May 05, 2009

Although approximately 52 species of marine seagrasses exist worldwide, only seven are found in Florida waters. Four of these species are wide spread and extend well beyond Florida's borders. Ruppia maritima, commonly known as widgeaon-grass, grows in both fresh and saltwater and is widely distributed throughout Florida's estuaries.

Shoal-grass, Halodule wrightii, is an early colonizer of disturbed areas and usually grows in water too shallow for other species.

Turtle-grass, Thalassia testudinum, the most common of the Florida seagrasses, characteristically has deeper root structures than any of the other seagrasses.

Manatee-grass, Syringodium filiforme, is easily recognizable because its leaves are cylindrical.

The other three are species of Halophila: Halophila engelamannii (star grass), Halophila decipiens (paddle grass), and Halophila johnsonii (Johnson's seagrass). These small, fragile seagrasses are sparsely distributed in Florida and only limited information about them exists.

Seagrasses area valuable part of Florida's marine environment, but they are disappearing at an alarming rate. Dredge and fill projects and degraded water quality, as well as other activities, are responsible for their precipitous decline.

Along the Southwest Florida coats there are two major bay systems with similar physical features but dramatically different histories. Tampa Bay has experienced the stresses of a developed, urbanized bay system, while Charlotte Harbor, on the other hand, is one of the most natural estuaries remaining in Florida. During the past 100 years, Tampa Bay has experienced an 81% decline in seagrass acreage. From 1944 to 1982, aerial photographs showed a 29% decrease in seagrass coverage was documented in Charlotte Bay.

Department of Environmental Protection, Florida Marine Research Institute scientists are studying changes in Florida's coastal fisheries habitats. By analyzing aerial photographs from the 1940's and 1950's and satellite and aerial imagery from the 1980's, the scientists are able to evaluate habitat change in these systems.

Several sites on the east Florida coast including Ponce Inlet (just south of Daytona Beach) and the Indian River Slough (from Sebastian Inlet south to St. Lucie Inlet) have been analyzed. At the Ponce Inlet site, a 100% loss of seagrass was noted. This destruction was due primarily to dredge and fill activities for development and the Intracoastal Waterway. A seven-mile stretch of estuary surrounding the Sebastian Inlet has experienced a 38% decline in seagrass since 1951. Another study site just north of Fort Pierce Inlet was assessed for habitat change and was found to have lost 25% of the seagrass meadows that were present in 1958.

These studies documenting seagrass habitat losses in Florida are providing helpful information to local and state officials and are increasing public awareness about the problem of fisheries habitat losses and are providing incentive to address this serious problem in Florida's coastal zone.

Seagrass Monitoring in the EPA Water Quality Protection Program

Links to other websites dealing with Seagrasses.