Chemical Runoff: What It’s Doing to Our Waters
Chemical runoff from farms, cities, and industry is polluting our waters, harming coral reefs and marine life. Learn how these pollutants spread and what we can do to reduce their impact.
PRESERVING OUR GREAT LAKES AND OCEANS
Chemical Runoff: What It’s Doing to Our Waters
What Is Chemical Runoff?
Chemical runoff refers to the substances—like fertilizers, pesticides, industrial waste, and sewage—that wash from land into rivers and coastal waters. This runoff carries nitrogen and phosphorus from agriculture, toxic herbicides and heavy metals from farms and factories, and untreated wastewater from households and septic systems.
These pollutants trigger algal blooms, oxygen depletion, and chemical poisoning that change entire ecosystems.
Nutrient Pollution & Eutrophication
Excess nitrogen and phosphates fuel harmful algal blooms, which block sunlight and consume oxygen as they break down—a process known as eutrophication. The result? Dead zones where fish and coral can’t survive, reef smothering, and shifts in marine communities.
Studies show nutrient overload slows coral growth by more than 50 percent and accelerates disease, such as yellow band and fungal infections.
Toxic Chemicals & Pesticides
Herbicides and pesticides are especially harmful in reef areas. Some have been detected in coral tissues, reducing photosynthetic capacity and reproduction while increasing bleaching and mortality.
Heavy metals like copper, mercury, and lead also accumulate in coral and fish, interfering with growth, development, and reproductive health even at very low levels.
Wastewater & Sewage Impacts
Up to 80 percent of global wastewater enters waterways untreated, introducing a mixture of nutrients, pathogens, pharmaceutical residues, microplastics, and industrial chemicals. These combine to weaken coral resilience and increase disease risk.
Sewage also contributes to chemical pollution and algal overgrowth, further stressing coral communities already weakened by climate stressors.
Ocean Acidification & Ecosystem Disruption
When algal blooms die and decompose, bacteria consume oxygen and release carbon dioxide into the water, increasing local ocean acidity. This affects calcifying organisms such as corals and shellfish, preventing healthy skeletal growth and reproduction.
Chemical pollutants like fungicides and herbicides further degrade reef health and disrupt the natural pH-regulating processes of marine ecosystems.
What Divers and Communities Can Do
Support buffer zones and wetlands around farms to absorb excess nutrients.
Advocate for improved wastewater treatment and limits on industrial discharge.
Use biodegradable cleaning products and organic fertilizers at home.
Get involved in local water-quality monitoring or restoration initiatives.
Share knowledge about runoff impacts with fellow divers, beachgoers, and policy makers.
Happy and safe diving,
The ScubaBlast Team
References:
Environmental Literacy Council. (n.d.). How do pollution and runoff affect coral reefs? Retrieved from https://enviroliteracy.org/what-human-activities-affect-coral
Environmental Literacy Council. (n.d.). Nutrient pollution: causes and effects. Retrieved from https://enviroliteracy.org/how-does-pollution-affect-coral-reefs
Nova Science Publishers. (2016). Nutrient pollution from agricultural production: Overview and management.
Coral Reef Alliance. (2025). Major water-quality issues plaguing coral reefs today. Retrieved from https://coral.org/en/blog/major-water-quality-issues-plaguing-coral-reefs-today/
University of Exeter & Southampton Research. (n.d.). Study linking fertilizer runoff to coral decline. Retrieved from https://realnatural.org/dying-of-coral-reefs-linked-to-conventional-fertilizers/
Marine Biodiversity Science Center. (2025, April). Ocean acidification’s chemical chain reaction: How runoff threatens marine life. Retrieved from https://www.marinebiodiversity.ca/2025/04/ocean-acidifications-chemical-chain-reaction-how-runoff-threatens-marine-life/
EPA. (2024, January). Latest assessment shows no improvement in U.S. nutrient pollution. Retrieved from https://apnews.com/article/571eb54cb69cc06f43d5f1253e990337
Reuters. (2025, May). Divers cleaning seabed off Greece raise alarm over marine pollution. Retrieved from https://www.reuters.com/sustainability/climate-energy/divers-cleaning-up-seabed-off-greeces-alonissos-raise-alarm-over-marine-2025-05-27