The Florida coastal Everglades (FCE) is a coastal wetland, which is characterized by a freshwater to marine gradient ranging from freshwater marshes, through mangrove fringe to the seagrass dominated Florida Bay estuary. Dissolved organic matter (DOM) in this system is am important biogeochemical component as most of the N and P are in an organic form. The dynamics of this DOM in the FCE is complex given its versatile sources and the effects of geomorphology, hydrology, water chemistry, and history of degradation on DOM composition and fate. Thus, in order to determine the sources, transport and fate of DOM in this ecosystem, long term studies and large datasets are required to produce a significant assessment.

In this study, we provide long-term data (4 yrs) from monthly surface water samples collected at fifteen sampling stations. We applied a rapid and sensitive spectroscopic method, namely Excitation Emission Matrix (EEM) fluorescence coupled with Parallel Factor Analysis (PARAFAC) in an attempt to assess compositional variations of DOM on both spatial and temporal scales in the Everglades. Eight fluorescence components were modeled through PARAFAC, and these presented clear spatial and seasonal trends. For example, freshwater marsh DOM was enriched in terrigenous compounds, while estuarine sites were more enriched in microbial-derived, algal carbon inputs. Coastal estuarine sites were significantly controlled by hydrology, while DOM dynamics in Florida Bay were seasonally driven by primary productivity and hydrology. Freshwater marsh sites were enriched in terrestrial components especially during the dry season reflecting soil and groundwater sources, while the wet season was more enriched in microbial components likely derived from periphyton. Peat-based sites could be clearly differentiated from marl-based sites based on EEM-PARAFAC data.

Combined with other photo-and bio-degradation and with groundwater data, the identified EEM-PARAFAC components were found to potentially serve as not only source proxies, but also diagenetic status indicators. For example, components could be correlated with photochemical processing of DOM. Several aspects of this work will be presented with the objective of demonstrating the potential applications of EEM-PARAFAC in the LTER program.