Because green turtles are highly mobile throughout their lives, they are opportunistic feeders.
Because green sea turtles are highly mobile throughout their lives, their food choices are often opportunistic.
As juveniles, green sea turtles will feast on small marine invertebrates and neustonic material like sea serpents (Hydrozoa), moss animals (Bryozoa), and sea hare eggs (Aplysia). They also consume large quantities of wetland plants such as api api (Avicennia schaueriana) and salt-water cord grass (Spartina alterniflora,) which are commonly found in salt marshes.
Mature green turtles are mostly herbivorous and consume large quantities of sea grass and algae. Their diet consists of a variety of red and green algae such as: filamentous red alga (Bostrychia,) red moss (Caloglossa,) freshwater red algae (Compsopogon,) lobster horns (Polysiphonia,) sea lettuce (Ulva lactuca,) green seaweed (Gayralia,) and crinkle grass (Rhizoclonium).