marine algal bloom 2010-03-16T12:12:30Z A marine algal bloom is a rapid increase or accumulation in the population of algae in a marine system. Typically, only one or a small number of phytoplankton species are involved. Although there is no officially recognized threshold level, algae can be considered to be blooming at concentrations of hundreds to thousands of cells per milliliter, depending on the severity. ENVO ENVO:01000057 EcoLexicon:red_tide ORCID:0000-0002-4366-3088 red tide algal bloom