Seaweeds are large benthic algae. They are the main producers of coastal waters. According to the characteristics of pigment types, storage materials and life history in algae, they can be divided into three categories: green algae, brown algae, and red algae. Because light is needed for photosynthesis, it is usually distributed in the intertidal and sub-tidal zones where the light can reach, and it is one of the main producers in the marine coastal environment.