Pseudo-nitzschia australis is a pennate diatom found in temperate and sub-tropic marine waters, such as off the coast of California and Argentina.

This diatom is a Harmful Micro Algae[1] that produces toxic effects on a variety of organisms through its production of domoic acid, a neurotoxin.

[2] Pseudo-nitzschia australis are a part of the genus which are bilaterally symmetrical diatoms with a protective cell wall layer called a silica.

Sexual reproduction has also been found to correlate with higher levels of domoic acid production[5] Population growth of this species is seasonal and can depend on the amount of water upwelled and nutrient concentrations present off of the coast.

[4] These diatoms in a neritic zone meaning that they reside in shallow parts of the ocean with a depth ranging from 0 to 170 meters deep.

Blooms off of the Pacific Coast and Gulf of Mexico have increased in frequency over the 21st century, which scientists speculate may be due to global climate change.

[12] Monterey Bay, located in central California, experienced a toxic P. australis algal bloom in the spring of 2015 leading to detrimental ecological issues such as marine organism illness and mortality.

This bloom was caused by an unusual prolonged period of oceanic warming and upwelling which created conditions that allowed for an explosion of the P. australis species.

The closure of fisheries led to a request from the governor of California for a federal disaster declaration[11] Effects of this harmful algal bloom on wildlife included mortality and seizures of a wide variety of marine species off of the coast.

In the case of DA, glutamate receptors are activated to open ion-gated channels in neurons, which leads to a variety of neurotoxic effects.

[17] At high enough doses, an organism will die of DA poisoning, while sublethal levels may cause a diverse range of effects on the central nervous system.

Experiments showed that mammals exhibit a variety of behavioral and motor impairments, such as seizing, scratching, twitching, yawning, and head-waving.

Domoic acid can accumulate up the food chain and cause adverse effects in marine organisms that are in higher trophic levels.