A population....... I think
Autotrophs are the producers in the food chain, meaning they create their own nutrients and energy. Kelp, like most autotrophs, creates energy through a process called photosynthesis. An autotroph is an organism that can produce its own food using light, water, carbon dioxide, or other chemicals
Did you mean photoautothrops, if so, the answer is photosynthesis, please tell me if this helped.
