|1. Algae are a diverse group of photosynthetic organisms that occur in all marine and freshwater habitats, where they are the base of the food chain, providing both carbohydrates and oxygen.
2. Cultures throughout the world have used various algae as food for humans and livestock and for a variety of other economically important products.
3. The harmful effects of algae are largely due to the production of toxins by various species under bloom conditions.