SPATIOTEMPORAL PATTERNS OF THE SEAGRASS THALASSIA TESTUDINUM IN THE FLORIDA KEYS NATIONAL MARINE SANCTUARY
Rose, C.D. and Fourqurean, J.W.
Department of Biology and the Southeast Environmental Research Program, Florida International University, University Park, Miami, Florida, 33199

In this paper we present data from an on-going seagrass monitoring program in the Florida Keys National Marine Sanctuary (FKNMS) focusing on patterns and variability of blade productivity of the seagrass Thalassia testudinum (turtle grass). Data have been collected 4 times from December 1995 through December 1996 from 26 permanently established stations in the FKNMS. Sites were surveyed using Braun-Blanquet transects, and blade productivity of T. testudinum was measured using a modification of Zieman's (1974) leaf-marking technique in 6 replicate quadrats at each site. Density, standing crop, and blade productivity, of T. testudinum is extremely variable and peaks during the summer. Productivity ranged between 0.18 - 8.31 mg SS-1 d-1 and increased by ~390 % from December 1995 to August 1996, which corresponded with increases in density (~ 40 %), abundance (~ 50 %), and standing crop (~ 87 %). Due to the large number of variables (22) and significant correlations within the data set, Principal Components Analysis was utilized to reduce the analysis to 6 independent principal components that described ~ 81 % of the total variation in the data. Temporal and spatial analysis of these components were used to describe large-scale or regional patterns of seagrass communities in the FKNMS, including the effects of seasonality, water depth, nutrient availability, seagrass density, and macrophyte species composition.