The chemical can bioaccumulate in marine organisms that feed on the phytoplankton, such as shellfish, anchovies, and sardines. The toxin does not bioaccumulate in the classic sense because it is quickly excreted by fish and shellfish that ingest it. It only accumulates in high numbers in these plankton feeders when the diatom itself is high in number in the surrounding waters. Bioaccumulation or biomagnification typically occurs in lipid-rich tissues, which accumulate toxins over time. In classic bioaccumulation, the older and larger an organism is, the longer it has to accumulate the toxins in its fats, and therefore, the higher the concentration of toxin.
In mammals, including humans, domoic acid acts as a neurotoxin, causing short-term memory loss, brain damage and, in severe cases, death. Algal bloom are associated with the phenomenon of Amnesic shellfish poisoning (ASP). In marine mammals, domoic acid typically causes seizures and tremors. In the brain, domoic acid especially damages the hippocampus and amygdaloid nucleus. It damages the neurons by activating AMPA and kainate receptors, causing an influx of calcium. Although calcium flowing into cells is a normal event, the uncontrolled increase of calcium causes the cell to degenerate. Because the hippocampus may be severely damaged, long-term memory loss occurs.