Seagrass plants have evolved to grow entirely underwater. Despite their name, these plants are not true grasses; they are just called that because many species have grass-like leaves. Seagrasses help the environment in many ways. The leaves filter water, the roots stabilize sediment, and the plant provides habitat and protection for various fish, shellfish and crustaceans. About 57 seagrass species have been identified.
Shoal grass (Halodule wrightii) is a saltwater seagrass that generally thrives in the shallower, disturbed waters of estuaries, coral reefs and mangrove creeks. Shoal grass grows along the shorelines of North Carolina, the Gulf of Mexico, the Caribbean Islands and Africa. This seagrass has flat, stiff blades that are only about one-tenth of an inch wide and range in length from 1-1/2 to 13 inches.
Widgeon grass (Ruppia maritime) grows in both fresh and salt water and is usually found in bays, estuaries and lagoons. This seagrass features branched or single stems that grow up to 3 feet long. The thread-like leaves grow up to 4 inches in length and are generally very thin (1/32 of an inch). Widgeon grass has stalks that produce fruit clusters and petal-less flowers. Ducks commonly feed on the leaves and stems that stick out above the water. Fish, reptiles and amphibians eat the underwater portions. Widgeon seagrass grows in subtropical and temperate climates, including along the Atlantic coastline. This seagrass often forms large meadows in sub-tidal environments that receive abundant sunlight.
Turtle grass (Thalassia testudinum) is a seagrass common to the Florida and Caribbean shorelines. The ribbon-like, flat leaves reach up to 14 inches in length and are about one-half inch wide. This seagrass grows in shallower waters ranging from the low-tide level to about 30 feet deep. Turtle grass produces greenish-white to pink flowers and round fruit. This grass earned its name because sea turtles like to eat the leaves.
Manatee grass (Syringodium filiforme) is a seagrass with cylindrical leaves that reach up to a foot long and only about a tenth of an inch wide. This seagrass prefers shallow saltwater about 2 to 3 feet deep, but can thrive in water up to 60 feet deep. Manatee grass grows along the eastern coasts of Florida, the Gulf of Mexico, the Bahamas, Bermuda and the Caribbean. Leaves reach up to 20 inches long and is a food source for manatees.
Johnson’s seagrass (Halophila johnsonii) grows in coastal lagoons with shallow waters up to 6 feet deep. This saltwater seagrass is listed as a threatened marine species due to its asexual reproduction and limited distribution. Johnson's seagrass grows along the Florida coastline. This seagrass features elliptical blades typically shorter than 1 inch long and less than one-tenth of an inch wide.
Eelgrass (Zostera marina) grows in the cold saltwater from North Carolina north to Greenland. This seagrass prefers the shallow waters of tidal creeks, estuaries and bays. Eelgrass has round-tipped, ribbon-like blades that reach up to 4 feet long and about one-third of an inch wide. Unlike other types of seagrasses, eelgrass dies back in the summer and thrives in the cooler spring and autumn months.