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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

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“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