The salient criterion to use in defining whether a “harmful”
species is in bloom and the distinctive feature of such
blooms lie not in the level of abundance, but whether its
occurrence has harmful consequences. Harmful bloom occurrences
clearly reveal that pegging the definition of blooms
generally to abundance levels, whether as biomass or numerical
cell abundance, is inappropriate. This is easily
shown. Maximal chlorophyll levels during a brown tide outbreak
of the 2-pm A. anophageflerens in Narragansett Bay
fell within the range of annual winter-spring bloom maxima
(Smayda and Villareal 1989). The significant feature of this
bloom was not its biomass, but its maximal population abundance
which reached 2X lo” cells liter-l.