While small amounts of nutrients are vital to all life, excessive amounts can be damaging. Forests contribute lower amounts of nitrogen and phosphorous to waterways than do other land uses. The primary nutrients polluting the Chesapeake Bay are nitrogen and phosphorous. High amounts of these nutrients increase the growth of algae. Algae becomes so abundant that the color of the water turns brownish or greenish.
Sunlight is blocked from reaching other plants.
When the algae die and decompose, oxygen dissolved in the water is used. Often, so much oxygen is used by decomposing algae that fish and other animals must move to areas with more oxygen. Plants and animals that cannot move may die. This reduction would significantly increase the amount of dissolved oxygen in the Bay improving conditions for plants and animals. In the late 1980's, progress was made by controlling the amount of phosphorous, especially from wastewater treatment plants.