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Denitrification in Delaware Bay Tidal Marshes and Creeks

Denitrification in Delaware Bay Tidal Marshes and Creeks. February 2011 Mike Owens, Jeffrey Cornwell Chesapeake Biogeochemical Associates & UMCES Horn Point Laboratory Delaware Estuary Science and Environmental Summit. Sediment Fluxes.

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Denitrification in Delaware Bay Tidal Marshes and Creeks

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  1. Denitrification in Delaware Bay Tidal Marshes and Creeks February 2011 Mike Owens, Jeffrey Cornwell Chesapeake Biogeochemical Associates & UMCES Horn Point Laboratory Delaware Estuary Science and Environmental Summit

  2. Sediment Fluxes • July 19, 2007: Cores collected for subtidal fluxes at 4 stations (triplicate cores) • July 23, 2007, April 27, 2008: Cores collected for marsh fluxes (2 marsh cores, 1 creek core). Standard fluxes carried out both time, plus two levels of NO3- addition in 2007 • We utilized our “standard” core incubation procedures and measured fluxes of ammonium, nitrate, di-nitrogen, oxygen and soluble reactive phosphorus.

  3. Study Goals • Measure net nutrient fluxes at the sediment-water interface of Murderkill River, creek and marsh environments • Utilize N2:Ar approach to measure denitrification to examine denitrification in high and low nitrate seasons • Compare denitrification rate estimates to other nitrogen sinks (i.e. burial) and to estimates of N input

  4. Atmospheric DIN Wetland Plant Community DIN + PN Surface Water Nitrogen N2-N Point/Non-Point N Inputs 3 2 DIN DIN 4 Wetland Soil DIN + PN 1 • Measured Parameters • NOx flux into soil • NOx flux into soil • NH4+ efflux from soil • Soil denitrification • Nitrogen burial Groundwater DIN Exchange 5 “Permanent” Burial

  5. Putting Microbes to Work Denitrification requires 1) reducing conditions (no oxygen) and 2) a source of nitrate (NO3-) In many environments, nitrate come from the oxidation of ammonium (nitrification) This process represents a bona fide loss of nitrogen; burial, incorporation into fish and washout at the bay mouth are the other major sinks for nitrogen

  6. Marshes

  7. Nitrate Addition Experiment July 2007

  8. Conclusions • Marsh nitrogen burial and denitrification rates are similar. Both could account for an important portion of watershed N inputs. • Denitrification is similar in early spring to summer rates, despite different nitrate sources (summer nitrification, spring water column nitrate)

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