Johnson’s sea grass

 Sea grasses are plants found in intertidal zones and shallow marine waters.  Most resemble terrestrial grasses and grow in what appears to be large “meadows” in tropical and temperate waters.  Johnson’s sea grass is one of the rarest of the various species of sea grass.  It is found only in small isolated patches along the Atlantic coast of Florida between Sebastian Inlet (south of Cape Canaveral) and the northern portion of Biscayne Bay.  Most sea grasses reproduce both sexually and clonally (i.e., a sexually).  Johnson’s sea grass only reproduces clonally, placing it at a competitive disadvantage.  Clonal reproduction also implies that the plants alive today are virtually unchanged from those growing tens of thousands of years ago.  The smooth leaves of Johnson’s sea grass grow in pairs up to about one inch in length, on a creeping rhizome on the sandy or muddy bottom.  Like other sea grasses, it plays an important role in its ecosystem, serving as a shelter and nursery habitat for small animal life.  It is also a food source for various animals, including manatees and sea turtles.  Being heavily dependent upon substrate stability, Johnson’s sea grass is highly susceptible to habitat degradation.  Small boats have had a significant impact upon the species due to propeller scarring, anchoring, and mooring.  Dredging of the intertidal areas also has adverse consequences for the rare species.  Storms, sedimentation, and nutrient enrichment for urban and agricultural runoff have also stressed the sea grass.  In 1998, the National Oceanic and Atmospheric Administration (NOAA) listed Johnson’s sea grass as threatened.  Its critical habitat (see above) was officially designated in 2000 and a recovery plan was promulgated in 2002.  Research is underway to grow Johnson’s sea grass in captivity.