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Wetland Biogeochemistry Science: Carbon Cycling Processes and Applications

Learn about major components of the carbon cycle, organic matter accumulation, decomposition processes, regulators, greenhouse gases, and more. Understand the global significance of the carbon cycle, biogeochemical controls, and storage in soil and water. Explore carbon reservoirs, soil organic matter, detrital biomass, microbial processes, and ecological significance. Discover carbon accumulation in wetlands and different forms of organic matter. Gain insights into the chemical constituents of organic matter and soil organic matter fractions. Dive into the decay continuum, carbon forms, and the available carbon pool. Enhance your understanding of wetland biogeochemistry with this comprehensive course.

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Wetland Biogeochemistry Science: Carbon Cycling Processes and Applications

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  1. Institute of Food and Agricultural Sciences (IFAS) Biogeochemistry of Wetlands Science and Applications Carbon Cycling Processes Wetland Biogeochemistry Laboratory Soil and Water Science Department University of Florida Instructor K. Ramesh Reddy krr@ufl.edu 10/29/2019 1 WBL

  2. Institute of Food and Agricultural Sciences (IFAS) Carbon Cycling Processes CO2 OM CH4 WBL

  3. Carbon Cycling Processes • Lecture Outline • Introduction • Major components of carbon cycle • Organic matter accumulation • Characteristics of organic matter • Decomposition processes • Regulators of organic matter decomposition • Greenhouse gases • Summary WBL

  4. Carbon Cycling Processes • Learning Objectives • Describe major components of carbon cycle • Develop an understanding of the chemical composition of plant litter and soil organic matter • Long-term accumulation of organic matter • Describe the role of enzymes and microbial communities involved in decomposition • Determine organic matter turnover • Indentify the role biogeochemical controls and regulators • Understand the global significance of carbon cycle • Draw a carbon cycle and identify storages and fluxes within and between soil and water column WBL

  5. Oxidation States of Carbon [+4] [0] CO2 C6H12O6 [-4] CH4 WBL

  6. Carbon Reservoirs[1014 kg] • Atmospheric CO2 7 • Biomass 4.8 • Fresh water 2.5 • Marine 5-8 • Soil organic matter 30-50 WBL

  7. Soil Organic Matter [SOM] • Undecayed plant and animal tissues • Partially decomposed material • Soil biomass • Sources of SOM • External: Particulate (inputs) • Internal: detrital material (macrophytes, algal mats, roots) WBL

  8. Detrital Plant Biomass Aerobic Detritus Decomposition Water table Peat Burial Anaerobic Compaction Grazers CO2 microorganisms WBL

  9. Carbon Cycle UV CO2 CO2 CH4 Decomposition/leaching Decomposition/leaching Litter Microbial biomass HCO3- DOC Export Import Peat Microbial biomass HCO3- CH4 DOC Decomposition leaching Decomposition/leaching WBL

  10. Storages Soil organic matter Plant detritus/litter Dissolved organic matter Microbial biomass Transformations Microbial respiration Methanogenesis Outputs Greenhouse gases Nutrient export Ecological/Environmental Significance Carbon sequestration Global warming Water quality Ecosystem productivity Organic Matter WBL

  11. Net Primary Productivity[g/m2 - year] [Craft, 2001] Bog 380-800 Marsh 500 -1100 Riverine 400-1150 Fresh tidal 500-1600 Brackish 600-1600 Salt 950-2000 Mangroves 600-1200 WBL

  12. Carbon Accumulation in Wetlands[g C/m2 year] Alaska - Sphagnum 11-61 Finland - Sphagnum - Carex 20-28 Ontario - Sphagnum bog 30-32 Georgia - Taxodium 23 Florida - Cladium 70-105 WBL

  13. Organic Matter Accumulation 0 Organic matter accumulation 10 Soil Depth [cm] 1964 marker 20 Cs-137 Activity WBL

  14. A. Detritus attached to plant B. Detritus detached from plant C. Decomposed detritus from previous year Water detritus D. Organic matter and nutrient accretion Soil Soil Organic Matter Plant Detritus A B C Decay continuum WBL

  15. Decay Continuum Live plant CO2 CH4 Plant standing dead Litter layer Microbial decomposers Surface peat Buried peat WBL

  16. Carbon Accumulation in Wetlands • Potential energy source (reduced carbon, electron donor • Long-term storage of nutrients, heavy metals, and toxic organic compounds • Major component of global carbon cycles WBL

  17. Carbon Forms • Particulate organic carbon (POC) • Microbial biomass carbon (MBC) • Dissolved organic carbon (DOC) • Dissolved inorganic carbon (DIC) • CO2 + H2O = H2CO3 • H2CO3 = HCO3- + H+ • HCO3- = CO32- + H+ WBL

  18. Chemical constituents of organic matter • Non Humic compounds: • Carbohydrates (Simple sugars) • Monosaccharides: glucose. • Polysaccharides: Starch, Cellulose, and Hemicellulose • Proteins • Lipids etc • Phenolic compounds: • Lignin (branched random polymer of phenyl propanoid unit) • Tannins (heterogeneous groups of phenolic compounds) WBL

  19. Organic Matter (Plant and Soil) • Water soluble components [<10%] • Sugars, amino acids and fatty acids • Cellulose [15-60%] • Hemicellulose [10-30%] • Lignin [5-30%] • Proteins [2-15%] • Lipids and Waxes [1-8%] • Ash (mineral) [1-13%] WBL

  20. Cellulose b-D-glucosidic bond OH H CH2OH CH2OH O O H H H O H H H H H OH H OH OH O H H H O OH OH CH2OH H H WBL

  21. Lignin WBL

  22. Soil Organic Matter [SOM] SOM Extract with Alkali [alkali-soluble] Humin [alkali-insoluble] Treat with Acid Humic Acid [acid-insoluble] Fulvic Acid [acid-soluble] WBL

  23. Fulvic Acid • More ‘O’ and less ‘C’. • MW 1000 -30,000. • Less advanced stage of decomposition. • More COOH group per unit mass. • Functional group acidity (11.2 mol/kg). • Alkali and acid soluble. WBL

  24. Humic Acid • More ‘C’ and less ‘O’. • MW 10,000 -100,000. • Advanced stage of decomposition. • Less COOH group per unit mass. • Functional group acidity (6.7 mol/kg). • Alkali soluble. WBL

  25. Available Carbon Pool • Represents small but biologically active fraction of DOC • Immediately available for microbial utilization • Extremely small in C-limited system • Rapid turnover • May not be directly measurable • Affects short-term community metabolism WBL

  26. Microbial Biomass WBL

  27. 70% water Macromolecules 15% protein 3% polysaccharide 2% lipids 5% RNA 1 % DNA 1 % Inorganic ions 3 % others Total weight of actively growing cell of Escherichia coli Wet wt = 9.5 x 10-13 g Dry wt = 2.8 x 10-13 g Microorganisms[Percent wet weight] WBL

  28. Microbial Decomposers • Typically 1-5% of total C mass in soil • Process most of the ecosystem net production • Principal transformers of organic carbon • Recycle carbon and nutrients in recalcitrant biopolymers • Regulate energy flow and nutrient retention WBL

  29. Techniques to Measure MICROBIAL BIOMASS Direct cell count : abundance Lipid based : live microbial biomass CHCl3 Fumigation-extraction based: estimate of Carbon Metabolic activity based: Enzyme activities WBL

  30. MICROBIAL COMMUNITY STRUCTURE • Pure culture approach • Microscopy • Community level physiological profile (CLPP): Substrate utilization: BIOLOG • Measurement of cellular component (physiological status, functional groups):PLFA • Methods based on nucleic acids analysis (abundance, diversity and phylogeny of organisms): gene specific analysis (16S rDNA, DGGE, TGGE, Trflp) WBL

  31. MICROBIAL BIOMASS [Site = WCA-2A - Everglades] 10 9 8 7 LITTER 6 % of Total Carbon 0-10 cm 5 4 3 10-30 cm 2 1 0 0 2 4 6 8 10 Distance from Inflow, km WBL

  32. MICROBIAL NUMBERS [MPN/g soil] [Site = WCA-2A - Everglades] Substrate Eutrophic Oligotrophic Lactate 9.3 x 105 9.2 x 103 Acetate 2.3 x 105 3.6 x 103 Propionate 4.3 x 105 9.2 x 103 Butyrate 4.3 x 105 < 3.0 x 103 Formate 2.3 x 105 < 3.0 x 103 Hector et al. 2003 WBL

  33. DetritalMatter Leaching Complex Polymers Cellulose; Hemicellulose; Lignin Proteins; Lipids and waxes Extracellular Enzyme (Hydrolysis) End product Monomers Sugars;Amino acids Fatty acids Electron acceptors Bacterial Cell End products + energy WBL

  34. Extracellular Enzymes WBL

  35. Periplasmic space Bacterial cell Detrital/clay material Extracellular Enzymes • An extracellular enzyme is involved in transformation or degradation of polymeric substances external to cell membrane. • Enzyme can be bound to the cell membrane or are periplasmic (ectoenzyme)(Chrost,1990) • Enzyme occurs free in the water or adsorbed to surface other than its producers e.g., detrital particles or clay material (extracellular enzyme) • Most of these are hydrolases WBL

  36. Enzymes • Cellulose degradation • Exocellulase - Cellulose • B-glucosidase - Cellobiose • Hemicellulose degradation • Exoxylanase - Xylan • B-xylosidase - Xylobiose • Lignin degradation • Phenol oxidase - Lignin and Phenols WBL

  37. Enzyme – Catalyzed Reaction E S E + P E + S S = Substrate E = Enzyme P = Product All enzymes are proteins – amino acid polymers WBL

  38. Reactions of Enzymes R-O-PO32- + H2O R-OH + HO-PO32- alkaline phosphatase R-O-SO3- + H2O R-OH + H+ + SO42- arylsulfatase R-O-glucose + H2O R-OH + glucose b-glucosidase casein + H2O tyrosine protease phenolics + O2 quinones phenol oxidase WBL

  39. Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Inhibition of enzyme activity Humic acid-Enzyme complex Active Enzyme Humic acid E E + Ca2+ + E + E WBL

  40. P APase MUF-P P MUF Pi Measurement of Enzymes • Spectroscopic • p-nitrophenol phosphate (pNPP) • Fluorescence • Methylumbelliferyl phosphate (MUF) • Enzyme Labeled Fluorescence (ELF) WBL

  41. b Glucosidase Activity 100 ug p-nitrophenol g-1 h-1 50 0 Oxygen Nitrate Sulfate Bicarbonate E h (mV) 618 214 -145 -217 pH 4.5 7.6 7.5 6.5 WBL

  42. impacted transitional unimpacted b Glucosidase Activity [Everglades -WCA-2A] 4 February 2 0 4 May B-D-Glucosidase Activity (mg p- nitrophenol g-1 h-1) 2 0 4 August 2 0 Detritus 0-10 cm 10-30 cm WBL Wright and Reddy, 2001

  43. impacted transitional unimpacted Phenooxidase Activity [Everglades -WCA-2A] Wright and Reddy, 2001 5 4 May 3 2 1 0 Phenol Oxidase Activity (umole [DQC]g-1 min-1) 5 August 4 3 2 1 0 Detritus 0-10 cm 10-30 cm DQC = dihydroindole quinone carboxylate WBL

  44. Microbial Activity WBL

  45. DetritalMatter Leaching Complex Polymers Cellulose; Hemicellulose; Lignin Proteins; Lipids and waxes Extracellular Enzyme (Hydrolysis) Reduced product Monomers Sugars;Amino acids Fatty acids Electron acceptors Bacterial Cell End products + energy WBL

  46. Decreasing energy yield Organic Matter Decomposition SOIL DEPTH WBL

  47. Metabolism • Catabolism • Anabolism • Types of energy source • Light … Phototrophs • Inorganic … Lithotrophs • Organic …. Heterotrophs • Oxidation of organic compounds • Fermentation • Respiration WBL

  48. Chemolithotrophy • Inorganic compound as energy source • eg. H2S, Hydrogen gas, Fe(II), and NH3 • Source of carbon for biosynthesis cannot be organic therefore use CO2 and hence are autotrophs • Hydrogen oxidation • Sulfur oxidation • Ferrous iron oxidation • Annamox • Nitrification WBL

  49. Carbon CO2 H2O ADP hu 1/2O2 ATP (CH2O)n Phototrophy • Photosynthesis is conversion of light energy into chemical energy. • Most phototrophs are autotrophs ( use CO2 as sole Carbon source). OXYGENIC PHOTOTROPHS ANOXYGENIC PHOTOTROPHS Carbon CO2 H2S ADP S0 hu SO42- ATP (CH2O)n WBL

  50. Catabolism Energy sources: Organic, inorganic, light Waste products: Organic, inorganic Cell biomass Nutrients: N, P, K, S, Fe, Mg, ... Carbon sources: Organic, CO2 Anabolism Metabolism WBL

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