Coastal Services Center

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Touch Tank: Johnson's Seagrass (Halophila johnsonii)

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Johnson's seagrass (Halophila johnsonii) is found only along the Florida coast. Courtesy: NOAA Coastal Services Center

What type of habitat does Johnson's seagrass prefer?
Johnson's seagrass prefers to grow in coastal lagoons in the intertidal zone. This species prefers sandy bottoms for growing and is often found in deeper waters than other seagrasses.

Where can it be found in the coastal U.S.?
Johnson's seagrass is only found in southeastern Florida – from Sebastian Inlet to Biscayne Bay.

What does Johnson's seagrass look like?
Johnson's grass has short, elliptical shaped leaves that grow in pairs. The leaves reach up to 2.5 cm long and up to 4 mm wide. The leaves are not serrated and the stem growing from the rhizome (creeping root-like structure) is 1 to 2 cm long.

Why is it an important benthic species?
This threatened species of seagrass serves as a food resource for other threatened and endangered species, including green sea turtles and West Indian manatees.

Did you know…?
This species only occurs in southeast Florida and thrives in areas at high risk to damage from boat propellers and water quality degradation. Because it has never been known to reproduce sexually, it is believed to only reproduce by spreading from its rhizomes. Because of its limited range, high damage risk, and slow reproduction, the U.S. Fish and Wildlife Service has classified Johnson's seagrass as a threatened species.

Where can I find more information?

• NOAA's NMFS Office of Protected Resources Johnson's Seagrass (Halophila johnsonii) Web page
• Smithsonian Marine Station at Fort Pierce's Halophila johnsonii Web page

Reference
Meñez, E. G., and R. C. Phillips. 1998. Seagrasses. Smithsonian Institution Press. Washington, D.C.

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