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Seagrasses

 

Among the most important resources in the marine environment are seagrasses. Seagrasses are flowering plants that live underwater, produce oxygen as a metabolic byproduct, have a limited depth range because of their need for light and provide many desirable functions including:

  • Maintaining water clarity by trapping fine sediments and particles with their leaves;
  • Stabilizing the bottom with their roots and rhizomes;
  • Providing habitat and nursery areas for the majority of Florida's recreationally and comercially important marine fishes, crustaceans and shellfish; and
  • Providing substrate for epiphytes, which along with seagrasses furnish food for marine animals including manatees.

Six species of seagrasses are known to occur in Palm Beach County. Turtle grass, Thalassia testudinum is capable of forming dense beds. Shoal grass, Halodule wrightii is most tolerant of temperature and salinity shanges. Manatee grass, Syringodium filiforme mixes with other species in small beds. Halophila engelmanni and Halophila johnsonii and Halophila decipiens populate deeper areas. In Lake Worth Lagoon, Halodule wrightii is the most abundant species of seagrass in terms of area coverage, and occurs primarily in shallow areas. Thalassia and Syringodium are found infrequently, and are most abundant in the north end of the Lake Worth Lagoon.

Recent studies indicate seagrasses are a scarce resource in Palm Beach County. In 1940, Palm Beach County had approximately 4820 acres of seagrass, but as of 1995, only 2510 acres of seagrass remain in County waters. The total acreage of seagrass in Palm Beach County ranked low during a 1995 assessment of seagrasses in Florida. The County ranked 28th out of 31 coastal counties surveyed.

Two major threats to seagrasses are physical damage from boat propellers and shading from moored vessels. The 1995 study indicated Palm Beach County ranked 6th highest in vessel registrations. Vessel registrations in Palm Beach County have reached 33,369 as of the 1996-97 fiscal year. 32,419 were registered as pleasure boats, while only 950 were registeres as commercial boats.

Recent studies analyzing such factors as nutrient cycling, raw materials, and support for recreational and commercial fisheries, provide a conservative estimate of the economic value of seagrasses at $20,500/acre/year. Using this value, Palm Beach County's seagrass resource would have an economic value of $51,455,000 per year. It should be noted that Chapter 376.121, F.S., deals with liability for damage to natural resources and requires compensation for seagrass and mangrove habitat loss at $1 per square foot ($43,560/acre). ERM believes this is a resource well worth protecting.

See also, Florida Department of Environmental Protection's Bureau of Protected Species Management [External Link] for additional information on seagrass protection.

2000 to 2004 Lake Worth Lagoon Seagrass Monitoring Project (Fixed Transect Monitoring)

Seagrass monitoring fixed transect locations are surveyed annually under a contract managed by ERM. Please see the report, 2000-2004 Fixed Transect Seagrass Report Adobe PDF Document [8.3MB].

2001 Lake Worth Lagoon Seagrass Mapping Project

Lake Worth Lagoon seagrass coverage was mapped under a contract managed by ERM, using 2001 1:10,000 scale true aerial photography. The resulting Lake Worth Lagoon Seagrass Map Adobe PDF Document is provided in .pdf format. The resulting GIS files are also available through downloading 2001 Seagrass ZIP File.
 

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