How can fertilizer runoff cause algal blooms in lakes and rivers?

Fertilizer runoff contributes to algal blooms through a process known as eutrophication, which occurs when excess nutrients—specifically phosphorus and nitrogen—enter aquatic ecosystems.12

When these nutrients wash into lakes and rivers from agricultural fields, feedlots, or lawn fertilizers, they act as a potent stimulant for algae and other aquatic plants. This influx causes rapid, dense growth known as water blooms. These blooms negatively impact the environment in several ways:1234

• Oxygen Depletion: As the massive amount of algae dies and decomposes, the process consumes vast quantities of dissolved oxygen, leading to hypoxia (low oxygen levels) that can suffocate fish and other aquatic life.124
• Light Blockage: Dense surface blooms prevent sunlight from reaching underwater plants, disrupting the ecosystem's natural balance.24
• Toxicity: Some blooms produce toxins that can poison wildlife and pose health risks to humans.54

Addressing this issue requires responsible pollution control and improved agricultural practices to minimize nutrient runoff and protect the health of our water resources.26