Which marine reptile is the only sea turtle that regularly eats seagrass and algae as an adult?

The green sea turtle is the marine reptile whose adults regularly graze on seagrass and algae.

Green sea turtles are omnivorous when young, eating animal prey as well as plants. As they mature, many shift toward a largely herbivorous diet of seagrasses and algae. This feeding pattern gives them an important ecological role: grazing can maintain the productivity and structure of seagrass meadows.

The species lives in tropical and subtropical oceans, migrating between feeding grounds and nesting beaches. Females return to land to lay eggs, often showing strong fidelity to the region where they hatched. Hatchlings begin life in the open ocean before moving into coastal habitats as they grow.

Their common name does not describe a green shell. It refers to the greenish colour of their body fat, caused partly by pigments in their plant-rich diet. Green sea turtles remain threatened by habitat loss, fisheries bycatch, illegal harvest, pollution and climate-related changes to nesting beaches.