Alexandrium

Alexandrium is a genus of microscopic, single-celled algae commonly found in oceans and coastal waters. Some species produce natural toxins that can accumulate in shellfish like clams and mussels, causing a harmful condition known as paralytic shellfish poisoning (PSP) in humans if consumed. These algae sometimes proliferate rapidly during certain environmental conditions, creating large blooms often called "red tides" due to their reddish coloration. While they are part of natural marine ecosystems, their toxins can pose health risks and economic impacts on fisheries and tourism when blooms occur.