This type of question can be answered very quickly when you have an understanding of what food chain means. A food chain can be defined as the feeding relationship in which there is a linear network of links in a food web which starts from the producer to the consumers and finally the decomposers. A food chain starts mostly with plants, and they are majorly the producers of the food. They depend mostly on the sun during photosynthesis. The consumers depend on the producers for food.
The decomposers also feed on the consumers, and that is how the cycle continues. From this question, the part that is affected by the sun is the phytoplankton, because it is the producer and producers need sunlight during photosynthesis. The primary consumer here is the zooplankton because it feeds directly on the producer, the secondary consumer is the salmon, and follow by the puffin. So the food chain is; phytoplankton-zooplankton-salmon-puffin
From the food web above, an example of food chain would be phytoplankton-zooplankton- salmon-puffin. Phytoplankton is the producer. Zooplankton is the primary consumer. Salmon is the secondary consumer. Puffin is the tertiary consumer. The producer is the level directly affected by the sun. When one organism is removed from the food web, all other organisms become threatened. For example, if salmon is removed, the puffin and other organisms that rely on salmon will become threatened.
Foodchain: producer: phytoplankton primary consumer: zooplankton secondary consumer: fish - salmon tertiary consumer: gull quaternary consumer: fox
The producer which is the Phytoplankton would be directly affected by the sun. If you would remove one of the one organisms the ecosystem could easily fall apart. For example in my foodchain if you take out the Fox, the number of gulls would increase and the number of salmon would decrease.