| Abstrakt: |
The fauna of seagrass-covered mud banks in Florida Bay, documented in the mid 1980s prior to recent seagrass die-off, phytoplankton blooms, and other ecosystem changes, was reexamined in the mid 1990s for faunal changes that might be associated with environmental perturbations. During both decades, decapod crustaceans and fishes were collected with 1-m2 throw traps from seagrass beds at six sites that differ in the amount of freshwater and/or marine influence and in seagrass community metrics. The most common faunal changes were declines in seagrass-canopy-dwelling forms and increases in benthic forms.At three sites with relatively lush seagrass meadows, above-ground seagrass standing crop declined and abundance of the benthic predatoryfish Opsanus beta increased. The degree of faunal change among thesesites appeared to be related either to salinity variability or to the degree of exposure to the ecosystem changes that have taken place in Florida Bay. At two sites with poorly developed seagrass meadows, seagrass standing crop and canopy height did not change significantly between decades, but there was an increase in shoot density and totalleaf area. The animal communities at these sites were characterized by significant increases in the abundance of benthic crustaceans. At the site on the edge of Rankin Lake, the basin where seagrass die-offwas first observed in Florida Bay during 1987, seagrass standing crop, canopy height, shoot density, and leaf area declined significantlybetween decades, but species richness of both crustaceans and fishesincreased. The abundance of canopy-dwelling crustaceans and fishes declined markedly at this site, whereas the abundance of benthic formsless dependent on seagrass cover generally increased. In retrospect,we believe the fauna at this site during the 1980s, characterized byhigh productivity but few species, was already showing signs of the stresses that led to the seagrass die-off that began in 1987. [ABSTRACT FROM AUTHOR] |
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