What is a potential environmental impact of excess algae growth in ponds?

Excess algae growth, often referred to as algal blooms, can lead to significant harm to aquatic life in ponds. When algae proliferate excessively, they can consume large amounts of oxygen in the water, especially when they die and decompose. This process, known as eutrophication, can result in hypoxic or anoxic conditions, where oxygen levels drop significantly. Many aquatic organisms, including fish and invertebrates, require oxygen to survive, and a depletion of this essential resource can lead to fish kills and a decline in the overall health of the ecosystem.

Additionally, some algal blooms can produce toxins that are harmful not just to aquatic life but also to animals and humans that may come into contact with or ingest the contaminated water. The detrimental effects on biodiversity and the disruption of food chains are critical concerns associated with excess algae growth. Therefore, the option highlighting harm to aquatic life accurately reflects a significant environmental impact arising from excess algae in ponds.