Algal bloom

Posted: 21 August 2000

Abnormally increased biomass of algae in a lake or river. Algal blooms occur naturally in spring and early summer, when the rate of reproduction of the algae outstrips that of their consumers. However, the most serious algal blooms are associated with human activities. Phosphates and nitrates carried into waterways in sewage, agricultural fertilisers and detergents, provide the nutrients that cause explosive growth in the algae population.