Kelp belongs to brown algae, not green algae. Although kelp looks green, it is actually responsible for its chlorophyll. Kelp belongs to the phylum Brown Algae and is a type of brown algae. Unlike green algae, brown algae contain high amounts of lutein and carotene, which give brown algae a yellow or brown hue.
Kelp is an important plant in the ocean, and they usually grow in the intertidal zone and in the deep sea. Kelp has certain requirements for the clarity and temperature of the water quality, so they usually grow better in colder seas. Kelp is found globally, especially in the cold and temperate regions of the Northern Hemisphere.
There are also significant differences in morphology and structure between brown algae and green algae. Chlorella are usually green in color, have thin cell walls, and contain a lot of chlorophyll. Brown algae, on the other hand, are brown or yellow in color, have a thick cell wall, and contain a lot of lutein and carotene. In addition, the morphology of brown algae is also more diverse, including different forms such as filamentous, leafy, cylindrical, etc.
In short, kelp belongs to brown algae rather than green algae, which is determined by its chlorophyll content, morphology, structure, etc.