Nutrient overloading is one of the major threats to the lake and the nutrient of concern for Lake Winnipesaukee is phosphorus.

Phosphorus is one of the major nutrients needed for plant and animal growth. It is naturally present in small amounts in freshwater environments, and therefore is considered a limiting nutrient. Just as phosphorus is used to fertilize agricultural land, lawns, and plants, too much phosphorus entering our lake promotes the growth of algae and aquatic vegetation, like milfoil.