algal bloom

algal bloom The dense spread of algae which results from changes in the chemistry and/or temperature of lake water. Blooms may be green or red, and are most common in spring or early summer, when primary production outstrips the growth of the consumer organisms. The addition of phosphorus as a result of pollution from fertilizers is an important factor in the growth of algal blooms. The bloom will disappear if the input of fresh phosphorus ceases. See eutrophication.