DEVELOPMENT OF PLANTED SEAGRASS BEDS IN TAMPA-BAY, FLORIDA, USA .1. PLANT-COMPONENTS

In this study we evaluated the floral attributes of planted seagrass b eds as they developed over time. The seagrasses Halodule wrightii and Syringodium filiforme were planted on 0.5 m centers at several sites w ithin Tampa Bay, Florida, USA. Planting unit (PU) survival, change in areal shoot density, plant morphometrics and associated macroalgae wer e monitored over a 3 yr period. These parameters were compared with ne arby, natural beds as a reference. Comparisons were not limited to the same species, but included Thalassia testudinum in order to address m anagement issues regarding the substitution of one habitat type for an other. Despite use of experienced personnel, in some plantings, an ave rage 47% loss of PU was sustained, apparently due to seasonal bioturba tion. Depending on the spatial distribution of loss, persistent cover at equivalent densities was still attained within 1.8 yr (for planting s on 0.5 m centers) over portions of some planted sites. Seagrass reco very rate and recommended monitoring times have a positive, linear rel ationship to spacing of plantings. Although moderately variable, areal shoot density clearly defined trends in bed development over time. Ma ny plantings exhibited little spread in the first year after planting, and then expanded rapidly in the second year. Seagrass surface area, length or biomass, as well as macroalgal biomass, proved to be weak in dicators of system development for most seagrass species. Although sub stantial PU losses were experienced, the subsequent survival, spread a nd persistence of seagrasses indicate that large areas of Tampa Bay, w hich historically had supported seagrass, are now suitable for restora tion. For remaining seagrass habitat however, conservation provides a more certain basis for maintaining the resource than attempting to mit igate through planting.