Why is the runoff from fertilized agricultural fields, even if free of pesticides, often harmful to the ecosystems of temperate lakes?
◦ Runoff water pools at the lake's bottom, where the fertilizer compounds react with materials in the sediment to form toxic substances.
◦ The runoff is acid, and acidification kills key lake organisms.
◦ Fertilizer compounds create large hydrothermal vent communities that kill lake organisms.
◦ The runoff causes heavy growth of algae, which eventually die and decompose, causing oxygen depletion.