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Organisms and their environment, including other organisms Ecology investigates: Resource colonization Resource decomposition and distribution Competition Succession Reproduction and development Production 6CO2 + 6H20 C6H1206 + 6O2 Decomposition C6H1206 + 6O2 6CO2 + 6H20 Energy = carbon (C) Ultimately measured in kilocalories/calories Nutrients = nitrogen (N) phosphorus (P) potassium (K) magnesium (Mg) Several other elements and compounds Autotroph Acquires energy through photosynthesis Plants, algae Heterotroph zymogenous autochthonous Acquires energy through eating Humans, mammals, birds, bacteria, fungi, insects, etc. Can be viewed from two perspectives: 1. Taxonomy: what is doing the decomposing? 2. Taphonomy: what processes are taking place? Most decomposition is biologically mediated (minimum 80%) Microorganisms (bacteria, fungi) Insects (flies, beetles) Scavengers Catalysis—enzymatic and chemical reactions transforming complex to simple. Comminution—physical breakdown of resource. Leaching—soluble material moved by water Resource Quality Decomposer Community Physicochemical environment Physicochemical Environment Four primary modulators of decomposition: Moisture Temperature Aeration (oxygen, carbon dioxide) pH A high quality resource An ephemeral resource patch/disturbance A source of water A habitat for microorganisms carbon:nitrogen Wood 145:1 Straw 100:1 Leaf litter 50:1 Manure 25:1 Stages of Decomposition 1. Fresh 2. Bloated 3. Active Decay 4. Advanced Decay 5. Skeleton In reality: Stages do not exist Stage characteristics can blend from one stage into another Stages provide a convenient means for taphonomists to assess decomposition • Autolysis starts: abiotic breakdown of cells and tissues • Associated with start of mortis triad • Little release of fluids and disturbance of surroundings • Flies first colonize: looking for place to lay eggs. • If too cold: microbes and scavengers dominate • If outside: vegetation and soil surface covered. The mortis triad Algor mortis—body temperature changes to ambient temperature Rigor mortis—temporary stiffening of the joints Livor mortis—settling and pooling of blood; blood will become “fixed” after a period of time. Gunn (2009) Gunn (2009) Fresh Stage (biological changes) Initial insect colonization (response to chemical disturbance, i.e. presence of corpse) Release of ammonia, sulphuric acid, carbon dioxide, nitrogen Increased microbial activity (response to physical disturbance) Initial shift in bacterial and fungal community structure (response to physical disturbance) Fresh Stage (chemical changes) • Increase in atmospheric • carbon dioxide (CO2) • methane (CH4) • hydrogen sulfide (H2S) • nitrogen (N2) • ammonia (NH3) Increase in gravesoil • ammonium (NH4+) • nitrate (NO3-) • phosphorus (P) • soil pH Bloat Stage Decomposition • Enteric microbial community produces gases (putrefaction) • Purge fluids released from orifices: mouth, nose, anus, etc. • Buildup of gas can cause rupturing, fluids released from ruptures in skin. • Fly larvae (maggots) are active Gunn (2009) Bloated (biological changes) Maggot activity Elevated microbial activity (CO2 respiration) Shift in bacterial community structure Bloated (chemical changes) Increased in gravesoil: ammonium calcium chloride fatty acids (butyric, propionic, valeric) magnesium organic N, ammonium, nitrate phosphorus potassium sodium sulphate Active Decay • Maggot activity at its peak • Increased release of fluids • Increased marbling, slippage of skin • Exposure of internal organs Active Decay (biological changes) Peak insect activity Death of associated vegetation (not sure why) Elevated microbial activity Shift in bacterial community structure Active Decay (chemical changes) Same elevated concentrations as observed in the bloated stage. Increased: Lipid phosphorus Enzyme activity Protease activity Phosphodiesterase activity Total nitrogen Total phosphorus Advanced Decay (biological changes) Maggots have migrated. Corpse comprises skin, organs, hair and bone. Declining microbial biomass and activity, but still greater than non-gravesoil. Fruiting of postputrefaction fungi. Shift in bacterial community structure. Advanced Decay (chemical changes) Same as observed during bloated and active decay. Postputrefaction fungus • Skeleton Stage Decomposition Can persist from weeks to millenia • Materials present: bone, teeth, hair, dried skin Gunn (2009) Gunn (2009) Time Fresh Gravesoil Biology Gravesoil Chemistry Bloated Active Decay Advanced Decay Skeleton •Increased microbial activity, biomass •Succession of fungi from early phase to late phase •Shift in bacterial community •Increased amino acids, nitrate, ninhydrinreactive nitrogen, total nitrogen, total phosphorus •Decreased pH •Initial disturbance •Increased microbial activity •Shift in bacterial and fungal community structure •Increased microbial activity •Shift in bacterial community structure •Increased microbial activity, biomass •Shift in bacterial community structure •Declining microbial activity and biomass •early phase postputrefactio n fungi •Shift in bacterial community structure •Initial disturbance •Increased ammonium, carbon dioxide, nitrate, phosphate •Increased ammonium, butyric acid, calcium, chloride, magnesium, ninhydrinreactive N, nitrate, potassium, phosphate, propionic acid, sodium, sulphate, valeric acid •Increased pH •See Bloated •Increased lipid phosphorus, protease activity, phosphodiester ase activity, total nitrogen, total phosphorus •See Bloated •Increased ammonium, electrical conductivity, ninhydrinreactive nitrogen, lipid phosphorus, total nitrogen, total phosphorus Gunn A (2009) Essential Forensic Biology. WileyBlackwell. Hopkins DW (2008) The role of soil organisms in terrestrial decomposition. In: Tibbett M, Carter DO; Soil Analysis in Forensic Taphonomy. CRC Press: 53-66.