Using fluorescence spectroscopy to trace seasonal DOM dynamics, disturbance effects, and hydrologic transport in the Florida Everglades

Dissolved organic matter (DOM) quality reflects numerous environmental processes, including primary production and decomposition, redox gradients, hydrologic transport, and photochemistry. Fluorescence spectroscopy can detect groups of DOM compounds sensitive to these processes. However, different environmental gradients (e.g., redox, DOM provenance) can have confounding effects on DOM fluorescence spectra. This study shows how these confounding effects can be removed through discriminant analyses on parallel factor modeling results. Using statistically distinct end‐members, we resolve spatiotemporal trends in redox potential and DOM provenance within and between adjacent vegetation communities in the patterned ridge and slough landscape of the Everglades, where biogeochemical differences between vegetation communities affect net peat accretion rates and persistence of landscape structure. Source discrimination of DOM in whole‐water samples and peat leachates reveals strong temporal variability associated with seasonality and passage of a hurricane and indicates that hurricane effects on marsh biogeochemistry persist for longer periods of time (>1 year) than previously recognized. Using the DOM source signal as a hydrologic tracer, we show that the system is hydrologically well mixed when surface water is present, and that limited transport of flocculent detritus occurs in surface flows. Redox potential discrimination shows that vertical redox gradients are shallower on ridges than in sloughs, creating an environment more favorable to decomposition and diagenesis. The sensitivity, high resolution, rapidity, and precision of these statistical analyses of DOM fluorescence spectra establish the technique as a promising performance measure for restoration or indicator of carbon cycle processes in the Everglades and aquatic ecosystems worldwide.