At first glance the sawgrass prairie wetlands that make up a large part of the Everglades ecosystem in south Florida appear uniform across the landscape. From the air, except for the interspersed hardwood hammocks and the obvious vegetational differences along entrenched waterways, the sawgrass appears homogeneous and unchanging. This ecosystem, however, is extremely heterogeneous. This is due to the presence of micro-habitats that vary both spatially (horizontally and vertically) and over time (seasonally and longer). The forces that drive this heterogeniety include obvious, dominant physiographic characteristics such as climate, topography, and underlying geology. They also include less obvious, subtle forces such as wet-dry cycles, organic matter accumulation, trace element mobilization and transport, and the influence of human activities. These forces govern the dynamic chemical, physical, and biological processes that define the sawgrass ecosystem. An important concept to understand is that this ecosystem is highly variable and by understanding the magnitude of the variability we are better able to define the critical processes that drive the ecosystem.

Agricultural practices and the management of surface water flow, occuring in and near the Everglades Agricultural Area (EAA) south of Lake Okeechobee, are important contributing factors in observed recent changes in the sawgrass prairie. The flow of waters enriched in nutrients is thought to play a role in mercury accumulation and cycling and in changes in vegetation communities (especially changes in algal populations and an increase in cattail and the decrease in sawgrass). It is believed that a variability gradient in this influence occurs primarily from north to south; however, the relative importance of surface vs. ground water flow patterns, and the associated hydro-geochemistry, has not been defined.

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