Identification of Florida's Seagrasses

Marine flowering plants or "seagrasses" are angiosperms and unlike algae, have true roots, stems and leaves. All of the previously mentioned plant organs contain vascular tissue. In contrast with the algae, seagrasses produce flowers and seeds, although the flowers are often inconspicuous. In terrestrial environments the flowering plants often dominate the landscape in contrast with marine environments where the algae are usually the dominant plant life. There are exceptions to this general observation, where one can see submerged "meadows" of seagrasses often dominated by one species such as Thalassia testudinum or Turtlegrass on flat sandy bottoms. These are often referred to as seagrass flats and are an important natural resource that has a significant biological role, directly linked to commercially important marine life. Seagrasses are one of the most productive plant communities on the planet and part of the base of the food chain in Florida's marine environment. There are an estimated 2,000,000 acres of seagrass in Florida waters of the Gulf of Mexico and Florida Bay (over 1,000,000 acres in Florida Bay alone). Some 700,000 acres of seagrass exist in the east coast waters of the state from the middle of Mosquito Lagoon to the lower portion of Biscayne Bay. Florida has an estimated 1,000,000 acres of seasonal seagrass in deeper coastal marine waters as well. Unfortunately tremendous losses of this irreplaceable habitat have occurred along both coasts of Florida mostly due to pollution and the effects of coastal development.

Key to marine seagrass species
Click on the links to see an picture of the seagrass species.

Vegetative Key

1. a) Plants with flat leaf blades ..... 2

b)  Plants with round or cylindrical leaf blades..... Syringodium filiforme (syn: Cymodocea filiformis) [Manatee-Grass]

Syringodium filiforme

2. a) Leaves elliptic, oval or oblong, each associated with 2 scales at the base…..3

b) Leaves flat or threadlike……4

3. a) Leaves in a pseudowhorl, each with 2 scales at the base and two scales halfway up the petioles or leaf stem…..Halophila engelmannii [Star Grass]

Halophila engelmannii

b) Leaves paired…..5

5. a) Leaves rounded, generally oval in shape, secondary veins at an angle greater than 45 degrees, leaf margins with minute serrations, annuals…..Halophila decipiens [Paddle grass]

Halophila decipiens

b) Leaves with a pointed tip, secondary veins at an angle of approximately 45 degrees or less, elongated, entire, perennials…..Halophila johnsonii [Johnson’s seagrass]

Halophila johnsonii

4. a) Leaves threadlike from a branched stem, leaf tip pointed…..Ruppia maritima [Widgeon grass]

Ruppia maritima

b) Leaves flat, leaf tip is rounded or truncated…..6

6. a) Leaf blades greater than 3 mm in width, generally about 1 cm wide, plants with scaly rhizomes…..Thalassia testudinum [Turtle grass]

Thalassia testudinum

b)  Leaf blades generally less than 3 mm in width, plants without scaly rhizomes…..Halodule wrightii [Cuban shoal grass]

Habitat Protection

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