Biogeochemical

• Biogeochemical cycles

  Nutrient cycles in ecosystems that involve biotic (biosphere) and abiotic (geosphere) components
• Elements that cycle globally in the atmosphere

  • Gaseous carbon
  • Oxygen
  • Sulfur
  • Nitrogen
  • Water
• Elements that cycle locally in terrestrial systems but more broadly when dissolved in aquatic systems

  • Phosphorus
  • Potassium
  • Calcium
• Food webs

  Living organisms are in the available organic compartment, and whenever heterotrophs (consumers) consume food, they recycle nutrients within that reservoir
• Assimilation & photosynthesis

  1. Producers acquire nutrients molecules and ions from the atmosphere (air), soil, and water of the available inorganic compartment

  2. Consumers acquire nutrients from the available inorganic compartment when they drink water or absorb mineral ions through the body surface
• Excretion & respiration

  Transfer nutrients from organisms to the available inorganic compartment
• Sedimentation


  Converts available inorganic ions and particles into unavailable inorganic rocks
• Weathering and erosion

  Materials reenter the available inorganic compartment when rocks are uplifted and eroded or weathered
• Waterlogging and fossilisation


  Some available organic remains are converted into coal, oil, and peat (fossil fuels) - in the unavailable organic compartment
• Fossil fuels


  Unavailable organic materials (e.g., coal, oil, etc.) formed from the waterlogging, death, compaction, and fossilisation of organic matter
• Unavailable inorganic


  Rocks & minerals formed from the sedimentation, weathering, and erosion of available inorganic materials
• The Water Cycle


  1. Evaporation

  2. Transpiration

  3. Condensation

  4. Precipitation

  5. Surface and groundwater
• Carbon-based organic molecules


  Essential to all organisms (e.g., Glucose [C6H12O6], Sucrose [C12H22O11])
• Photosynthesis


  Photosynthetic organisms convert CO2 to organic molecules (e.g., glucose) that are used by heterotrophs
• Carbon reservoirs


  • Animal and plant biomass
  • Fossil fuel deposits
  • Soil organic matter
  • Solutes in oceans
  • The atmosphere
  • Marine sediments and sedimentary rocks
• Carbon in the lithosphere

  • Organic material: coal, oil, natural gas, etc. formed from the conversion of soft-bodied organisms to gas, petroleum, or coal
  • Carbon in soil from humus, an organic component of soil
• Formation of coal, oil & natural gas

  From plant & marine plankton that died a long time ago and accumulated on the bottom of oceans or lakes
• Formation of limestone


  From marine organisms that incorporate dissolved calcium into calcium carbonate shells that sink to the bottom and remain buried in sediments for millions of years
• Terrestrial carbon cycle


  Photosynthesis takes up CO2, cellular respiration releases CO2, volcanoes and burning of fossil fuels contribute CO2 to the atmosphere
• Carbon in oceans


  1. Enters through diffusion (creates carbonic acid - H2CO3)

  2. Some sea life use carbonate ions (CO32−) to produce shells and body parts (coral, clams, some algae, etc.)
• Nitrogen

  Component of amino acids, proteins, and nucleic acids (complex organic substances present in living cells, especially DNA or RNA)
• Biological nitrogen fixation & nitrogen-fixing bacteria

  Atmospheric nitrogen must be converted to NH4+ (ammonium ion) or NO3- (nitrate) for uptake by plants
• Decomposition (ammonification) & ammonifying bacteria

  Organic nitrogen is decomposed to NH4+ by ammonification
• Nitrification & nitrifying bacteria

  NH4+ is decomposed to NO3- by nitrification
• Denitrification & denitrifying bacteria

  Denitrification converts NO3- back to N2
• Atmospheric Fixation


  Lightning breaks N2 bonds, forming nitric acids and nitrates
• Industrial Fixation: Haber process


  Converts atmospheric N2 to ammonia
• Decomposers (detritivores)


  Play a key role in the general pattern of chemical cycling
• Abiotic factors


  Control the rate of decomposition, such as temperature, moisture, and nutrient availability
• Rapid decomposition results in relatively low levels of nutrients in the soil
• Cold and wet ecosystems store large amounts of undecomposed organic matter as decomposition rates are low
• Decomposition is slow in anaerobic mud
• The remains of all living things are decomposed by bacteria in the process of ammonification. Ammonification bacteria (e.g., Bacillus vulgaris) is correlated with dissolved oxygen.