Indian River Lagoon Seagrass

Seagrass Monitoring and Restoration: Seagrass is the key resource on which the Coastal Basins Section focuses. This is primarily because as a habitat it sustains a fishery valued in the hundreds of millions of dollars per year, but also because it is a good indicator of the overall health of the lagoon ecosystem and is strongly (negatively)impacted by reductions in water quality/ clarity/ salinity. Seagrasses are vascular, flowering plants, not algae. The seven species which occur in the Lagoon system belong to three different families. The Lagoon has the highest diversity of seagrass species in the entire Western Atlantic / Caribbean region, and one species Halophila johnsonii, is virtually endemic, only occurring along the east coast of Florida from Sebastian Inlet to Biscayne Bay. Seagrass meadows play the role of nursery substrate for various species of commercially important fish which spawn in the Lagoon and also of forage for marine herbivores such as fish, green sea turtles and manatees. Seagrass monitoring is done in two ways: a) Seagrass mapping is conducted every two years (and in addition, 2006) based on interpretation of 1:24,000 aerial photos by an outside contractor (Avineon, etc). 2007 is the most recent mapped year. Mapped seagrass coverages exist for 1943, 1986, 1989, 1992, 1994, 1996, 1999, 2001 (partial), 2003, 2005, 2006, and 2007. b) Field monitoring of 85 fixed transects in the Lagoon occurs semiannually, January-February and July-August. Transects are evaluated every 10 m for species present, percentage cover, presence of epiphytes and macroalgae, canopy height, water depth, light availability and distance from shore at deep edge of seagrass bed.

A primary objective of the Indian River Lagoon (IRL) Surface Water Improvement and Management (SWIM) Plan is to protect and restore seagrasses. The IRL SWIM Plan directs the South Florida and St. Johns River Water Management Districts to map seagrasses in the Indian River Lagoon at two to three year intervals. These lagoon-wide maps, based on aerial photographs, provide an overall picture of the seagrass resources in the IRL. These maps serve as important management tools for obtaining a current inventory of this resource, identifying "healthy" areas that may deserve special protection efforts, and identifying potential "problem" areas that require further investigation. The maps can also document large-scale trends in the status of this resource.