This beautiful chart of Key Players in the Food Web makes clear how each kind of marine life interacts with the others.
It was posted in one of the Forums that accompany this MOOC I'm taking. Highly recommended.
This blog records my experiences as a docent at the Piedras Blancas Elephant Seal Rookery on Highway 1 in California. Adult females and juveniles of both sexes return to the beach in spring to molt.