Nutrient cycles (carbon and phosphorous)

  • Nutrient cycle involves storage and transfer of nutrients through various components (living & Non living) of the ecosystem so that the nutrients are repeatedly used.
  • Three types.
    (1) Gaseous:- eg: Carbon (absorbed as CO2, Nitrogen, Oxygen (as vapours) reservoir pool is atmosphere / water.
    (2) Sedimentary :- eg: P, Ca, Mg. reservoir pool is lithosphere.
    (3) Mixed :- eg: sulphur, because both gaseous & non gaseous stores.
  • Carbon is the main component of all the organic compounds of protoplasm like carbohydrates, lipids, nucleic acids, enzymes and hormones, etc, thus may be considered basis of life.
  • The concentration of CO2 is 0.03% in atmosphere which is utilized by producers in photosynthesis for making food. According to an estimate A×1013 kg of carbon is fixed in the biosphere through photosynthesis annually.
  • Carbon constitutes 49% of dry weight of organisms.
  • Carbon in the atmosphere is present as CO2, in hydrosphere as dissolved CO2 or Carbornic acid or bicarbonates and in lithosphere as fossil fuels or carbonates and graphite in rocks.
  • During photosynthesis the carbon component of the atmosphere and hydrosphere decreases.
  • Carbon can be replenished by various method like:
    (i) Respiration
    (ii) Decomposition of organic wastes
    (iii) Burning of wood and fossil fuel
    (iv) Weathering of carbonate containing rocks
    (v) Volcanic eruption and hot springs.
  • Some carbon is being removed from circulation and added to lithosphere by hard carbonaceous shells, animal skeletons, fossilization, seepage of carbon rich water into interior earth and caring in forests during earthquakes.
  • Human activities have significantly influenced the carbon cycle. Rapid deforestation and massive burning of fossil fuel for energy and transport have significantly increased the rate of release of Co2 into the atmosphere.
  • Phosphorus is an inorganic component of biological membranes, nucleic acids and cellular energy transfer systems, phospholipids, bones and teeth.
  • Rock is the natural reservoir of phosphorous available in the form of phosphates.
  • The producers absorbs soluble phosphate from soft which is transferred to consumers through herbivores and then to decomposer available organic phosphate by death and decay of producers & consumers.
  • The phosphorus in lakes appears in inorganic, particulate organic and dissolved organic form.
  • In soil, there are mainly supplied as phosphorus inorganic and insoluble organic. The dissolved phosphate are very less.
  • The inorganic phosphate is lost in erosion & the soluble by leaching. The phosphorus in ocean basin is lost by sedimentation. The ocean phosphate is recovered by geological process when these sediment as exposed to newly elevated surface.
  • Mining process also recovers phosphates. As a result of weathering of these exposed rocks, inorganic phosphorus is added to soil.
  • Inside the soil, some phosphorus is lost through leaching. Similarity, a sufficient amount of phosphorus combines with calcium, iron or aluminum and becomes insoluble.

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