Seagrasses

Seagrass is an angiosperm (flowering plant) that lives in a marine or brackish environment. There are about 50 species of true seagrasses worldwide that are found within the plant families Posidoniaceae, Zosteraceae, Hydrocharitaceae, and Cymodoceaceae. Seagrasses are sometimes found in patches, but these patches can expand to form huge seagrass beds, or meadows. The beds can be made up of one species of seagrass, or multiple species.

Seagrasses require lots of light, so the depths at which they occur in the ocean are limited by light availability. Seagrasses are found in protected coastal waters such as bays, lagoons, and estuaries and in both temperate and tropical regions.

Seagrasses may be confused with seaweeds (marine algae), but they are not. Seagrasses are vascular plants and reproduce by flowering and producing seeds. Marine algae are classified as protists (which also includes protozoans, prokaryotes, fungi and sponges), are relatively simple and reproduce using spores.

Seagrasses attach to the ocean bottom by thick roots and rhizomes, horizontal stems with shoots pointing upward and roots pointing downward. Their roots help stabilize the ocean bottom. In addition to stabilizing the ocean bottom, seagrasses help with water clarity by trapping sediments and small particles in the water column, and help boost local economies through supporting vibrant recreation opportunities.

Seagrasses provide an important habitat to a number of organisms. Some use seagrass beds as nursery areas, others seek shelter there their whole lives. Larger animals such as manatees and sea turtles feed on animals that live in the seagrass beds.

Organisms that make the seagrass community their home include bacteria, fungi, algae; invertebrates such as conch, sea stars, sea cucumbers, corals, shrimp and lobsters; a variety of fish species including snapper, parrotfish, rays, and sharks; seabirds such as pelicans, cormorants and herons; sea turtles; and marine mammals such as manatees and bottlenose dolphins.

• Natural threats to seagrasses include storms, climate changes such as floods and droughts affecting water salinity, disruption of seagrasses by small predators as they search for food, and grazing by animals such as sea turtles and manatees.
• Human threats to seagrasses include dredging, boating, water quality degradation due to run-off, and shading of seagrasses by docks and boats.

• Florida Museum of Natural History. 2008. ”Seagrasses”. (Online) Florida Museum of Natural History. Accessed November 12, 2008.
• Florida Fish and Wildlife Conservation Commission. 2008. ”Learn About Seagrasses” (Online). Florida Fish and Wildlife Conservation Commission Fish & Wildlife Research Institute. Accessed November 12, 2008.
• Florida Department of Environmental Protection. 2008. ”Seagrasses” (Online). Florida Department of Environmental Protection. Accessed November 12, 2008.
• Seagrass.LI, Long Island’s Seagrass Conservation Website. 2008. ”What is Seagrass?” (Online). Cornell Cooperative Extension Marine Program. Accessed November 12, 2008.