home nav buttonphytoplankton nav buttonglossary nav button
left arrow right arrow


pseudo bloom


Genus: Pseudo-nitzschia | Diatom


Common West Coast species: P. australis, P. multiseries, P. pungens, P. fraudulenta, P. pseudodelicatissima

Order: Bacillariales




Click on illustration to enlarge


Description: Cells are elongate, fusiform or rectangular in girdle view. Form chains by overlapping cell ends. Chains of 20 or more cells are not uncommon.

Cell Size: Width 2-8um, Length 40-175um

Distribution: Widespread

Interesting Facts: Many species produce domoic acid, a neurotoxin which is responsible for Amnesiac Shellfish Poisoning. In Monterey Bay, well-known toxin producers P. australis and P. multiseries often form dense blooms.

Bait fish, such as anchovies and sardines, may feed on these blooms and subsequently transfer the domoic acid to their predators which include seabirds and marine mammals. The toxin has a deleterious effect on these animals, often resulting in their deaths.  Interestingly, the species of Pseudo-nitzchia capable of producing domoic acid do not do so all the time.  The conditions that trigger toxin production are of great interest to researchers. 

IFCB images

This Phytoplankton Identification page is affiliated with CeNCOOS and HABMAP, and is maintained by the Kudela Lab at the University of California Santa Cruz. Details about site history, funding, and sources of information and images can be found here.