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Biogeochemistry of WetlandsS i d A li tiS i d A li ti
Institute of Food and Agricultural Sciences (IFAS)
Science and ApplicationsScience and ApplicationsJune 23June 23--26, 200826, 2008
Wetland Biogeochemistry LaboratorySoil and Water Science Department
Topic: Dissolved Organic Matter
6/22/2008 WBL
InstructorTodd Z. Osborne
Soil and Water Science DepartmentUniversity of Florida
6/22/2008 1
Biogeochemistry of WetlandsScience and ApplicationsScience and Applications
Topic: Dissolved Organic Matter
Learning Objectives
Define dissolved organic matter [DOM]/ carbon Define terminology / nomenclature Explore components and characteristics of DOM
WBL
p pExplore sources and fate of DOM Discuss ecological role of DOM in wetlandsCase study: DOM in Everglades
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“Transformations of POM/DOM by bacteria and fungi are fundamental to the structure and dynamics of energy and nutrient fluxes in aquatic ecosystems.”ecosystems.
- Robert G.Wetzel
6/22/2008 3WBL
Organic Matter FractionsDOM vs. DOC
Coarse Particulate Organic Matter (CPOM)
Fine Particulate Organic Matter (FPOM)
Ultra Fine Particulate Organic Matter (UPOM)
>1 mm
1 mm – 250 um
250 um -0.45 um
Note: historical operational definitions
Dissolved Organic Matter (DOM)
Colloidal Dissolved Organic Matter (CDOM)
< 0.45 um
0.45 um-0.2 um
6/22/2008 4WBL
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Sources of DOM• Degradation products of primary
productionproduction• Degradation products of Secondary/
tertiary production• By-products of bacterial / fungal / algal /
plant / animal metabolic activity• Allochthanous organic matter• Allochthanous organic matter• Autochthonous organic matter
6/22/2008 5WBL
Live plant
Decay ContinuumDecay Continuum
CO CHPlant standing dead
Litter layer
CO2 CH4
Surface peat
Buried peat
DOM
6/22/2008 6WBL
4
“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………6/22/2008 7WBL
Anthropogenic Organics
• Petroleum products (BTEX, MTBE)• Pesticides (DDT, DDE…..)• Herbicides (2,4D, Atrazine)• Industrial wastes (PCB’s, aromatics)
6/22/2008 8WBL
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Humic and Fulvic Acids
Humic Acids Fulvic Acids
• Acid insoluble / base soluble
• High Mol. Weight• 10k – 150+K Da
• Acid and base soluble• Medium to High Mol.
Weights• 3K-10K Da
Humic Acids Fulvic Acids
• Highly unsaturated / aromatic
• Imparts color (brown)
• Moderately unsaturated• Aromatic / aliphatic• Imparts color (yellow)
6/22/2008 9WBL
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%Nit 0 8 4% 0 9 3%Nitrogen 0.8-4% 0.9-3%Sulfur 0.1-1.5% 0.1-3.6%
6/22/2008 10WBL
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Polyphenol Theory of Humic Formation
Cellulose and other non-lignin substrates
Lignin
Phenolic aldehydes and acids
Microbial utilization and oxidation
Polyphenols
Microbial utilization
and oxidation
Quinones
Humic Acids Fulvic Acids6/22/2008 11WBL
Fate of DOM
Mineralization
A i il ti
Photolysis
E tSedimentation
Biotic vs. Abiotic
Assimilation Export
6/22/2008 12WBL
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Photolysis
• Photo induced oxidationPhoto induced oxidation• Photodegradation,
Photodecomposition, Photolytic oxidation
• Absorbance of high energy UV light by chromophores conjugatedby chromophores, conjugated double bonds
• Energy has to go somewhere…….
6/22/2008 13WBL
Ecological Functions of DOM
E E EEnergy, Energy, Energy
Carbon Storage
Source / sink of essential nutrients N&P
Source / sink of metals and major cations
Light attenuation
Sorption of xenobiotics6/22/2008 14WBL
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Energy and the Food Web
• 90-99% DOM consumed by bacteria and fungi
• Microbial loop• Heterotrophy, chemo-organotrophy,
photoheterotrophy
6/22/2008 15WBL
Plant Biomass C [CO2]
Storage Pools of Carbon Storage Pools of Carbon
ParticulateOrganic C [POC]
MicrobialBiomass C [MBC]
[CH4]
DissolvedOrganic C [DOC]
Up to 95% utilizable carbon in system6/22/2008
16WBL
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Bacteria and Fungi• Utilize polymeric substrates by stepwiseUtilize 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
6/22/2008 17WBL
Microbial Loop
FISH
DOM
FISH
Bacteriavores
Bacteria
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Algae
• Photoheterotrophy aka mixotrophy• Assimilate DOM during light and dark
conditions (carbon dioxide availability)• Unlike bacteria, only use small MW
compounds such as acetate lactatecompounds such as acetate, lactate, ethanol, and pyruvate
6/22/2008 19WBL
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)
6/22/2008 20WBL
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DOM and Light Attenuation
• Absorb UV light energy = protection• Absorb UV light energy = protection of sensitive biota
• Attenuate Photosyntheticly Active Radiation (PAR)
• Decrease benthic or epiphytic algal ec ease be t c o ep p yt c a gaprimary productivity
6/22/2008 21WBL
DOM Around the World
Site DOC mg/lSite DOC mg/lEverglades, USA 35-40
Hubbard Brook, USA 2-3
Papyrus swamp, Uganda 85-107
Amazon River, Brazil 35-88Amazon River, Brazil 35 88
Wetland, Nova Scotia 52-68
Billabong, Australia 70-75
6/22/2008 22WBL
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Osborne et al. unpublished data6/22/2008 23WBL
6/22/2008 24WBL
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6/22/2008 25WBL
Species
Potentially Leachable Carbon (A)
Bioavailable DOC (C)
Microbial Biomass Production (E)
Microbial Respiration (D)
Export (B) A
Particulate Organic Matter1 Kg
Leachable DOC
Fate of plant derived DOC in the Everglades
Eleo 40.2 27.7 5.0 22.7 12.6
Typ 34.3 19.6 8.9 10.7 14.6 Clad 21.5 15.1 5.0 10.1 6.4 Spar 38.4 29.3 3.9 25.5 9.0
Thal 87.4 52.8 19.7 33.1 34.6
Nuph 179 97.9 20.3 77.6 81.6
Nym 220 153 38.3 115 66.3 Pan 48.2 27.2 3.9 23.3 21.0 T 105 67 6 8 1 59 6 37 7
D
C
BDOC Pool
Export
Respiration
Bioavailable DOC
Microbial Community
Tax 105 67.6 8.1 59.6 37.7 EBiosynthesis
Microbial Biomass
All units are expressed as g C per kg of source plant biomass
Osborne et al. unpublished data
6/22/2008 26WBL
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DOM Cycle in WetlandsDOM Cycle in Wetlands
CO
UV
Litter Microbialbiomass
DOM HCO3-
CO2CO2
Decomposition/leaching
Decomposition/leaching
CH4
Import Export
Peat Microbialbiomass
DOM HCO3-
CH4
Decomposition/leaching
Decompositionleaching
6/22/2008 27WBL