The specimen of Pseudo-nitzschia is oriented diagonally in the photo.
"In 1991, a relatively new toxin was first detected on the West Coast of the U.S., domoic acid. Domoic acid has been responsible for several deaths and both permanent and transitory illness in over a hundred people. The toxin is produced by marine diatoms which are members of the genus Pseudo-nitzschia.
Both shellfish and fish can accumulate this toxin without apparent ill effects; however, in humans the toxin crosses into the brain and interferes with nerve signal transmission. People poisoned with very high doses of the toxin can die, while lower doses can cause permanent brain damage (short term memory loss).
When this toxin was discovered in certain West coast fish and shellfish, both recreational and commercial fisheries were briefly closed. This closure, though relatively short, had serious economic impacts on those communities dependent on these fisheries."
-excerpt from NOAA Northwest Fisheries Science Center
Image from The Harmful ALGAE Page, National Office for Marine Biotoxins and Harmful Algal Blooms Woods Hole Oceanographic Institution, http://www.redtide.whoi.edu/hab/species/species.html