Non-point sources of pollution are the largest contributor of pollution to Lake Champlain. Non-point source pollution is from widely dispersed sources, such as agricultural fields and urban street run-off. The manure and fertilizer in farm runoff contains phosphorous which contributes to the overloading of nutrients (eutrophication) in certain parts of Lake Champlain. Urban runoff contains nutrients from lawn and garden fertilizers, vehicular pollutants such as gasoline and oil, and pesticides from lawns, gardens, and golf courses.

Phosphorous (P)
Phosphorous is a plant nutrient. High levels of phosphorous can stimulate the growth of algae causing algal blooms. Algal blooms cause the water to turn green, reduce water transparency, deplete the oxygen supply, and create odor problems. Ultimately, these blooms alter fish and wildlife habitat, impair scenic views, reduce recreational appeal, impair water supplies, and lower property values. Algal blooms are a result of eutrophication. Phosphorous contributors include farm and urban runoff, and municipal wastewater treatment plants.

Eutrophication
A body of water can be designated oligotrophic, mesotrophic, and eutrophic depending on the level of phosphorous (P) and the amount of plant growth occurring in a lake or stream. These three conditions occur naturally in water systems, but adding excessive amounts of nutrients to a lake or stream can force it into eutrophication.

Lake water is considered oligotrophic if it is clear and nuisance free with a P level of 10 micrograms/liter. A mesotrophic lake has moderate amount of plant growth and a P level between 10-20 micrograms/liter. A eutrophic lake has excessive plant growth and low water clarity and a P level greater than 20 micrograms/liter.

Zebra mussels and other exotics
The introduction of exotic species (non-natives), such as zebra muscles and purple loosestrife, can be a threat to the native species of Vermont. Exotic species have no natural predators and thereby flourish and out-compete native plants and animals. Exotics are introduced inadvertently by boats, ornamental vegetation that escapes, and as introduced game species. For more information visit the Vermont Agency of Natural Resource's Non-native Plant and Animal Species of Concern web site.

About water pollutants
Water pollutants can be sediments, nutrients, bacteria, and toxic substances. Pollution sources include the atmosphere, urban and farm runoff, recreational and commercial boating, water treatment facilities, and industrial by-products. Water quality concerns that stem from these pollutants include bacterial contamination, nutrient enrichment, contaminated fish, exotic species, and the loss of wetlands. Boaters, anglers, swimmers, lakeshore homeowners, and water managers are all concerned about the water quality in the Burlington area