Phosphorus is a nutrient that is needed by most living organisms and is important to plant growth. It is considered a limiting nutrient because all other nutritional factors that make plants grow (sunlight, water, nitrogen) are available in abundance except for phosphorus. Typically, plants get just enough from natural sources. If too much phosphorus is allowed to enter a body of water, it can create an over-bloom of algae and be very damaging to the ecosystem.
While phosphorus can come from natural sources such as aquatic bird waste and plant decomposition, human activity has been known to create excess phosphorus in a body of water. Fertilizers, detergents, sewage, pet waste and agricultural runoff can make their way to the water directly or by snow melt or stormwater runoff. If vegetation around ponds and lakes have been removed, or if there is shoreline erosion or stream channel modification, it makes it easier for pollution including phosphorus, to enter the water body.
Since phosphorus is a limiting nutrient and only so much is available at certain times, even a small increase of phosphorus levels can increase algae growth and can also create cyanobacteria. Cyanobacteria are photosynthetic bacterial blooms that form on water, creating a greenish blue scum that can be toxic and cause illness to humans and animals.
As algae cells begin to die, they settle at the bottom of the water body and begin to decompose. This depletes the amount of dissolved oxygen in the water and releases even more phosphorus, which continues the algae bloom cycle. The reduction of dissolved oxygen can be detrimental to fish, plants and other living organisms in the water. Some bodies of water with an infiltration of phosphorus will look like pea soup because of all the algae blooms.
Phosphorus can be hard to remove, so it is best to keep it from entering the water to begin with. Some ways to avoid excess phosphorus from getting into the groundwater, which can then make its way to a body of water, is to maintain your septic system by having it pumped regularly, use only phosphate free detergents and soaps in or around your home. Avoid using fertilizers and if you do, do not dump grass clippings or leaves into wetlands or ponds. It’s also important while enjoying outdoor activities such as fishing, boating or camping not to use a lake or pond as a bathroom and do not allow your pets to do so either.
There are products that can be used and ways to reverse the effects of phosphorous such as aluminum salts (alum) and pond aeration. There is also a product on the market called “Phoslock” which is a lanthanum modified bentonite clay that will bond with phosphorus and absorb the molecules. Using these types of products can help, but may need to be done in phases and the water quality must be put into consideration. If you have questions about mitigating a body of water for phosphorus, it is recommended to contact your state’s Department of Environmental Services or a lake and pond management company.
