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Lecture-7-Pdf Institute of Food and Agricultural Sciences (IFAS) Biogeochemistry of Wetlands SiScience an dAd App litilications Carbon Cycling Processes Wetland Biogeochemistry Laboratory Soil and Water Science Department University of Florida Instructor K. Ramesh Reddy [email protected] 6/22/20086/22/2008 WBL 1 1 Institute of Food and Agricultural Sciences (IFAS) Carbon Cycling Processes CO2 OM CH4 6/22/2008 WBL 2 1 Carbon Cycling Processes LtLecture OtliOutline Introduction Major components of carbon cycle Organic matter accumulation Characteristics of organic matter Decomposition processes Regulators of organic matter decomposition Greenhouse gases Summary 6/22/2008 WBL 3 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 6/22/2008 WBL 4 2 Oxidation States of Carbon [[]+4] [0] CO 2 C6H12O6 [-4] CH4 6/22/2008 WBL 5 Carbon Reservoirs [1014 kg] Atmospheric CO2 7 Biomass 4.8 Fresh water 2.5 Marine 5-8 Soil organic matter 30-50 6/22/2008 WBL 6 3 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) 6/22/2008 WBL 7 Detrital Plant Biomass Grazers CO2 microorganisms Aerobic Detritus Decomposition Peat Water table Water Burial Anaerobic Compaction 6/22/2008 WBL 8 4 Carbon Cycle UV CO2 CO2 CH4 Decomposition/leaching Decomposition/leaching - Litter Microbial DOC HCO3 Import biomass Export - Peat Microbial DOC HCO3 Decomposition biomass CH4 leaching Decomposition/leaching 6/22/2008 WBL 9 Organic Matter ¾ Storages ¾ Outputs ¾ Soil organic matter ¾ Greenhouse gases ¾ Plant detritus/litter ¾ Nutrient export ¾ Dissolved organic matter ¾ Ecological/Environment ¾ Microbial biomass al Significance ¾ Transformations ¾ Carbon sequestration ¾ Microbial respiration ¾ MthMethanogenes is ¾ Global warming ¾ Water quality ¾ Ecosystem productivity 6/22/2008 WBL 10 5 Net Primary Productivity 2 [g/m - 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 6/22/2008 WBL 11 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 6/22/2008 WBL 12 6 Organic Matter Accumulation 0 Organic matter accumulation 10 1964 marker Soil Depth [cm] 20 Cs-137 Activity 6/22/2008 WBL 13 A. Detritus attached to plant B. Detritus detached from plant C. Decomposed Water detritus from detritus previous year Soil D. Organic matter and nutrient accretion Plant Soil Organic Detritus A B C Matter Decay continuum 6/22/2008 WBL 14 7 Decay Continuum Live plant CO 2 CH4 Plant standing dead Litter layer Surface peat Microbial decomposers Buried peat 6/22/2008 WBL 15 Carbon Accumulation in Wetlands Potential energy source (reduced carbon, electron donor Long-term storage of nutrients, heavy metals,,gp and toxic organic compounds Major component of global carbon cycles 6/22/2008 WBL 16 8 Carbon Forms Particulate orgg()anic carbon (POC) Microbial biomass carbon (MBC) Dissolved organic carbon (DOC) Dissolved inorganic carbon (DIC) CO2 + H2O = H2CO3 - + H2CO3 = HCO3 + H - 2- + HCO3 = CO3 + H 6/22/2008 WBL 17 Chemical constituents of organic matter Non Humic compounds: Carbohydrates (Simple sugars) Monosaccharides: glucose. Polysaccharides: Starch, Cellulose, and Hemicellulose Proteins Lipids etc Phenolic compounds: Lign in (branc he d ran dom po lymer o f p heny l propano id un it ) Tannins (heterogeneous groups of phenolic compounds) 6/22/2008 WBL 18 9 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%] 6/22/2008 WBL 19 Cellulose β-D-glucosidic bond H OH CH OH CH2OH 2 H O H H O O H H H H OH H OH O OH H H H O H OH OH H CH2OH H 6/22/2008 WBL 20 10 Lignin 6/22/2008 WBL 21 Soil Organic Matter [SOM] SOM Extract with Alkali [alkali-soluble] Humin Treat with Acid [alkali-insoluble] Humic Acid Fulvic Acid [acid-insoluble] [acid-soluble] 6/22/2008 WBL 22 11 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. 6/22/2008 WBL 23 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. 6/22/2008 WBL 24 12 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 6/22/2008 WBL 25 Microbial Biomass 6/22/2008 WBL 26 13 Microorganisms [Percent wet weight] • 70% water Total weight of • Macromolecules actively growing cell • 15% protein of Escherichia coli • 3% polysaccharide • 2% lipids Wet wt = 9.5 x 10-13 g • 5% RNA Dt2810Dry wt = 2.8 x 10-13 g • 1 % DNA • 1 % Inorganic ions • 3 % others 6/22/2008 WBL 27 Microbial Decomposers Typically 1-5% of total C mass in soil PtfthttProcess most of the ecosystem net production Principal transformers of organic carbon Recycle carbon and nutrients in recalcitrant biopolymers Regulate energy flow and nutrient retention 6/22/2008 WBL 28 14 Techniques to Measure MICROBIAL BIOMASS Direc t ce ll coun t : a bun dance Lipid based : live microbial biomass CHCl3 Fumigation-extraction based: estimate of Carbon Metabolic activity based: Enzyme activities 6/22/2008 WBL 29 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) 6/22/2008 WBL 30 15 MICROBIAL BIOMASS [Site = WCA-2A - Everglades] 10 9 8 7 6 LITTER 5 0-10 cm 4 3 10-30 cm 2 1 0 0246810 Distance from Inflow, km 6/22/2008 WBL 31 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 43x104.3 x 105 <30x10< 3.0 x 103 Formate 2.3 x 105 < 3.0 x 103 Hector et al. 2003 6/22/2008 WBL 32 16 Detrital Matter Leaching Complex Polymers Cellulose; Hemicellulose; Lignin Proteins; Lipids and waxes End product Monomers Electron Sugars;Amino acids Bacterial acceptors Fatty acids Cell End products 6/22/2008 WBL 33 + energy Extracellular Enzymes 6/22/2008 WBL 34 17 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 space periplasmic (ectoenzyme) Bacterial cell (Chrost,1990) – Enzyme occurs free in the water or adsorbed to surface other than its producers e.g., detrital particles or clay Detrital/clay material material (extracellular enzyme) •Most of these are hydrolases 6/22/2008 WBL 35 Enzymes • Cellulose degradation – Exocellulase - Cellulose – B-glucosidase - Cellobiose • Hemicellulose degradation – Exoxylanase - Xylan – B-xylosidase - Xylobiose • Lignin degradation – Phenol oxidase - Lignin and Phenols 6/22/2008 WBL 36 18 Enzyme – Catalyzed Reaction E + S E S E + P S = Substrate E = Enzyme P = Product All enzymes are proteins – amino acid polymers 6/22/2008 WBL 37 Reactions of Enzymes 2- 2- R-O-PO3 + H2O R-OH + HO-PO3 alkaline phosphatase - + 2- R-O-SO3 + H2O R-OH + H + SO4 arylsulfatase R-O-glucose + H2O R-OH + glucose β-glucosidase casein + H2O tyrosine protease phenolics + O2 quinones phenol oxidase 6/22/2008 WBL 38 19 Inhibition of enzyme activity Humic acid-Enzyme complex Humic acid Active Enzyme + E E 2+ 2+ 2+ Ca Ca Ca Ca2+ Ca2+ + E Ca2+ + E Ca2+ Ca2+ Ca2+ 6/22/2008 WBL 39 Measurement of Enzymes • Spectroscopic – p-nitrop heno l p hosp hate (p NPP) • Fluorescence – Methylumbelliferyl phosphate (MUF) – Enzyme Labeled Fluorescence (ELF) APase P P MUF-P MUF Pi 6/22/2008 WBL 40 20 β Glucosidase Activity -1 h -1 100 50 -nitrophenol g p 0 g u Oxygen Nitrate Sulfate Bicarbonate E h (mV) 618 214 -145 -217 pH 4.5 7.6 7.5 6.5 6/22/2008 WBL 41 β Glucosidase Activity [Everglades --WCAWCA--2A]2A] 4 impacted ) February transitional -1 2 ity unimpacted h v 1 - 0 4 May 2 nitrophenol g nitrophenol 0 p- -Glucosidase Acti 4 g AtAugust D - (m B 2 0 Detritus 0-10 cm 10-30 cm 6/22/2008Wright and Reddy, 2001 WBL 42 21 Pheno oxidase Activity [Everglades --WCAWCA--2A]2A] 5 Wright and Reddy, 2001 ) 4 y 1 May - t 3 min 2 -1 1 0 5 August impacted 4 transitional le [DQC]g ol Oxidase Activi ol Oxidase unimpacted o 3 n 2 (um Phe 1 0 Detritus 0-10 cm 10-30 cm DQC = dihydroindole quinone carboxylate 6/22/2008 WBL 43 Microbial Activity 6/22/2008 WBL 44 22 Detrital Matter Leaching Complex Polymers Cellulose; Hemicellulose; Lignin Proteins; Lipids and waxes Reduced product Monomers Electron Sugars;Amino acids Bacterial acceptors Fatty acids Cell End products 6/22/2008 WBL 45 + energy Organic Matter Decomposition IL DEPTH IL SO Decreasing energy yield 6/22/2008 WBL 46 23 Metabolism • Catabolism • Anabolism • Types of energy source • Light … Phototrophs • Inorganic … Lithotrophs • Organic ….
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