Algae form the base of the aquatic food web, given their significant contribution to global photosynthesis. Algae are plant‐like life forms that float or move on their own in water. They vary in size from very small (microalgae; i.e., phytoplankton) to very large (macroalgae; e.g., seaweed). This article focuses on microalgae and the small percentage that may be harmful. A rapid increase in the population of algae, called an algal bloom, can deplete oxygen in the water column, creating hypoxic or anoxic conditions. These conditions can lead to changes in food web dynamics and, therefore, changes in the species of marine life present; reduce light penetration through the water column; and cause fish kills, generally by the clogging of the gills.
A subset of these harmful microalgae is known as toxic algae. The toxins (poisons) produced by toxic algae in the marine environment are referred to as marine biotoxins; however, biotoxins may also be produced by certain freshwater algae and cyanobacteria. This article focuses on the toxins in the marine environment that may accumulate in molluscan shellfish such as oysters, clams, and mussels. If shellfish contaminated with these toxins are consumed, the toxins can sicken, or in extreme cases prove fatal, to the people who eat them.1 Given the potential adverse effects on human health, it is critical to ensure the appropriate control and management of marine biotoxins to prevent contaminated product from entering interstate commerce.