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The biogeochemical cycling of phosphorus in marine systems

The biogeochemical cycling of phosphorus in marine systems. Introduction Sources of P Sinks of P Residence times P cycling within the ocean P distribution P composition P bioavailabity P turnover time conclusions. Sources of P. Riverine Atmospheric Volcanic. P Sinks.

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The biogeochemical cycling of phosphorus in marine systems

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  1. The biogeochemical cycling of phosphorus in marine systems • Introduction • Sources of P • Sinks of P • Residence times • P cycling within the ocean • P distribution • P composition • P bioavailabity • P turnover time • conclusions

  2. Sources of P • Riverine • Atmospheric • Volcanic

  3. P Sinks • Organic matter burial • P sorption and iron coprecipitation • Phosphorite burial • Hydrothermal processes

  4. Residence times • The global marine inventory of dissolved P is close to 3.2*1015mol P.The residence time of P relative to the known P sources ranges from 20000 to 8000 years.But based on the P sinks the residence time has dropped from 80000 to 10000 years.

  5. P cycling within the ocean • Dissolved inorganic P • Total dissolved and dissolved organic P

  6. Dissolved inorganic P • In most studies the dissolved inorganic P is characterized using phosphomolybdate under acidic conditions. • A more appropriate term for the fraction measured with this technique is the Soluble reactive phosphorus.

  7. Total dissolved and dissolved organic P • TDP is generally quantified by using high temperature and pressure in the presence of a strong oxidizing reagent in this manner all of the P within the sample is converted to inorganic P.

  8. P Distributions • The average global concentration of SRP in the oceans is 2.3 micromole and is by far the largest reservoir of dissolved P.

  9. P composition • The composition of P within marine systems has been difficult to constrain.

  10. P bioavailability • In the inorganic form P is most bioavailable

  11. P turn overtime • They are studding nutrients turn over times in the ocean now a days.

  12. Conclusions • It is clear that elucidating the cycling of all nutrients in marine systems is extremely important if we are to understand current controls on primary production. • P sinks could be much larger then current estimates as more information concerning the distribution and magnitude of phosphoritic deposits is known.

  13. Conclusions • The intensity of upper ocean P cycling, in particular, can have a direct impact on the magnitude of particulate matter exported from the euphotic zone to underlying sediments. Hence long term changes in P cycling will effect the residence time of P over geological time scales.

  14. Future outlook • There is still a lot of work to be done.

  15. Articles used. • The biogeochemical cycling of phosphorus in marine systems by Claudia R. Benitez-nelson. • Marine nitrogen: Phosphorus stoichiometry and the global N:P cycle by John A.Downing. • The relative influences of nitrogen and phosphorus on oceanic primary production.

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