25 May 2000 

Bill Hearn
5051 Tozour Road
Fort Fierce, Florida 34946

RE: Seagrass viability and survey techniques.

Dear Bill:

I understand that recent seagrass surveys made at our Fort Pierce Harbor study site (winter-early spring, year 2000), the same site examined by me and my colleagues during a 1990-1991 HBOI survey for St. Lucie County, indicate that seagrasses no longer occur along the western shore (facing east) opposite Fort Pierce Inlet. We had found several species there in the past. I highly recommend checking this site carefully as seagrass blades vary widely in growth with season. The rhizomes may be hidden in the sediment when the blades are not apparent.  This is particularly true for the winter. I recommend a summer survey to be certain that there are not seagrass growing at the site. I have observed the endangered seagrass, Halophylajohnsoni, making an appearance at this site during the spring and summer months.

Long term studies of seagrasses in the Indian River Lagoon conducted by Bob Virnstein, of the St. Johns River Water Management District and my colleagues at the Kennedy Space Center, Mark and Jane Provancha of Dynamac Corporation, have also demonstrated that seagrass may also show great annual variation. A single annual survey could be misleading. If seagrasses were there, and they were, I strongly suggest going through the prime growing season, spring and summer, as well as giving it another year to determine if they are actually gone.  A multi-annual change from seagrass to the tropical algae, Caulerpa, occurred in the Banana River Lagoon and caused considerable concern. However eventually the algae declined and the same location reverted back to very productive seagrass meadows. Seagrass are not like oak trees. Grasses and seagrasses have considerable seasonal variation, and take advantage of optimum water depths, water quality and substrates for growth.  Extreme variation in storms and rain runoff last fall could have influenced seagrass growth at this site as it is adjacent to Taylor Creek. This is very likely an ephemeral event and effect. Since seagrasses grew at the site in the recent past, they should return there in the future under the right conditions, or may be there now in a dormant condition. Only a thorough survey which includes rhizome examination over several months will determine, their presence or absence.

These observations are based on nearly 30 years of studying Indian River Lagoon seagrass meadows and the diverse animal community dependent on them. This was also the topic of my doctoral dissertation 
(Subtropical Seagrass Fish Communities: Population Dynamics, Species Guilds and Microhabitat Associations in the Indian River Lagoon, Florida, FIT, 1988). This work was based on 1.98 million fish examined between Sebastian and St. Lucie inlets, and centered on Fort Pierce Inlet. These data indicated that each hectare of seagrass specifically in Fort Pierce Inlet supports an average of 14,569 fish annually. I recorded 164 fish species in fifty-four families from these quantitative seagrass community studies. One single ocean inlet 50 foot seine haul contained 56 fish species. That is a diversity record that has not been broken anywhere in the United States.

Considering the overwhelming value of ocean inlet seagrasses to the continental shelf, reef and lagoon fisheries no one should take seagrass growth lightly. This fishery is valued in the hundreds of millions of dollars for the Florida east coast alone. It has been thoroughly demonstrated that Fort Pierce Inlet seagrasses support valuable mutton and lane snapper, gag and scamp grouper flsheries. Fort Pierce lnlet is particully important as it is larger than the other IRL inlets and is, therefore, the major oceanic and marine organism access point to the Indian River Lagoon.

The high biodiversity of the Indian River Lagoon is the reason the IRL was designated by EPA as an estuary of national significance. The great number of aquatic species is due to the high biological diversity of inlet seagrass meadows, principally those at Fort Pierce and St. Lucie inlets. Therefore, each square meter of seagrass in Fort Pierce Inlet is a national treasure supporting the highest estuarine biodiversity in the United States. I recommend very careful examination and time allotted for the most thorough examination of seagrass presence or absence.

I have enclosed two of my published manuscripts which document the biological diversity of seagrasses and the Indian River Lagoon. My dissertation is available through the FIT library and gives quantitative information on Fort Pierce Inlet seagrass meadows.

If I can be of further help let me know.

Sincerely,
R. Grant Gilmore, Jr., Ph.D.
Senior Aquatic Scientist