Contact: Michael J. Durako, Associate Professor, the University of North Carolina at Wilmington, Center for Marine Science Research, Wilmington, NC 28409.

Margaret O. Hall, Research Scientist, Florida Marine Research Insitute, 100 Eighth Ave. S.E., St. Petersburg, FL 33701

The approach utilized in the Florida Bay FHAP program for assessing status and trends in benthic fish habitat in Florida Bay is based on a three-tiered effort. Simlar approaches are also being applied in the FKNMS seagrass monitoring program and the DERM program in northeast Florida Bay, thus providing a mechanism for the establishment of a regional management-oriented database. The study elements outlined below provide information for spatial assessment and resolution of both intra- and inter-annual variability in the macrophyte (seagrasses and macroalgae) communities and will provide spatially-explicit change data to monitor responses of these important benthic communities to possible future water management alterations of other restoration activities.

I. Abundance and distribution: This study element will assess the species distribution and relative abundance of macrophytes at a bay-wide scale. Sampling is conducted twice-yearly, during the spring (April/May) and the early fall (October/November) at more than 300 stations. Species distribution and abundance of macrophytes is assessed using a modified Braun-Blanquet frequency/abundance scale. At each sampling station, short-shoots may also be collected to be screened by the Aquatic Health Group at FMRI for the presence of Labyrinthula and related microbes. In each of the ten selected basins, station locations are randomly chosen from within each of about 30 fixed, tesselated hexagonal grids. This type of sampling design, results in systematic random sampling, scales the sampling effort to the size of the basin, and results in superior interpolated (kriged) map products. Contour maps of species distribution and abundance and maps of intra- and interannual changes in these characteristics will be produced.

II. Structure and dynamics : This study element will assess the spatial and temporal variability of seagrass-habitat structure and dynamics (ecoindicators). Structural characteristics of the benthic macrophyte communities (standing crop for all macrophytes; seagrass short-shoot morphometrics:short-shoot and apical density, leaf area index, leaf length and width, shoot age) are being determined during the spring Braun-Blanquet sampling. At each station, a quantitative core sample is taken in one of the four Braun-Blanquet sample quadrats. Contour maps of quantitative characteristics will be produced and the quantitative data will be compared with the visual data.

III. Population dynamics: An examination of the population age structures and demographics of Thalassia is being conducted to determine the efficacy of the recently developed reconstructive aging technique to assessing population health. Estimates of short-shoot recruitment, mortality, shoot turnover rates, mean, median and maximum shoot ages, and cumulative age structure in this dominant seagrass will be calculated. These indices will be examined to assess population status in terms of predicted population expansion or decline. Age information will be gathered using leaf scar counts (=plastochrone intervals) from short-shoots collected at each Spring Braun-Blanquet station. Conversion of plastochrone intervals to chronological time will be accomplished by using both leaf-punch data and cohort analyses.