ABSTRACT

9910514
Childers
Estuaries and coastal landscapes experience a range of stresses, both natural and anthropogenic. Among these, cultural eutrophication affects most US coastal ecosystems. As a results, most coastal ecological research has been conducted in systems that are experiencing eutrophication. This coastal Everglades LTER will investigate how variability in regional climate, freshwater inputs, disturbance and perturbations affect land-margin ecosystems. This coastal site is particularly appropriate for studying these questions because the entire systems is oligotrophic, it is the focus of the largest watershed restoration effort ever implemented, and freshwater flow is controlled in different ways by the highly variable precipitation regime and water management. The long-term research program will focus on the central idea that regional processes mediated by water flow control population and ecosystem level dynamics at any location within the coastal Everglades landscape. This phenomenon is best exemplified in the dynamics of an estuarine oligohaline zone where fresh water draining phosphorus-limited Everglades marshes mixes with water from the more nitrogen-limited ocean. This central idea along with a series of specific hypotheses will be tested along freshwater to marine gradients in two Everglades drainage basins. A clear productivity peak has been observed in the low salinity zone of one basin, but not the other. This peak appears to be the result of low P, high N freshwater meting higher P, lower N marine water. Nutrient generation from dissolved organic matter (DOM) will be quantified because it is expected to be a major contributor to this oligohaline production peak. The role of the microbial loop in affecting secondary production will also be investigated. Essentially, his LTER project will focus on how changes in freshwater flow and climatic variability control the relative roles that nutrients and organic mater play in regulating estuarine and coastal productivity.
The transect design is conceptually analogous to a Lagrangian approach in which parcels of water are followed as they flow through freshwater marshes and mangrove estuaries to offshore. Along the way, patterns and processes in the water and in the wetlands though which it is flowing will be quantified using long-term sampling and short-term mechanistic studies. Primary production, concentrations and turnover dynamics of inorganic nutrients and organic matter (particularly DOM), organic mater accretion and turnover in soils and sediments, and consumer dynamics and productivity will be measured. Process based simulation models will be used to link key components, such as relationships between DOM quantity and quality, microbial loop dynamics, and higher trophic levels. Data synthesis will also include hydrologic models to simulate water residence times along the transects, and a GIS-based project database that will integrate data from this LTER research with information from other related projects. The GIS database will be linked to the coastal Everglades LTER web site to maximize the exchange and dissemination of information within the LTER Network and with the scientific community in general.

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