How can fertilizer runoff disrupt an inland water food web?

Fertilizer runoff disrupts inland water food webs primarily through a process called eutrophication. When excess nutrients—specifically nitrogen and phosphorus—enter lakes and rivers, they trigger the explosive growth of algae and other microscopic organisms, resulting in water blooms.123

This disruption impacts the food web in several ways:

• Oxygen Depletion: As these massive algal populations die and decompose, the process consumes vast amounts of dissolved oxygen. This leads to hypoxia, which can cause massive fish kills and suffocate other aquatic animals.234
• Light Blockage: Dense blooms form a mat on the water's surface, preventing sunlight from reaching submerged plants and photosynthetic organisms, which are essential components of the ecosystem.25
• Physical Interference: Thick blooms can clog the gills of fish, further contributing to mortality.5
• Toxin Production: Some blooms produce harmful toxins that can sicken or kill birds, mammals, and aquatic life, while rendering shellfish unsafe.56

Ultimately, this pollution simplifies the food web by favoring small, rapidly reproducing organisms while eliminating larger, more complex species, leading to overall ecosystem degradation.24