Alexandrium tamarense (L. Fritz)

Pseudo-nitzschia australis (J. Rines)

Chaetoceros (R. Horner)


One major group of aquatic microorganisms inludes photosynthetic algae and cyanobacteria, as well as non-photosynthetic protists.  Some of these organisms cause problems when they accumulate in sufficient numbers due to their production of endogenous toxins, their sheer biomass, or even their physical structure.  These are the HAB species.

Only a few dozen of the many thousands of species of microscopic and macroscopic algae are repeatedly associated with toxic or harmful blooms. Some species, such as the dinoflagellate Alexandrium fundyense and the diatom Pseudo-nitzschia australis, produce potent toxins which are liberated when the algae are eaten.

Other species kill without toxins, like the Chaetoceros species which has spines with serrated edges, which can lodge in fish gill tissues, causing irritation, over production of mucous, and eventual death. Each of these harmful species need careful study at the organismal level if we are to understand the population dynamics and trophic impacts of HABs throughout the U.S.

Last updated: July 28, 2016