Seagrasses

 

Description: Seagrasses are underwater plants that evolved from land plants. They are like terrestrial plants in having leaves, flowers, seeds, roots, connective tissues and in making their food through photosynthesis. Unlike terrestrial plants they do not have strong stems to hold them up, but instead are supported by the buoyancy of the water that surrounds them. Seagrasses are very important food source and habitat for wildlife, supporting a diverse community of organisms, including many fish, octopus, sea turtles, shrimp, blue crabs, oysters, sea turtles, sponges, sea urchins, anemones, clams and squid. Seagrasses have been called “the lungs of the sea” as they release oxygen into the water through the process of photosynthesis. They provide a nursery area for many fish and invertebrates, including commercially important fish species, as the grasses provide concealment and help to lessen the effects of strong currents and their leaves provide a place for the attachment of eggs and larvae. Their leaves and stems provide food for herbivores like sea turtles and manatees. Plankton, algae and bacteria grow on seagrass stems, providing food for additional organisms. Dead seagrass provide food for decomposers like worms, sea cucumbers, crabs and filter feeders. Seagrasses improve water quality by trapping sediments, absorbing nutrients and stabilizing sediment with their roots.

Habitat: Shallow, soft-bottomed, sheltered coastal waters, both tropical and temperate.

Range: There are 26 species of seagrasses in North American coastal waters.

Life History and Reproduction: Seagrasses can reproduce sexually or asexually. They are flowering plants that produce seeds. Pollen is carried through the water to fertilize female flowers. Seagrasses can also send out rhizome roots that can sprout new growth, so a single plant is capable of producing an entire underwater meadow.

Fun Fact: Seagrasses are not true grasses. They are more closely related to terrestrial lilies and gingers than grasses.

Conservation Status: Seagrasses are very sensitive to water quality and are an indicator of the overall health of coastal ecosystems. Since they produce energy through photosynthesis they do best where the water is clear enough to allow sunlight to penetrate. Pollution, sedimentation, excessive nutrients, storms, disease, and overgrazing by herbivores are all pose threats to seagrasses.

Videos:

Pastures of the Sea
Seagrass and Seagrass Beds, Smithsonian Ocean Portal

Additional Resources:

The Secret Garden: the Hidden World of Seagrasses, National Park Service WebRangers

Sources:

Florida Keys National Marine Sanctuary
Importance of Seagrass, Florida Fish and Wildlife Conservation Commission
Seagrass and Seagrass Beds, Smithsonian Ocean Portal
Seagrass Habitats, Smithsonian Marine Station at Fort Pierce
Seagrasses of North America, Seagrass Recovery
What is Seagrass?, Seagrass Watch

 

 

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