Seagrass meadows are among the most diverse of all marine communities.

Seagrass beds are an important ecological component on nearshore marine environments and they occur in all coastal areas of the world except in Antarctica. They are highly productive, provide nursery habitat for rearing and sheltering small fishes and invertebrates, and provide food for a wide variety of animals and create habitat and substrate diversity.

Biscayne National Park contains many seagrass beds. Approximately 70 percent of the Biscayne’s recreationally and commercially important fishes, crustaceans, and shellfish spend a portion of their lives in the bay’s environment. There are four major types of seagrasses found in the bay.

Shoalgrass, Halodule wrightii, is an early colonizer of disturbed areas and usually grows in very shallow water.

Turtle-grass, Thalassia testudinum, is the most common seagrass in the park. It has wide leaf blades and a deep root structure, and forms most of the large, lush seagrass meadows found in the park.

Manatee grass, Syringodium filiforme, is recognized easily because of its cylindrical leaves. Halophila species have small, paddle-shaped leaves in pairs or clumps and have lower light requirements than other species.

The following marine plants have been documented in Biscayne National Park. They are listed alphabetically by common name. The list is not exhaustive, and documented sightings of species not on this list are welcome. Submit your sightings to the webmaster.

Halophila englemanni
Johnson’s seagrass, Halophila johnsonni
Manatee grass, Syringodium filiforme
Paddle grass, Halophila decipiens
Shoalgrass, Halodule wrightii
Turtle grass, Thalassia testudinum

Seagrass Restoration Projects

Vessel groundings and subsequent injuries are common in Biscayne National Park because of the shallow waters outside marked channels. The frequency of vessel groundings occurring within the Park is attributed in part to its proximity to the city of Miami, where recreational boating is a favorite pastime, and to the Port of Miami, which provides service for many commercial carriers, cruise ships, and barges.

Vessel grounding incidents in seagrass habitats create specific types of injuries, including cutting and scouring of the root system, displacement of sediment, and burial of seagrass. Propeller scars are formed when the propellers cut through seagrass and sediment. Blowholes are excavations of sediment and seagrass that occur during attempts by vessels to "power off" a shoal. Berm formations are often associated with propeller scars and blowholes and consist of displaced sediment that has accumulated at the edge of scars and blowholes. This burial typically results in the blockage of sunlight and smothering of bottom-dwelling organisms, including seagrass. Seagrass rhizomes grow laterally, with short shoots and blades growing upward and roots growing downward from the rhizomes. The root/rhizome system is often located several centimeters below the sediment/water column interface. Lateral growth of seagrasses is halted when grounding injuries excavate sediment support and sever rhizomes. Natural recovery from such injuries may take months to several years or longer, especially when the injury extends deep into the sediment.

When vessels run aground and injure resources in any National Park Service area, damages are sought under the Park System Resources Protection Act (PSRPA) (16 USC 19jj). The act specifically allows the Secretary of the Interior "to restore, replace, or acquire the equivalent of resources which were the subject of the action and to monitor and study such resources." The goal of seagrass restoration actions in Biscayne National Park  is to create a stable, self-sustaining environment of similar topography and sediment composition to that existing prior to injury, such that natural recovery processes, enhanced through mitigation, if needed, will lead to a fully functioning seagrass community with near natural complexity, structure, and makeup of organisms.