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There are many imminent threats to Maine lakes. Near the top of the list, and perhaps the most pervasive, is the potential for lakes to become nutrient enriched and more biologically productive as a result of development in lake watersheds. This condition is characterized by declining water clarity (transparency), resulting from an increase in the growth of algae. Excess algae in lake water can cause a disturbance to the normal equilibrium of the aquatic ecosystem. As algae die and decompose, bacteria consume oxygen that is dissolved in the water. Increased algal growth can lead to a decline in oxygen levels, especially during the warm summer months. Oxygen loss can reduce critical habitat for coldwater fish (trout and salmon), and it can accelerate the decline of water quality.

The enrichment of lakes with the nutrient phosphorus and excess algae, resulting from watershed development, is referred to as “cultural eutrophication” (CE). Stormwater runoff from disturbed or developed areas of lake watersheds typically carry high concentrations of phosphorus, sediment particles, and other pollutants considerable distances, eventually flowing into a lake. Lake watershed boundaries may be situated close to the shoreline, or they may extend for miles away from the lake. In either case, stormwater runoff from developed areas of lake watersheds is a potential threat to water quality, unless conservation practices are in place to control stormwater runoff.


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