Florida seaweed | Florida Department of Environmental Protection

Florida seaweed |  Florida Department of Environmental Protection

Seaweeds are grass-like flowering plants that live completely submerged in marine and estuarine waters. Although seagrasses are found throughout coastal areas of Florida, they are most abundant in Florida Bay and from Tarpon Springs north to Appalachian Bay in the Gulf of Mexico, two of the most widespread seagrass beds in continental North America.

Seagrasses are found in protected bays and lagoons and also in deeper waters along the continental shelf in the Gulf of Mexico. The depth at which seaweed is found is limited by the clarity of the water because most species require high levels of light.

Florida’s approximately 2.2 million acres of seagrass perform several important functions:

  • Maintains water purity by trapping sediments and fine particles with its leaves.
  • Secure the bottom with roots and rhizomes.
  • Provide shelter for fish, crustaceans and shellfish.
  • In addition to the organisms that grow on it, it provides food for many marine animals and waterbirds.

The seagrass canopy protects small marine animals, including juvenile species such as drum, sea bass, snapper, and grunts, from larger predators. Some animals, such as manatees, urchins, oysters, and sea turtles, eat seagrass blades. Other animals derive their food from eating algae and small animals that live on seaweed leaves. Bottlenose dolphins and a variety of wading and diving birds also use seagrass beds as feeding grounds. Seaweed detritus, which consists of microbial decomposition of leaves and roots, is also an important food source.

Florida seaweed

Although there are approximately 52 species of seaweed found worldwide, only seven species are found in Florida’s marine waters. Six of them are widespread in Florida and extend beyond its borders.

The tortoise grass (Thalassia testudinum) meadow of St. Martins Marsh provides food and cover for countless wildlife.

Turtle grass (Thalassia turtles), the largest seaweed in Florida, has a deeper root structure than any of the other seaweeds. It has large, ribbon-like leaves that range from 4 to 12 mm wide and 10 to 35 mm long. This seagrass is thermolimited and is not found along the northeastern coast of Florida, but it forms extensive beds in Florida Bay.


Gasparilla Sound-Charlotte Harbor Aquatic Reserve-Shallow Grass

Shallow grass (Halodol rayiti) is an early colonizer of vegetated areas and usually grows in water that is too shallow for other species except wedge grass. It is most common in inlets along the East Coast.


Manatee grass (Syringodium filiforme)

Manatee grass (Filamentous syringomyelia) It is easily recognizable because its leaves are cylindrical rather than ribbon-shaped and flat like many other seaweed species. Thin leaves reach half a meter in length. The northern limit of the manatee grassland is the Indian River near Cape Canaveral. Manatee grass is usually found in mixed seagrass beds or in small, dense, single-species patches.


Weed weed (Marine rupee) grows in both fresh and salt water and is widely distributed throughout Florida’s estuaries in less saline areas, especially in bays along the east coast of Florida.


Star grass (Halophila Engelmannii)

Three types of Halophila Found in Florida – star grass (Halophila engelmannii), grass paddle (Halophila is deceptive) and Johnson’s seaweed (Halophila johnsonii). These are smaller, more fragile seaweeds. There is only limited information about them, although surveys are underway to determine their ecological roles. Johnson’s seaweed grows only in the Indian River Lagoon south of Biscayne Bay and is listed as a federally threatened species.

Johnson's seaweed (Halophila johnsonii)

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