The nitrogen in pesticides, fertilizers, and wastewater feed phytoplankton, or microalgae, and cause them to bloom rapidly on the surface of water. These algae blooms shade seagrass, depriving them of the sunlight they need to photosynthesize.

Coastal areas with water filtration systems have seen improvement in nitrogen levels. For example, in Boston, Massachusetts, improved sewage treatment plants have led to a significant decrease in nitrogen and a 50% increase in eelgrass from 2006 to 2016. In the South, Tampa Bay saw a 66% decrease in nitrogen since 1970 because of sewage treatment plant upgrades. However, the implementation of these treatment facilities is expensive and it can be difficult to manufacture certain parts for maintenance. Oftentimes facilities are overloaded with wastewater, leading to mechanical issues.

Before any chemicals get a chance to reach treatment plants and our oceans, there are steps we can take to reduce the amount of runoff pollution on an individual level. Some ways you can help reduce runoff pollution include taking proper care of your vehicles. Fixing oil leaks from cars and trucks, and making sure no chemicals are dumped down storm drains are helpful ways to keep harmful fluids out of storm drains. Washing your car at a commercial car wash is better than washing your car at home since commercial car washes typically have drains to trap contaminants. Picking up after pets ensures less waste is washed down storm drains. Additionally, you can avoid using fertilizers and pesticides if possible, and especially avoid using them before a rainstorm.

Human activity has not only increased the amount of carbon being released into the environment, but our individual and collective actions have negatively impacted and damaged the natural sinks that we rely on to balance the earth’s carbon levels. The first step to mitigating this issue is recognizing the ecosystems which are capable of absorbing and storing carbon. The next step is to reevaluate how we live and be mindful of where exactly our waste and chemicals are going when we dispose of them, not only for the benefit of seagrass, but all ecosystems.



Casey, M., & Selsky, A. (n.d.). Scientists struggle to save seagrass from coastal pollution. Retrieved December 4, 2022, from

FORESIGHT Climate & Energy. (2019, March 28). Seagrass beats rainforests as Carbon Sink. Medium. Retrieved December 3, 2022, from

Stormwater runoff pollution and how to reduce it - King County. (n.d.). Retrieved December 4, 2022, from

Wilke, C. (2022, February 24). Analyze this: Nutrients from sewage may harm coastal ecosystems. Science News Explores. Retrieved December 4, 2022, from

What is blue carbon? The Blue Carbon Initiative. (n.d.). Retrieved December 4, 2022, from,of%20carbon%20per%20year)*.


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