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The Effect of Phosphates on Aquatic Plants

By Joan Norton ; Updated September 21, 2017
Ponds can be polluted by excessive phosphates in the water.
by the pond image by Quennie Chua from Fotolia.com

Phosphorus is often added to soil in fertilizer to increase crop production. It is the macronutrient “P” on fertilizer NPK labels. Overuse use of synthetic fertilizer has caused excessive amounts of phosphorus from agricultural areas to flow into waterways. The increase in phosphate content in water leads to distortion in aquatic plant growth cycles, such as the development of algae blooms and overgrowth of water weeds.


Excess phosphates in water over-fertilize aquatic plants and increase the eutrophication process. Eutrophication is the natural aging process of a body of water which takes thousands of years. “Cultural eutrophication,” according to Wilkes University Center for Environmental Quality, “is an unnatural speeding up of this process because of man’s addition of phosphates, nitrogen and sediment to the water.” Bodies of water are being aged faster than nature creates them.

Excess Phosphate

In some agricultural areas fertilizer run-off accounts for a high percentage of the excess phosphate in water. The Kansas Water Science Center reports that 65 percent of the phosphorus transportation into the Cheney watershed results from agricultural activity.Phosphorus degrades the quality of public drinking water as well as over stimulating algae production in recreational water areas.

Algae Growth

Excess phosphorus stimulates water weeds and algae growth, which chokes oxygen from other aquatic plants. Over-stimulated weeds grow and die more quickly than is natural, using up the available oxygen. Algae increases in water that contains excessive phosphorus, resulting in “algae blooms.” An algae bloom produces toxins that cause illness or death in pets, livestock and humans, according to the Ohio Environmental Protection Agency.

Eutrophic Lakes

Phosphorus stimulation in lakes results in a nutrient-high environment that produces massive weed growth as well as potential algae bloom. The lake may support a large fish population but is susceptible to oxygen depletion. Small, shallow lakes with excess phosphorus are subject to winterkill, which reduces the number and variety of fish. Fish not used for food or sport are commonly found in lakes that are phosphorus polluted.


Phosphorus pollution to aquatic plants and fish is the result of human activity and as such, can be reduced. The United States Environmental Protection Agency works with states to identify waters with phosphorus overload and establish maximum daily levels of phosphorus and other harmful substances. Home gardeners can participate in a local Adopt-Your-Watershed program and volunteer to help protect water from phosphorus overload and other forms of pollution problems.


About the Author


Joan Norton, M.A., is a licensed psychotherapist and professional writer in the field of women's spirituality. She blogs and has two published books on the subject of Mary Magdalene: "14 Steps To Awaken The Sacred Feminine: Women in the Circle of Mary Magdalene" and "The Mary Magdalene Within."