[1] Some species are capable of producing the neurotoxin domoic acid (DA), which is responsible for the neurological disorder in humans known as amnesic shellfish poisoning (ASP).

It was originally hypothesized that only dinoflagellates could produce harmful algal toxins, but a deadly bloom of Pseudo-nitzschia occurred in 1987 in the bays of Prince Edward Island, Canada, and led to an outbreak of ASP.

This anomaly is likely due to increased awareness of harmful algal blooms (HABs) and their implications for human and ecosystem health.

[4] Blooms have since been characterized in coastal waters and the open-ocean worldwide and have been linked to increasing marine nutrient concentrations, warming ocean temperatures, and bacterial interactions.

The silica frustules also contribute vastly to the sediment layers of the earth and to the fossil record, which makes them exceptionally useful in increasing understanding of numerous processes such as gauging the degree of climate change.

[6] Until 1994, the genus was known as Nitzschia, but was changed to Pseudo-nitzschia because of the ability to form chains of overlapping cells, as well as other minor morphological differences.

[8] While the genus can be readily recognized using light microscopy, identification of distinct species can require taxonomic expertise and be extremely time-consuming.

Optical microscopy identification techniques are inadequate when a large number of samples must be routinely examined, such as is required for a monitoring program for public health.

[11] The physiological distribution, fixation, and recycling center for inorganic carbon and nitrogen plays a key role in the metabolic response of diatoms to prolonged nutrient deprivation.

The cycle enables diatoms to respond immediately to the availability of nutrients and recover by increasing their metabolic and growth rates.

[19] Various species have been detected in the open ocean as well as gulfs and bays, showing a presence in many diverse environments, including off the coasts of Canada, Portugal, France, Italy, Croatia, Greece, Ireland, Australia, Morocco, Japan, Spain, Tunisia, Namibia, Singapore, Angola, Philippines, Turkey, Ukraine, Argentina, and Uruguay.

[20][4] Given the warming temperatures of ocean water, decreasing sea ice, and increasing light penetration brought on by climate change, it is likely that the season for favorable growth of toxigenic Pseudo-nitzschia species will expand.

[4] It is important to continue monitoring Pseudo-nitzschia blooms and their toxicity, particularly in Arctic and Antarctic habitats that may begin to see higher prevalence of these species.

This bloom was dominated by P. australis and likely caused by anomalous warm water and nutrients brought to the surface by upwelling conditions.

[5] Shellfish become contaminated after feeding on toxic Pseudo-nitzschia blooms and can act as a vector to transfer domoic acid to humans upon ingestion.

Effects can be as minor as vomiting, cramps, and a headache, or as severe as permanent anterograde memory loss, coma, and death.

[22] So, monitoring systems and management practices for recreational and commercial fishing are important to ensure the health of marine animals and their predators.

[21] Many factors have been linked to promotion of DA production, including sufficient light, elevated or decreased pH, and nutrition limitations.

However, toxin production increases when the nitrogen source could not sustain a high biomass, suggesting growth limitation seems to induce toxicity.

[24] Pseudo-nitzschia species also appear to respond dramatically to differences in trace metal concentrations, such as iron (Fe) and copper (Cu).