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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 .
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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
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
“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
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
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
Decay Continuum Live plant CO2 CH4 Plant standing dead Litter layer Surface peat DOM Buried peat WBL
“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
Anthropogenic Organics • Petroleum products (BTEX, MTBE) • Pesticides (DDT, DDE…..) • Herbicides (2,4D, Atrazine) • Industrial wastes (PCB’s, aromatics) WBL
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
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
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
Fate of DOM Biotic vs. Abiotic Mineralization Assimilation Photolysis Export Sedimentation WBL
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
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
Energy and the Food Web • 90-99% DOM consumed by bacteria and fungi • Microbial loop • Heterotrophy, chemo-organotrophy, photoheterotrophy WBL
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
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
Microbial Loop FISH DOM Bacteriavores Bacteria
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
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
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
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
WBL Osborne et al. unpublished data
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
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