Seagrass beds are important feeding grounds for thousands of species around the world, and they support this diverse food web in three different ways. Some organisms eat the living leaves directly, such as the ecosystem’s large grazers, including manatees and green sea turtles (Chelonia mydas). Many of these large grazers are now endangered, in large part because of habitat destruction, but once they were very common. It's estimated that before Europeans settled America in the 1400's, the number of green turtles supported by seagrass meadows was 15 to 20 times the number and biomass of large hooved animals in the Serengeti Desert alive today!
Seagrass beds support far more than grazers, however. When the leaves die, they decay on the ground below, supporting organisms that thrive on rotting material. And, lastly, some of these living and dead seagrass blades are washed away to other areas of the ocean, feeding organisms in ecosystems as far as the deep sea.
The collection of smaller animals hiding amongst the seagrass blades and feeding on decaying seagrass attracts bigger animals, accumulating thousands of species in this single habitat. The ecosystem may be home to many types of fish, octopuses, squids, cuttlefish, snails, oysters, sponges, shrimps, sea fleas, worms, urchins, anemones, microalgae, crabs, polychaetes, clams, diatoms, dinoflagellates, copepods—the list goes on. Some of these organisms are permanent residents, while others just pass through.