Johnson's Seagrass (Halophila johnsonii)

                  

                                        Johnsons' Seagrass Bed: Photo Credit Lynn Lefevbre

Species Description

Johnson's seagrass can be identified by its smooth margins, spatulate leaves in pairs 0.25 to 1 inch (0.5-2.5 cm) long, a creeping rhizome (a horizontal subterranean plant stem, like the runners on a strawberry plant) with petioles, sessile (attached to their bases) female flowers, and longnecked fruits. The male flowers are unknown.

Outstanding differences between Johnson's seagrass and other similar species are its distinct asexual reproduction and leaf shape and form. The species is known to reproduce only asexually and may be limited in distribution because of this characteristic.  Johnson's seagrass plays a major role in the health of "benthic" resources as a shelter and nursery habitat. It has been documented as a food source for endangered West Indian manatees and threatened green sea turtles. NOAA's National Marine Fisheries Service (NMFS) continues to conduct ecological research on Johnson's seagrass to better understand its life history and inform conservation decisions affecting the seagrass ecosystems.

ESA Listing Information

• December 4, 2007 - Johnson's Seagrass 5 -Year Review (72 FR 68129)
  • Notice of Availability of Johnson's Seagrass 5 Year Review

 

• September 14, 1998 - Final Listing Rule (63 FR 49035)

• October 15, 1997 - Status Review

Critical Habitat

• April 5, 2000 - Critical Habitat Designation (65 FR 17786)

• Critical Habitat Maps and GIS Data

Recovery Plans

• October 4, 2002 - Johnson's Seagrass Recovery Plan (67 FR 62230)

Supplemental Information on Johnson's Seagrass

• Johnson's Seagrass Image Gallery

• The Effects of Docks on Seagrasses, With Particular Emphasis on the Threatened Seagrass, Halophila johnsonii (2008)

• Johnson's Seagrass Fact Sheet
  
  
• Johnson's Seagrass Construction Key
  

For additional information on this subject contact: Shelley Norton (727) 824-5312