denitrification in marine sediments: an unknown environmental feedback
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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. - PowerPoint PPT PresentationTRANSCRIPT
Denitrification in Marine Sediments: An Unknown Environmental Feedback
Owen L. CoyleSeptember 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
Duce et al. 2008
The N Cycle
N2
N2
Phytoplankton(marine food web)
Organic N
sinking, mixing
Organic NNO3N2
NO3
atmosphere
overlyingwater
sediments
transport,mixing
denitrification mineralization
N fixation
courtesy Bess Ward
Internal Cycling
In & Out
Sedimentary Processes
N-Transformation in Sediment
Organic N
NH4+
NO2-
NO3-
N2
ammonification
ammoniumoxidation
nitrite oxidation
denitrification anammox
dnrn
dnra
new biomass
Complicated
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-)
Mesocosms filled with Chesapeake Bay sediment and water
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!keep thorough notes!
- clean glassware
- safely use hazardous chemicals
Key Points:•NH4
+ ∼ constant, then falls rapidly•NO2
- peak < NO3- peak
•Sequential: NH4+ → NO2
- → NO3
-
Practically Identical
Results-Low OM
Results-High OM
Practically Identical
Key Points:•NH4
+ initial rise•NO2
- peak > NO3- peak
•Sequential: NH4+→NO2
-→NO3-
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
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