Dissolved Organic Matter Characteristics Across a Subtropical Wetland’s Landscape: Application of Optical Properties in the Assessment of Environmental Dynamics
Wetlands are known to be important sources of dissolved organic matter (DOM) to rivers and coastal environments. However, the environmental dynamics of DOM within wetlands have not been well documented on large spatial scales. To better assess DOM dynamics within large wetlands, we determined high resolution spatial distributions of dissolved organic carbon (DOC) concentrations and DOM quality by excitation–emission matrix spectroscopy combined with parallel factor analysis (EEM–PARAFAC) in a subtropical freshwater wetland, the Everglades, Florida, USA. DOC concentrations decreased from north to south along the general water flow path and were linearly correlated with chloride concentration, a tracer of water derived from the Everglades Agricultural Area (EAA), suggesting that agricultural activities are directly or indirectly a major source of DOM in the Everglades. The optical properties of DOM, however, also changed successively along the water flow path from high molecular weight, peat-soil and highly oxidized agricultural soil-derived DOM to the north, to lower molecular weight, biologically produced DOM to the south. These results suggest that even though DOC concentration seems to be distributed conservatively, DOM sources and diagenetic processing can be dynamic throughout wetland landscapes. As such, EEM–PARAFAC clearly revealed that humic-enriched DOM from the EAA is gradually replaced by microbial- and plant-derived DOM along the general water flow path, while additional humic-like contributions are added from marsh soils. Results presented here indicate that both hydrology and primary productivity are important drivers controlling DOM dynamics in large wetlands. The biogeochemical processes controlling the DOM composition are complex and merit further investigation.
Keywordsdissolved organic matter dissolved organic carbon fluorescence characteristics excitation–emission matrix parallel factor analysis spatial distribution wetlands Everglades
- Findlay SEG, Sinsabaugh RL, Eds. 2003. Aquatic ecosystems: interactivity of dissolved organic matter. San Diego: Academic Press.Google Scholar
- Harvey JW, McCormick PV. 2009. Groundwater’s significance to changing hydrology, water chemistry, and biological communities of a floodplain ecosystem, Everglades, South Florida, USA. Hydrology Journal 17:185–201.Google Scholar
- Helms JR, Jason AS, Ritchie JD, Minor EC, Kieber DJ, Mopper K. 2008. Absorption spectral slopes and slope ratios as indicators of molecular weight, source, and photobleaching of chromophoric dissolved organic matter. Limnol Oceanogr 53:955–69.Google Scholar
- Larsen LG, Aiken GR, Harvey JW, Noe GB, Crimaldi JP. 2010. Using fluorescence spectroscopy to trace seasonal DOM dynamics, distribution effects, and hydrologic transport in the Florida Everglades. J Geophys Res 115:G03001. doi:10,1029/2009JG001140.
- Light SS, Dineen JW. 1994. Water control in the Everglades: a historical perspective. In: Davis SM, Ogden JC, Eds. Everglades: the ecosystem and its restoration. Delray Beach: St. Lucie Press. p 47–84.Google Scholar
- McCormick PV, Newman S, Miao SL, Gawlik DE, Marley D, Reddy KR, Fontaine TD. 2002. Effects of anthropogenic phosphorus inputs on the Everglades. In: Porter JW, Porter KG, Eds. The Everglades, Florida Bay, and coral reefs of the Florida Keys: an ecosystem sourcebook. Boca Raton: CRC Press. p 83–126.Google Scholar
- Mulholland PJ. 2003. Large-scale patterns in dissolved organic carbon concentration, flux, and sources. In: Findlay SEG, Sinsabaugh RL, Eds. Aquatic ecosystems: interactivity of dissolved organic matter. San Diego: Academic Press. p 139–59.Google Scholar
- Price RM, Swart PK. 2006. Geochemical indicators of groundwater recharge in the surficial aquifer system, Everglades National Park, Florida, USA. In: Harmon RS, Wicks C, Eds. Perspectives on Karst geomorphology, hydrology, and geochemistry. Geological Society of America Special Paper 404. Boulder, Colorado. p 251–66.Google Scholar
- Richardson CJ. 2009. The Everglades: North America’s subtropical wetland. Wetlands Ecol Manage. doi:10.1007/sl1273-009-9156-4.
- Scheidt DJ, Kalla PI. 2007. Everglades ecosystem assessment: water management and quality, eutrophication, mercury contamination, soils and habitat. Monitoring for adaptive management. A R-EMAP Status Report. USEPA Region 4, Athens GA. EPA 904-R-07-001. 98p.Google Scholar
- Spencer RGM, Pellerin BA, Bergamaschi BA, Downing BD, Kraus TEC, Smart DR, Dahlgren RA, Hernes PJ. 2007. Diurnal variability in riverine dissolved organic matter composition determined by in situ optical measurement in the San Joaquin River (California, USA). Hydrol Process 21:3181–9.CrossRefGoogle Scholar
- Spencer RGM, Aiken GR, Bulter KD, Dornblaser MM, Striegl RG, Hernes PJ. 2009a. Utilizing chromophoric dissolved organic matter measurements to derive export and reactivity of dissolved organic carbon exported to the Arctic Ocean: A case study of the Yukon River, Alaska. Geophys Res Lett 36:L06041.CrossRefGoogle Scholar
- Spencer RGM, Hernes PJ, Ruf R, Baker A, Dyda RY, Stubbins A, Six J. 2010. Temporal controls on dissolved organic matter and lignin biogeochemistry in a pristine tropical river, Democratic Republic of Congo. J Geophys Res 115:G03013. doi:10.1029/2009JG001180,2010.
- Stedmon CA, Bro R. 2008. Characterizing dissolved organic matter fluorescence with parallel factor analysis: a tutorial. Limnol Oceanogr Methods 6:572–9.Google Scholar
- Stober QJ, Thornton K, Jones R, Richards J, Ivey C, Welch R, Madden M, Trexler J, Gaiser E, Scheidt D, Rathburn S. 2001. South Florida ecosystem assessment: Phase I/II – Everglades stressor interactions: hydropatterns, eutrophication, habitat alteration, and mercury contamination. USEPA Region 4, Athens GA. EPA904-R-01-002. 63 pp.Google Scholar
- Tate RL. 1980. Microbial oxidation of histosols. Adv Microb Ecol 4:169–210.Google Scholar
- Yamashita Y, Jaffé R, Maie N, Tanoue E. 2008. Assessing the dynamics of dissolved organic matter (DOM) in coastal environments by excitation and emission matrix fluorescence and parallel factor analysis (EEM-PARAFAC). Limnol Oceanogr 53:1900–8.Google Scholar