Golden Algae

Prymnesium parvum is a species of haptophyte (also collectively called Prymnesiophyta). The species is of concern because of its ability to produce the phycotoxin prymnesin. It is a flagellated alga that is normally found suspended in the water column. It was first identified in North America in 1985, but it is not known if it was introduced artificially (e.g., an invasive species) or missed in previous surveys. Toxin production mainly kills fish and appears to have little effect on cattle or humans. This distinguishes it from a red tide, which is an algal bloom whose toxins lead to harmful effects in people. Although no harmful effects are known, it is recommended not to consume dead or dying fish exposed to a P. parvum bloom.

Prymnesium parvum of Haptophyta is sometimes colloquially misnamed "golden alga" causing confusion with golden alga or Chrysophyceae of Heterokontophyta, leading to contradictions in terms, especially in non-scholarly texts (such as those from state wildlife departments).