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Learn About Seagrasses


Seagrasses are flowering plants found in shallow coastal marine waters. Since they evolved from land plants millions of years ago, seagrasses are significantly different than seaweed (algae) in their ecology, morphology, and physiology. While both algae and seagrasses have photosynthetic capabilities, algae obtains its nutrients directly from the water through diffusion, and seagrasses use their leaves and roots to obtain nutrients from sediment and water. Each of the seven species of seagrasses found off Florida's coast has unique physical requirements for survival, such as light, salinity, and nutrient availability. The amount of light available to seagrasses is one of the primary determinants of the maximum depth at which these plants can grow, since a lack of light interferes with their ability to produce food. In areas where water quality and clarity are poor, seagrasses may only be found in the most shallow waters.

Seagrass beds typically begin as small, patchy beds where sediment conditions in otherwise barren areas have changed just enough to encourage colonization by new species. If water quality and sediment conditions remain optimal and disturbances are minimal for many decades, these small patches can join to form large, continuous beds known as seagrass meadows.

Seagrasses are important to Florida in many ways. They provide food and habitat to numerous marine species, stabilize the ocean bottom, maintain water quality, and help support local economies. The threats facing seagrasses could cause local or even regional die-offs, which can affect many aspects of human life. Some of the natural occurrences that can threaten seagrass survival include storm activity and other climate changes. The wave energy introduced by storms can uproot seagrasses and cause extensive damage. Other climate conditions, such as floods and droughts, can affect seagrasses by changing the salinity of the water, which can affect their distribution. Grazing is another natural factor affecting seagrasses: some marine animals, such as the endangered Florida manatee and green sea turtle, feed directly on seagrasses. Many smaller organisms forage for food within seagrass beds: crabs, fish, skates, and rays can disturb seagrasses during their search for food. In addition to these natural threats, humans can damage seagrass communities through activities such as dredging and boating. Run-off is another major problem because it can change water quality and reduce the amount of light reaching these plants. Docks and boats can shade seagrass beds, causing them to die from lack of light.

You can help protect seagrasses:

  • Practice smart boating by avoiding navigation through shallow grass beds.
  • To avoid contributing to the problem of changing water chemistry through run-off, be careful when applying fertilizers and pesticides. Rain can wash excess chemicals into rivers or other water bodies which drain into the sea.
  • To allow sunlight to penetrate to grasses living below docks, consider using grating rather than planks when building or repairing a dock.

FWRI scientists are involved in many research projects that help increase the available knowledge about seagrasses and improve the state's ability to protect this important ecosystem. These include mapping seagrass distribution, examining possible links between sediment nutrients and phytoplankton blooms, and measuring changes in light available to seagrasses. FWRI staff members and other agencies and organizations throughout Florida also explore many seagrass management and restoration options.

Further information can be found by following the links within this article, which can also be accessed from the main seagrass page. The links page lists Web sites that provide useful information on seagrasses and the publications section lists FWRI documents that are available for download.