The food web in the image begins with the kelp, which is a producer. Producers are organisms that can make their own food, usually through photosynthesis. Kelp is a type of seaweed that uses sunlight to produce energy.
The sun is not directly part of the food web but it is the source of all the energy in the ecosystem. The kelp captures this energy from the sun and stores it in organic molecules through photosynthesis. These organic molecules are then used by the kelp to grow and reproduce.
Consumers in the food web then eat the producers and transfer this energy up the food chain. For example, the sea urchins in the image are primary consumers that eat the kelp. They are the first level in the food chain after producers.
Not all the arrows in the food web are shown but we can infer some of the missing relationships. For example, the mussels and barnacles are likely filter feeders that feed on plankton, which is not shown in the image. Plankton are microscopic organisms that drift in the water column and can be producers or consumers. The coastal fish are likely omnivores that feed on a variety of things including plankton, mussels, barnacles, and kelp.
Rephrase this sentence into a 9th grader