Phosphorus naturally exists in Lake Champlain and is an essential nutrient for plants, wildlife, and humans to live and grow. Lake Champlain runs into problems when too much phosphorus enters the lake from sources such as:

  • fertilizers from lawns, parks, and golf courses
  • farm runoff - manure & synthetic fertilizers and sediment
  • Eroding river banks
  • loose soil (sediment) in driveways and roads
  • wastewater treatment facility overflows & failures
  • failing & failed septic systems
  • Pet waste
  • human waste dumped from boats
Algae Lake Bloom


Too much phosphorus in Lake Champlain often leads to nuisance plant growth and algae blooms, which are large mats of algae in the water that block sunlight from reaching plants at the lake bottom. As algae within the blooms die, the bacteria that break down the dead algae use up large amounts of oxygen in the water. These low oxygen levels can result in dead fish and other aquatic wildlife.
Some types of algae, such as blue-green algae (cyanobacteria), can produce toxins called cyanotoxins. These toxins have been known to kill fish and dogs, and can make a person ill or worse if swam in or swallowed.