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  1. Institute of Food and Agricultural Sciences (IFAS) Biogeochemistry of Wetlands Science and Applications June 23-26, 2008 Topic: Dissolved Organic Matter Wetland Biogeochemistry Laboratory Soil and Water Science Department University of Florida Instructor Todd Z. Osborne 4/2/2014 WBL

  2. Biogeochemistry of Wetlands Science and Applications Topic: Dissolved Organic Matter • Learning Objectives • Define dissolved organic matter [DOM]/ carbon • Define terminology / nomenclature • Explore components and characteristics of DOM • Explore sources and fate of DOM • Discuss ecological role of DOM in wetlands • Case study: DOM in Everglades WBL

  3. “Transformations of POM/DOM by bacteria and fungi are fundamental to the structure and dynamics of energy and nutrient fluxes in aquatic ecosystems.” - Robert G.Wetzel WBL

  4. Coarse Particulate Organic Matter (CPOM) Fine Particulate Organic Matter (FPOM) Ultra Fine Particulate Organic Matter (UPOM) Dissolved Organic Matter (DOM) Colloidal Dissolved Organic Matter (CDOM) >1 mm 1 mm – 250 um 250 um -0.45 um < 0.45 um 0.45 um-0.2 um Organic Matter Fractions DOM vs. DOC Note: historical operational definitions WBL

  5. Sources of DOM • Degradation products of primary production • Degradation products of Secondary/ tertiary production • By-products of bacterial / fungal / algal / plant / animal metabolic activity • Allochthanous organic matter • Autochthonous organic matter WBL

  6. Decay Continuum Live plant CO2 CH4 Plant standing dead Litter layer Surface peat DOM Buried peat WBL

  7. “Alphabet Soup” Proteins and amino acids Carbohydrates (mono +poly saccharides) Waxes and lipids Anthropogenic organics Humic and fulvic acids High and low molecular weight intermediates And many more……… WBL

  8. Anthropogenic Organics • Petroleum products (BTEX, MTBE) • Pesticides (DDT, DDE…..) • Herbicides (2,4D, Atrazine) • Industrial wastes (PCB’s, aromatics) WBL

  9. Acid insoluble / base soluble High Mol. Weight 10k – 150+K Da Highly unsaturated / aromatic Imparts color (brown) Acid and base soluble Medium to High Mol. Weights 3K-10K Da Moderately unsaturated Aromatic / aliphatic Imparts color (yellow) Humic and Fulvic Acids Humic Acids Fulvic Acids WBL

  10. Relative Composition of Humic and Fulvic Acids Element Humic Acid Fulvic Acid Carbon 53-59% 40-50% Oxygen 32-38% 40-50% Hydrogen 3-6% 4-7% Nitrogen 0.8-4% 0.9-3% Sulfur 0.1-1.5% 0.1-3.6% WBL

  11. Lignin Microbial utilization Phenolic aldehydes and acids Polyphenols Microbial utilization and oxidation Quinones Humic Acids Fulvic Acids Polyphenol Theory of Humic Formation Celluloseand other non-lignin substrates WBL

  12. Fate of DOM Biotic vs. Abiotic Mineralization Assimilation Photolysis Export Sedimentation WBL

  13. Photolysis • Photo induced oxidation • Photodegradation, Photodecomposition, Photolytic oxidation • Absorbance of high energy UV light by chromophores, conjugated double bonds • Energy has to go somewhere……. WBL

  14. Ecological Functions of DOM Energy, Energy, Energy Carbon Storage Source / sink of essential nutrients N&P Source / sink of metals and major cations Light attenuation Sorption of xenobiotics WBL

  15. Energy and the Food Web • 90-99% DOM consumed by bacteria and fungi • Microbial loop • Heterotrophy, chemo-organotrophy, photoheterotrophy WBL

  16. Storage Pools of Carbon [CO2] Plant Biomass C [CH4] Particulate Organic C [POC] Microbial Biomass C [MBC] Dissolved Organic C [DOC] Up to 95% utilizable carbon in system WBL

  17. Bacteria and Fungi • Utilize polymeric substrates by stepwise enzymatic depolymerization and hydrolosis • Utilize photolysis / photodegradation products of DOM • 50% growth utilizes DOM of 1K Da size • Passes energy up trophic levels via microbial loop • Very efficient WBL

  18. Microbial Loop FISH DOM Bacteriavores Bacteria

  19. Algae • Photoheterotrophy aka mixotrophy • Assimilate DOM during light and dark conditions (carbon dioxide availability) • Unlike bacteria, only use small MW compounds such as acetate, lactate, ethanol, and pyruvate WBL

  20. DOM as Source/ Sink for nutrients and important cations • Carbon, nitrogen, phosphorus • Cation exchange • pH buffering • Chelation of trace metals • Sequester toxics (Al & Hg!!) • Bind toxic organics (PAH,PCB) WBL

  21. DOM and Light Attenuation • Absorb UV light energy = protection of sensitive biota • Attenuate Photosyntheticly Active Radiation (PAR) • Decrease benthic or epiphytic algal primary productivity WBL

  22. DOM Around the World Site DOC mg/l Everglades, USA 35-40 Hubbard Brook, USA 2-3 Papyrus swamp, Uganda 85-107 Amazon River, Brazil 35-88 Wetland, Nova Scotia 52-68 Billabong, Australia 70-75 WBL

  23. WBL Osborne et al. unpublished data

  24. WBL

  25. WBL

  26. Particulate Organic Matter 1 Kg A Leachable DOC Export DOC Pool B C Bioavailable DOC Respiration Microbial Community D Biosynthesis E Microbial Biomass Fate of plant derived DOC in the Everglades All units are expressed as g C per kg of source plant biomass Osborne et al. unpublished data WBL

  27. DOM Cycle in Wetlands UV CO2 CO2 CH4 Decomposition/leaching Decomposition/leaching Litter Microbial biomass DOM HCO3- Export Import Peat Microbial biomass HCO3- CH4 DOM Decomposition leaching Decomposition/leaching WBL