Denitrification in Delaware Bay Tidal Marshes and Creeks
Denitrification in Delaware Bay y Tidal Marshes and Creeks February 2011 Mike Owens, Owens Jeffrey Cornwell Chesapeake Biogeochemical Associates & UMCES Horn Point Laboratory Delaware Estuary Science and Environmental Summit
Sediment Fluxes July 19, 2007 2007: C Cores collected J l 19 ll t d for subtidal fluxes at 4 stations (triplicate cores) J l 23 July 23, 2007 2007, A Aprilil 27 27, 2008 2008: Cores collected for marsh fluxes (2 marsh cores, 1 creek core). ) Standard St d d flfluxes carried i d out both time, plus two levels of NO3- addition in 2007 W utilized tili d our ““standard” t d d” core We incubation procedures and measured fluxes of ammonium, i nitrate, it t didi-nitrogen, it oxygen and soluble reactive phosphorus.
Study Goals Measure nett nutrient att the M t i t fluxes fl th sediment--water interface of Murderkill sediment River, creek and marsh environments Utilize N2:Ar approach pp to measure denitrification to examine denitrification in high and low nitrate seasons Compare denitrification rate estimates to other nitrogen sinks (i (i.e. e burial) and to estimates of N input
Subtidal
Marsh&Subtidal
MK 01 MK 02 MK 03 MK 04
MK 05 MK 05 MK 07 MK 08 MK 09 MK 10
210Pb-Dated
Geochron A Geochron B
MK 04 04, MK 09 09, Geochron A Plot Together
Atmospheric DIN
DIN + PN
Point/Non-Point N Inputs
Surface Water Nitrogen
2
Wetland Plant Community
DIN
DIN
3
DIN + PN
1 Measured Parameters 1. 2. 3. 4. 5.
NOx flux into soil NOx flux into soil NH4+ efflux from soil Soil denitrification Nitrogen burial
Wetland Soil
Groundwater DIN Exchange
5
“Permanent” Burial
N2-N
4
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
DON Flux
NH4+ Flux
NO3Flux
N2 Flux
PON D Deposition ii WATER SEDIMENT
NH4+
PON
DON Burial
NO3-
Net Net Ammonification Nitrification
N2
Denitrification
750
O2
0
N2-N
500
-2 2
Sedimentt-Water Excchange Ratte mol m h
-1
-500 -1000
250
-1500 -2000
0
-2500 -3000 2000
250 0
1500
+
-250
NH4
1000
-500 500
NO2+3-
-750
500
-1000 0
-1250
-500
-1500 Murderkill Main
Murderkill Creeks
St. Jones Broadkill
Murderkill Main
Murderkill Creeks
St. Jones Broadkill
Marshes 300
250
-2
N2-Nmoles m h
-1
-500 -2
O2moles m h
July April
Marsh
-1
0
-1000
200
150
100
50
-1500 0 10
-2000
9
8
7
6
5
Site
Marsh SOD
-2500 8
7
6
5
Site 200 -1
Marsh
-2
100
+
9
NH4 moles m h
10
0
-100 10
9
8
7
Site
6
5
-1 -2
S Sediment t-Water E Exchange e Rate m mol m h
1000
1000
500
+ NH4
500
0
0
-500
-500
-1000
-1000 Murderkill Marsh I
Murderkill Creek I&II Marsh II
-
NO2+3
Murderkill Marsh I
Murderkill Creek I&II Marsh II
400
-2
N2-N Fluxx moll m h
-1 1
350 300 250 200 150 100 50 0
Murderkill M hI Marsh
Murderkill M Marsh h II
Creek I&II
Nitrate Addition Experiment July 2007
N2--N Flux x (mo ol m-2h-1)
350
N=15
N=15
N=19
N=5
100-150
>150
300 250 200 150 100 50 0 0-50
50-100
Nitrate Range (mol L-1)
Loading High Loading Low Net DIN Denitrification + Burial Burial Denitrification
-60
-40
-20
0
20
40
60 -2
-1
Nitrogen Flux Rate g m y
80
Conclusions Marsh nitrogen burial and denitrification rates are similar. Both could account for an important portion of watershed N inputs. inputs Denitrification is similar in early spring to summer rates, despite different nitrate sources (summer nitrification nitrification, spring water column nitrate)
Sediment Fluxes July 19, 2007 2007: C Cores collected J l 19 ll t d for subtidal fluxes at 4 stations (triplicate cores) J l 23 July 23, 2007 2007, A Aprilil 27 27, 2008 2008: Cores collected for marsh fluxes (2 marsh cores, 1 creek core). ) Standard St d d flfluxes carried i d out both time, plus two levels of NO3- addition in 2007 W utilized tili d our ““standard” t d d” core We incubation procedures and measured fluxes of ammonium, i nitrate, it t didi-nitrogen, it oxygen and soluble reactive phosphorus.
Study Goals Measure nett nutrient att the M t i t fluxes fl th sediment--water interface of Murderkill sediment River, creek and marsh environments Utilize N2:Ar approach pp to measure denitrification to examine denitrification in high and low nitrate seasons Compare denitrification rate estimates to other nitrogen sinks (i (i.e. e burial) and to estimates of N input
Subtidal
Marsh&Subtidal
MK 01 MK 02 MK 03 MK 04
MK 05 MK 05 MK 07 MK 08 MK 09 MK 10
210Pb-Dated
Geochron A Geochron B
MK 04 04, MK 09 09, Geochron A Plot Together
Atmospheric DIN
DIN + PN
Point/Non-Point N Inputs
Surface Water Nitrogen
2
Wetland Plant Community
DIN
DIN
3
DIN + PN
1 Measured Parameters 1. 2. 3. 4. 5.
NOx flux into soil NOx flux into soil NH4+ efflux from soil Soil denitrification Nitrogen burial
Wetland Soil
Groundwater DIN Exchange
5
“Permanent” Burial
N2-N
4
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
DON Flux
NH4+ Flux
NO3Flux
N2 Flux
PON D Deposition ii WATER SEDIMENT
NH4+
PON
DON Burial
NO3-
Net Net Ammonification Nitrification
N2
Denitrification
750
O2
0
N2-N
500
-2 2
Sedimentt-Water Excchange Ratte mol m h
-1
-500 -1000
250
-1500 -2000
0
-2500 -3000 2000
250 0
1500
+
-250
NH4
1000
-500 500
NO2+3-
-750
500
-1000 0
-1250
-500
-1500 Murderkill Main
Murderkill Creeks
St. Jones Broadkill
Murderkill Main
Murderkill Creeks
St. Jones Broadkill
Marshes 300
250
-2
N2-Nmoles m h
-1
-500 -2
O2moles m h
July April
Marsh
-1
0
-1000
200
150
100
50
-1500 0 10
-2000
9
8
7
6
5
Site
Marsh SOD
-2500 8
7
6
5
Site 200 -1
Marsh
-2
100
+
9
NH4 moles m h
10
0
-100 10
9
8
7
Site
6
5
-1 -2
S Sediment t-Water E Exchange e Rate m mol m h
1000
1000
500
+ NH4
500
0
0
-500
-500
-1000
-1000 Murderkill Marsh I
Murderkill Creek I&II Marsh II
-
NO2+3
Murderkill Marsh I
Murderkill Creek I&II Marsh II
400
-2
N2-N Fluxx moll m h
-1 1
350 300 250 200 150 100 50 0
Murderkill M hI Marsh
Murderkill M Marsh h II
Creek I&II
Nitrate Addition Experiment July 2007
N2--N Flux x (mo ol m-2h-1)
350
N=15
N=15
N=19
N=5
100-150
>150
300 250 200 150 100 50 0 0-50
50-100
Nitrate Range (mol L-1)
Loading High Loading Low Net DIN Denitrification + Burial Burial Denitrification
-60
-40
-20
0
20
40
60 -2
-1
Nitrogen Flux Rate g m y
80
Conclusions Marsh nitrogen burial and denitrification rates are similar. Both could account for an important portion of watershed N inputs. inputs Denitrification is similar in early spring to summer rates, despite different nitrate sources (summer nitrification nitrification, spring water column nitrate)
