Why is there green slime on ponds?

Green slime on ponds is typically caused by an overgrowth of algae, often due to excess nutrients like nitrogen and phosphorus from fertilizers, runoff, or wastewater. This phenomenon, known as algal bloom, can thrive in warm, sunny conditions, leading to the rapid multiplication of algae. While some algae are harmless, excessive blooms can deplete oxygen in the water, harming aquatic life and disrupting the ecosystem.