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Estuarine Cycles

Estuarine Cycles. Estuaries are the best cyclers in the world! . Sulfur. There are many forms of sulfur in estuaries Sulfur is a good oxidation-reduction element (redox) Seawater contains high amounts of SO 4

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Estuarine Cycles

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  1. Estuarine Cycles Estuaries are the best cyclers in the world!

  2. Sulfur

  3. There are many forms of sulfur in estuaries • Sulfur is a good oxidation-reduction element (redox) • Seawater contains high amounts of SO4 • When sulfate is reduced it by phytoplankton, it becomes dimethylsulfoniopropionate (DMSP) to volatile dimethyl sulfide (DMS)

  4. DMS • The molecule DMS CH3-S-CH3 • Approximately 50% of the global flux of S is derived from the marine environment. • Oxidation of DMS leads to production of SO4 in the atmosphere

  5. The Reduction of Sulfate • Some SO4 reducing bacteria (SRB) are closely related with the rhizophere of Spartinaalterniflora (control biogeochemical cycling in marsh sediments)

  6. SRB • Some of the plant families include: Desufovibrionaceae Desulfobacteriaceae Examples…. Desulfovibriodesulfuricans Desulfobacterium spp.

  7. Back to Sulfates? • A significant fraction of sulfides by SR are reoxidized to sulfates at the oxic-anoxic sediment interface • Dissolved Sulfides can diffuse into bottom sediments and can contribute to further O2 depletion in estuaries through oxidation.

  8. Oxidation Reduction Potential • Measures the amount of oxidizers, those wanting to take oxygen from the environment. Some include: Chlorides, Bromides, Ozone Because these oxidizers steal electrons, there is a higher ORP reading! Higher voltage!

  9. ORP • The less available oxidizers, the lower the potential and lower the ORP reading which means there are more chances for a reducing environment • In short the more negative – reducing conditions, the more positive – oxidizing • Ranges -1200 mV to +1200 mV

  10. Sulfides • They are not retained in sediments in estuaries • Are variable based on location, depth and temperatures • Can also vary if there is iron present

  11. Carbon

  12. Carbon • It is necessary for biological functions and is the key element on earth (over 1,000,000 compounds) • Oxidation states from +4 to -4 • Has both long-term and short-term cycles • We will focus on the “carbonate reservoir” (Holmen, 2000).

  13. Carbonate Reservoir

  14. Complex Carbon Cycles • Methane and carbon dioxide are the gases that get attention as they are “greenhouse gases”

  15. Methane Carbon dioxide

  16. Inorganic Carbon • The processing of inorganic forms of carbon in phytoplankton are important for short-term process. CO2 O2

  17. Inorganic to Organic Form C Now an organic form for zooplankton to use for energy

  18. The Cycle Continues… CO2 Through heterotrophic functions (respiration), it is now back to the inorganic form

  19. Iron was found to be one of the limiting components to “control” phytoplankton populations

  20. How about increasing the amount of autotrophic species through iron fertilization? There is a Southern Ocean Iron Enrichment Experiment

  21. Ratios of Carbon Carbon was found to be in ratios with N as follows… C/V Terrestrial Leaves 100 Trees 1000Marine PlantsZostera marina 17 – 70Spartinaalterniflora 24 – 45 Marine Macroalgae Browns 30 (mean) Greens 10 – 60 Reds 20Microalgae & Microbes Diatoms 6.5 Greens 6 Bacteria 5.7 Fungi 10

  22. Carbon emissions? • Marshes, inner waters and tidal flats are thought to be the largest producers of carbon dioxide in terms of ecosystems. • Reasons, types of biota in estuaries, thus produce carbon dioxide. • Estuaries are thought to be net heterotrophic.

  23. Guess what this is?

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