Nutrient water pollution causes an overgrowth of algae and microscopic plants, while toxic pollutants in water can put plants under stress or even kill them. Whether the pollution has a positive or negative effect on plant life, it upsets the balance of the ecosystem, often with devastating effects.
Nutrient pollution often occurs because of many human activities, including runoff from farmland. Rain dissolves phosphorous and nitrogen from fertilizers applied to crops and animal waste. The increase in nutrients leads to a potential algae bloom that causes dead spots in the water due to oxygen depletion.
Acid rain is another form of water pollution affecting plant life. Acid rain occurs when water in the atmosphere dissolves chemicals, including sulfur dioxide and nitrogen dioxide, formed by volcanoes and automobile engines. As the precipitation falls to the ground, it pollutes water supplies. It lowers the pH of the water and ultimately the soil, inhibiting the growth of some plants and killing others.
Phytotoxicity occurs when toxins build up in the environment and the plant's root system absorbs them. Chemicals accumulate in water systems and the environment with a cumulative effect. Mercury, which also affects fish and animals, has a toxic effect on plants. Seed fail to grow while mature plants begin to wither and die due to phytotoxicity.