Phosphorus: Ruins all Fresh Water

Phosphorus: Ruins all Fresh Water

What is Minnesota’s greatest asset? No doubt, it’s the over 10,000 lakes of 10 acres or more. These lakes are valuable for recreation, aesthetic beauty and as a major contributor to Minnesota’s economy. Yet, despite their abundance and value, these lakes face tremendous pressure from increased use, development of their shore lands and their water sheds, the spread of exotic species, and pollution from land run-off and out-of-compliance septic systems. Phosphorus is the primary water pollutant from most of these sources and uses and is, perhaps, the biggest potential threat to clean lakes in Minnesota.

The amount of phosphorus in a lake makes the difference between one that is clean and clear and one that is green and covered with algae. Once phosphorus is in a lake, it is difficult to remove. Phosphorus is called ‘the limiting nutrient’ for algae growth because it only takes a minute amount to significantly increase the growth rate of algae in comparison to other growth substances. It takes only one pound of phosphorus in a lake to produce as much as 500 pounds of algae. The more phosphorus in the water, the more algae grows with decreased water clarity as the result. The algae slowly settle into the deeper water of the lake, where they die and use up oxygen as they decompose. Heavy algae blooms can rob a lake of oxygen needed for the fish and other aquatic organisms to survive and can produce unsuitable conditions for water sports, swimming, and in some cases, can be a health threat to animals and humans.

Phosphorus is a naturally occurring element found as a nutrient in soil and as a component of human and animal waste. It gets into lakes from natural weathering of soils, atmospheric deposition, groundwater recharge of lakes, agricultural runoff from fields and feedlots, pet and waterfowl waste, runoff from lawns, paved areas, and construction sites, shore land erosion and failing septic systems.

Some sources of phosphorus can be controlled with “best management practices (BMPS) to preserve and protect water quality by reducing the amount of phosphorus that eventually reaches the lakes.

If further information is needed, please contact the local University of Minnesota Extension Service at 1-800-525-8636.