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Denitrification in Marine Sediments: An Unknown Environmental Feedback

Denitrification in Marine Sediments: An Unknown Environmental Feedback. Owen L. Coyle September 24, 2010. Overfertilizing with Nitrogen. 1 of Gus Speth’s 8 Global Environmental Problems Known Consequences Algae Blooms Eutrophication Unknown Consequences Effects on N-Cycle.

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Denitrification in Marine Sediments: An Unknown Environmental Feedback

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  1. Denitrification in Marine Sediments: An Unknown Environmental Feedback • Owen L. Coyle • September 24, 2010

  2. Overfertilizing with Nitrogen • 1 of Gus Speth’s 8 Global Environmental Problems • Known Consequences • Algae Blooms • Eutrophication • Unknown Consequences • Effects on N-Cycle Duce et al. 2008

  3. Internal Cycling Sedimentary Processes In & Out The N Cycle courtesy Bess Ward

  4. Organic N NH4+ NO2- NO3- N-Transformation in Sediment N2 nitrite oxidation denitrification anammox Complicated ammonium oxidation dnrn ammonification dnra new biomass

  5. Mesocosms filled with Chesapeake Bay sediment and water Project Outline • Question • Does supply of organic matter affect N cycling in marine sediments? • Experimental Setup • simulate environment with 4 mesocosms • add NH4+ and NO3- (i.e. fertilizer) to all mesocosms • add little OM to 2 tanks (A & C) and lots to 2 tanks (B & D) • daily measurements of DIN (NH4+, NO2-, and NO3-)

  6. Skills Needed • Sample Mesocosms w/o contamination • acid-wash containers • prepare samples for long term storage at -40℃ • Measure DIN species • prepare standards and reagents • analyze using a spectrophotometer • Lab Protocol • keep thorough notes! • clean glassware • safely use hazardous chemicals

  7. Key Points: • NH4+ ∼ constant, then falls rapidly • NO2- peak < NO3- peak • Sequential: NH4+ → NO2- → NO3- Practically Identical Results-Low OM

  8. Key Points: • NH4+ initial rise • NO2- peak > NO3- peak • Sequential: NH4+→NO2-→NO3- Practically Identical Results-High OM

  9. Summary • Observed N cycling was different in high and low treatments • Data will be used to model sedimentary N processes • I would like to revisit this topic in my JP

  10. Thank You To: • Andrew Babbin • Bess Ward • Sarah, Jenna, Johanna, and all of the office mates and lab mates who made me feel at home

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