What Causes Algae Blooms?
Algal blooms are an unusually dense growth of aquatic single celled plants (algae). They occur, frequently to the point where they discolor the water, when ideal factors combine to promote growth -- generally light, temperature, salinity and nutrients. Algal blooms are a natural phenomenon but their frequency, duration, extent and density are all increased in waters such as the Chesapeake Bay, where human activities on land increase nutrient runoff.
Large blooms can lead to fish kills by reducing the amount of oxygen in the water. This happens when algae consume all the available oxygen at night, or when the bloom dies and the resulting decomposition of dead algae by bacteria removes oxygen from the water.
Algal blooms can also harm living resources by replacing nutritious algae that fish and shellfish depend on for food with species that the fish cannot survive on. Reducing the amount of nutrient pollution in the Chesapeake Bay is the best action we can take to reduce the occurrence of algal blooms.
- Dave Goshorn, Ph. D., Director
Photo of microcystis in the Sassafras River, September 2000
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