Seagrass Research

Syringodium filiforme is shaped very differently from all other Florida seagrasses because its leaves are cylindrical, not flat. Manatee grass cannot tolerate large swings in salinity, it prefers salinities between 15-36. It looks like green spaghetti but does not taste like it, well, maybe to a manatee!

Halodule wrightii grows throughout Florida. Its leaves are narrow and flat with a square tip. It can tolerate a wide range of salinities and is considered a pioneer species, often the first to colonize a disturbed area. Shoal grass is thus named because it can grow in water too shallow for most seagrasses, often on shoals that can be exposed at low tide.

Ruppia maritima is the only seagrass species able to grow in both fresh and saltwater. It is typically found in the lower salinity areas of Florida estuaries. Like shoal grass, widgeon grass has narrow, flat blades but with pointed tips. The two are hard to tell apart, but widgeon grass is easily distinguished from shoal grass when it flowers.

Halophila engelmannii is 1 of 4 species of the genus Halophila found in Florida and is the only species found in Tampa Bay. It is the easiest species of Halophila to identify because of its whorl of 5-7 leaves. Halophila often grows among other seagrasses forming an understory to the seagrass canopy. They can also grow at greater depths than other seagrasses, occasionally over 100 ft deep!

Halophila decipiens is a diminutive seagrass with paddle-shaped leaves. This species inhabits both shallow and deep coastal waters and has been found up to 115 feet deep! At a maximum of 1 inch tall, it is one of Florida’s smallest seagrasses. Paddle grass is one of the few seagrasses that can be found worldwide.

Halophila ovalis, formerly known as Halophila johnsonii, is a small seagrass found in Florida primarily in the Indian River Lagoon. Previously believed to be endangered, it is now recognized as an introduced species from the Indo-Pacific. All of Johnson’s seagrass found in Florida is believed to be a single female clone (Waycott et al. 2021), spreading through clonal growth and fragmentation. Although Johnson's seagrass is no longer protected by the Endangered Species Act, the South Atlantic Fishery Management Council designates all seagrasses as “Essential Fish Habitat" and "Habitat Areas of Particular Concern" under the Magnuson-Stevens Fishery Conservation and Management Act. Therefore, all seagrass species in Florida retain federal protections (NOAA).

Halophila stipulacea is a small, tropical seagrass native to the Indian Ocean, Persian Gulf and Red Sea. It migrated to the Mediterranean through the Suez Canal in 1941 and was observed in the Caribbean in 2004. This seagrass fragments easily, grows quickly, and is believed to travel to new locations by ship traffic. It was first observed in Florida in fall of 2024 in Biscayne Bay.  

Learn more about the FWC’s response to this seagrass.