The loggerhead turtles have powerful jaws enabling them to crush even the hard-shelled prey like sea urchins and whelks. They are mostly carnivores but they eat vegetation as well. Generally, the diet of the adult loggerheads consists of fish, jellyfish, sea anemones, sea cucumbers, sea stars, sea pens, bristle worms, clams, sea cookies, cephalopods, man-of-war, horseshoe crabs, mussels, conchs, barnacles, corals, algae, isopods, higher or vascular plants and other bottom-dwelling invertebrates.
The rare diet of these turtles is sargassum and seaweed. As the loggerheads migrate to open seas, they prefer feeding on floating egg clusters and mollusks, flying fish, jellyfishes, pteropods and squids.
The diet of the hatchlings, however, consists of sargassum weed, gastropods, sponges, crustaceans and jellyfish.
Sources:
“Loggerhead Sea Turtles, Caretta caretta ~ MarineBio.org.” MarineBio Conservation Society. Web. Accessed Tuesday, October 24, 2017.
“Information about Sea Turtles”. Sea Turtle Conservancy
“Caretta caretta”. Encyclopedia of Life