St. Marks National Wildlife Refuge
Southeast Region
Map of the Southeast Region Map of Kentucky Map of the Caribbean and Navassa Map of North Carolina Map of Tennessee Map of South Carolina Map of Arkansas Map of Louisiana Map of Mississippi Map of Alabama Map of Georgia Map of Florida

Marine Plants Factsheet

Salt marshes – aka, tidal marshes because they occur in zone between low and high tides. They thrive along low energy coastlines. Also occur in estuaries, where fresh and saltwater mix. Composed of rushes, sedges and grasses. Distinctive feature is color – brown, green & gray. Florida ’s dominant salt marsh species include:

  • smooth cord grass (Spartina alterniflora) – most frequently inundated areas
  • salt meadow cord grass (Spartina patens) – periodically inundated areas
  • black needle rush (Juncus roemerianus) – grayish, in higher ground areas

Importance of salt marshes:

  • Provide cover for animals to hide from predators
  • Habitat for juvenile fish species ( nursery for 70 % of Florida ’s economic and recreational species of fish, shellfish and crustaceans)
  • Dead plants decompose and make organic detritus, a food source for many marsh species
  • Epiphytic algae is an important food source as well
  • Extensive root systems help buffer land from storm surge
  • Filter nutrients and pollutants and help control sediments

Seagrasses - 52 species worldwide, 7 in North America and Florida and 6 in Big Bend :

  • Star grass Halophila engelmannii
  • Paddle grass Halophila decipiens
  • Widgeon grass Ruppia maritime
  • Turtle grassThalassia testudinum
  • Shoal grass Halodule wrightii
  • Manatee grass Syringodium filiforme

Sea grasses are true flowering plants with leaves, stems, roots and flowers. They are vascular plants, meaning they contain vessels that conduct fluids up and down the plant. Flowering plants are not abundant in the ocean. Marine grasses and mangrove trees are among the few vascular plants that grow in salt water. Further south in FL peninsula, mangroves outcompete seagrasses. Direct food source for manatees, sea urchins, loggerhead and green sea turtles. Many other species eat algae and decaying plants.

Other marine plants – Algae

Algae are non-vascular plants, w/o roots, stems, leaves or flowers. Pelagic algae, i.e., algae that live in the water column are known as phytoplankton, free floating, unattached plants, usually unicellular and microscopic. Attached algae are multi-cellular, readily visible and distinguished by their dominant color-- blue green, green, red and brown. Algae are producers of organic material and animal life depends on it as a food source. Through photosynthesis, algae releases large amounts of oxygen into the water. As a water planet, most of the world’s supply of oxygen is by marine vs. terrestrial plants.

Last updated: August 17, 2010