The plant kingdom is made up of multi-cellular, photosynthetic Eukaryotas. These multi-cellular organisms contain specialized cells that perform different tasks. Algae are some of the simplest aquatic plants, often referred to as seaweed in the marine environment.
Marine algae are abundant throughout the ocean and can either float freely or cling to substrate such as rocks and reefs. The majority of seaweeds are classified as red algae (6000 species). There are also brown algae (2000 species) and green algae(1200 species). None of the algae species are known to be poisonous, and many species are harvested for human consumption.