See text Nitzschia is a common pennate marine diatom.

In the scientific literature, this genus, named after Christian Ludwig Nitzsch, is sometimes referred to incorrectly as Nitzchia, and it has many species described, which all have a similar morphology.

Nitzschia includes several species of diatoms known to produce the neurotoxin known as domoic acid, a toxin responsible for the human illness called amnesic shellfish poisoning.

The species N. frigida is found to grow exponentially even at temperatures between −4 and −6 °C.

[2] Some Nitzschia species are also extremophiles by dint of tolerance to high salinity; for example, some halophilic species of Nitzschia are found in the Makgadikgadi Pans in Botswana.