Tidal Marshes of Barnegat Bay: Nutrient History and Ecosystem

Tidal Marshes of Barnegat Bay: Nutrient History and Ecosystem Services
D.J. Velinsky1, T. Quirk2, C. Sommerfield3, J. Cornwell4, and M. Owens4
1Patrick Center for Environmental Science
The Academy of Natural Sciences of Drexel University
2Department of Oceanography and Coastal Sciences, Louisiana State University
3School of Marine Science & Policy, University of Delaware
4Center for Environmental Science, University of Maryland‐Horn Point
May 2015
Barnegat Bay Comprehensive Research
NJ Department of Environmental Protection
Outline
•
•
•
•
•
•
•
Tidal wetlands of Barnegat Bay
Processes in tidal wetlands
Focus of both studies
Sediment history and burial
Denitrification in wetlands
Mass Balance
Summary
Barnegat Bay Watershed N load: 4.6 to 8.6 x 105 kg N yr‐1
(from 1998 to 2011; Baker et al. 2014) Symptoms of Eutrophication
• phytoplankton and macroalgae blooms
• brown tide and HABs
• alteration of benthic communities
• loss of seagrass and shellfish beds
Wetlands provide valuable
ecosystem services!
• Water quality improvement
(e.g. chemical transformation)
• Floodwater retention and protection
• Biodiversity islands and corridors
• Carbon, nitrogen, phosphorus
(i.e., chemical) sequestration
• Locations for human relaxation and
nature observation/education
Wetlands of Barnegat Bay
Areal Extent:
26,900 acres
Saline Wetlands: 21,800 acres
Tidal Freshwater: 5,100 acres
Data from V. Depaul (USGS)
Wetland accretion and erosion
Accretion
• Local accretion = mass accumulation ÷ soil bulk density
cm/y g/cm2/y g/cm3
• Absolute accretion = local accretion + subsidence
NJDEP Barnegat Bay Comprehensive Research
Objectives of Projects:
1. Evaluate permanent nitrogen (N) removal services provided by Barnegat Bay coastal wetlands:
• Sediment burial of nitrogen, carbon and phosphorus (Yr 0)
• Bay‐wide seasonal denitrification rates in salt marshes (Yr 1)
• Mosquito control (OMWM) ponds impact on denitrification (Yr 2)
•
How do OMWMs impact ecosystem services?
2. Combine data to obtain an overall estimate of N removal services provided by Barnegat Bay wetlands.
Q: What is the fate of nitrogen and other nutrients in the Bay?
Wetland Nitrogen Cycle
N2 (g) flux
Tidal Exchange
Plant uptake
Algae and Spartina
NO3‐ + NH4++ DON
NH4+
flux
NO3‐
flux
WATER
Watershed N&P Loadings
SEDIMENT
Organic N
OO
Burial
O 4+
NH
Net Ammonification
O 3‐
NO
Net Nitrification
NO2 (g)
Denitrification
Barnegat Bay
Spatial coverage of the bay
 North ‐ High nutrient input
‐ Lower salinity
 Mid‐bay Barrier Island
‐ Mid gradient of salinity/nutrients
 South ‐ Lower nutrient input
‐ Higher salinity Year 0 and 1 Sites
Year 2 Sites
Photos from the Field
Nitrogen Burial in Barnegat Bay Wetlands
BB1B
Nitrogen (%)
Cs-137 (dpm/g)
0
2
4
6
8
0
Depth (cm)
10
c. 1963
S Cs‐137 = 0.25 cm yr‐1
20
30
40
10
Wetland Nitrogen Cycle
N2 (g) flux
Tidal Exchange
Plant uptake
Algae and Spartina
NO3‐ + NH4++ DON
NH4+
flux
NO3‐
flux
WATER
Watershed N&P Loadings
SEDIMENT
Organic N
OO
Burial
O 4+
NH
Net Ammonification
O 3‐
NO
Net Nitrification
NO2 (g)
Denitrification
Sampling Locations
• Reedy Creek (BB-1)
• Mid Bay-Wire Pond (BB-2)
• Oyster Creek (BB-3)
- discharge canal
• West Creek (BB-4)
Analytical Parameters
– Organic Carbon, Total Nitrogen
and Total Phosphorus
– Diatom Species Composition
– Stable Isotopes of Carbon (13C)
and Nitrogen (15N)
– Grain size (< 63 m; clay+silt)
– Radioactive Isotopes: 210Pb and
137Cs
Comparison Between Delaware and Barnegat Bays:
Accretion Rates
Tidal fresh and salt marsh accretion rates in Delaware Estuary:
All Sites
Mean 0.72 ± 0.21 cm/yr, n=29
Barnegat Bay Sites:
Max
1.1 cm/yr
Min
0.39 cm/yr
All Sites
Mean 0.25 ± 0.06 cm/yr, n= 4
Salt Marshes
Max 0.29 cm/yr
Mean 0.65 ± 0.17 cm/yr, n=17
Min 0.16 cm/yr
Max
1.0 cm/yr
Min
0.39 cm/yr
Tidal Freshwater Marshes
Mean 0.85 ± 0.24 cm/yr, n=12
Max
1.1 cm/yr
Min
0.60 cm/yr
6
1.5
Changes in N with Time
BB-1
TN
1.0
4
2
0.5
• Increase N concentrations starting
around the 1940s
15N-TN
0
0.0
1.5
• The 15N-TN increases from 0-1 per
mill to ~ 4 per mill at the surface
0.5
1.0
1.5 0.0
0.5
1.0
1.5 0.0
0.5
1.0
1.5
0.0
0.5
1.0
Sediment Depth (cm)
0
20
1.5
2
0.5
0
0.0
1.5
6
BB-3
4
1.0
2
0.5
0
0.0
6
1.5
BB-4
40
4
Col 6 vs Col 11
Col 6 vs Col 9
1.0
Total Sediment N
15N-TN
4
1.0
2
60
0.5
0
80
BB-1
100
BB-2
BB-3
BB-4
0.0
1800
1850
1900
Year
1950
2000
Sediment 15N (‰)
TN-Sediments (%)
Total Sediment Nitrogen (%)
• Suggest more sewage-derived N was/is
being introduced to the bay (..has it
changed?)
0.0
6
BB-2
How much N and P are Buried in the
Marshes of Barnegat Bay?
Nitrogen Accumulation Rates (mg N/cm2-yr)
0.0 0.2 0.4 0.6 0.8 1.0
0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0
Accumulation of N&P over Time
2000
• Using [N or P], sediment mass, and
accretion rates to calculate
accumulation rates over time
Time (years)
1980
1960
1940
1920
1900
BB-1
BB-2
BB-3
BB-4
Phosphorus Accumulation Rates (mg P/cm2-yr)
0.00 0.02 0.04 0.06 0.08
0.00 0.02 0.04 0.06 0.08
0.00 0.02 0.04 0.06 0.08
0.00 0.05 0.10 0.15
2000
• No distinct north-south gradient in rates
(highest rate for P at BB-4)
1980
Time (years)
• Rates change with time, with a general
increase in most cores starting in the
~1950s/1960s
1960
1940
1920
BB-1
BB-2
BB-3
BB-4
• Can use rates at the surface and over
time to estimate sequestration of N and
P from wetland sediments
1900
Burial rate = 5.2 ± 0.7 g N m‐2 yr‐1 (n = 4)
Barnegat Bay Marshes: Denitrification
Seasonal denitrification rates
 3 salt marshes in north, mid‐, and south bay
 6 cores per marsh
 3 times per year (May, July, October)
 Analyze cores for N‐ fluxes, oxygen demand, sediment carbon and nitrogen  Determine average bay‐wide flux rates (g N m‐2 d‐1)
Wetland Nitrogen Cycle
N2 (g) flux
Tidal Exchange
Plant uptake
Algae and Spartina
NO3‐ + NH4++ DON
NH4+
flux
NO3‐
flux
WATER
Watershed N&P Loadings
SEDIMENT
Organic N
OO
Burial
O 4+
NH
Net Ammonification
O 3‐
NO
Net Nitrification
NO2 (g)
Denitrification
Factors that can Limit Denitrification in Sediments
• dissolved oxygen
• hydrogen sulfide
• lower pH
• liable carbon source (i.e., easily degradable OC)
• available nitrate (coupling of nitrification‐denitrification)
• Question: Importance of Anammox and DNRA pathways?
Denitrification Rates in Three Salt Marshes in Barnegat Bay
200
May
July
October
Reedy IBSP
Horse
N2 production rate (umol/m2/hr)
180
160
140
120
100
80
60
40
20
0
Reedy
IBSP
Horse
Site
Other salt marshes
12 – 290 μmol/m2/hr
(Valiela et al. 2000)
MONTH
May
July
October
N2 Production (μmol/m2/hr)
83 ± 14ab
121 ± 20a
49 ± 19b
What are Open Marsh Water Management
(OMWM) Systems?
Strafford 2002
Strafford 2013
Mosquito control: since the 1970’s the Ocean County Mosquito Extermination
Commission has created over 9,000 ponds across 12,000 acres of salt marsh in
Barnegat Bay, NJ.
• Limited amount of information about how it affects marsh accretion and
ecosystem services
• How much is enough?: balance between human health and ecosystem health
Variation in Vegetated Sediments: Limited Ability to Detect Differences
N2 production rate (umol/m2/hr)
250
July 17, 2012
Horse Creek (southern bay)
200
150
100
50
0
Veg Control
Veg OMWM
Treatment
Pond OMWM
Comparison of N2 Production Among Study Sites 200
Edwin B. Forsythe National Wildlife Refuge: 2014
May
Jul
Oct
150
100
50
Site characteristics
C
re
ek
N
on
D -O
itc M
he WM
s
O
D MW
itc M
he
s
0
Po
nd
s
N2 production (umol m-2 hr-1)
250
Summary of Denitrification Study
Open water (OMWM) vs Vegetated marsh
• Denitrification variable in vegetated marsh
• Much less variable in open water interior marsh sites • No substantial difference between marsh open water and vegetated sites
• No relationship between porewater sulfide and N2 production
Open Marsh Water Management (OMWM)
Wetland Nitrogen Cycle
N2 (g) flux
Tidal Exchange
Plant uptake
Algae and Spartina
NO3‐ + NH4++ DON
NH4+
flux
NO3‐
flux
WATER
Watershed N&P Loadings
SEDIMENT
Organic N
OO
Burial
O 4+
NH
Net Ammonification
O 3‐
NO
Net Nitrification
NO2 (g)
Denitrification
Comparison of Barnegat Bay Marsh Nitrogen Removal Rates Measured to Rates of Nitrogen Inputs to Barnegat Bay
5
Inputs (1989-2011; Median)
Marsh Burial:
Core Top Concentrations
Avg Concentrations (50yrs)
Burial as % of Inputs
Core Top Concentrations
Avg. Concentrations (50yrs)
Nitrogen (kg/yr X10 )
6.73
6.1 ± 0.02
5.2 ± 0.71
91%
77%
Marsh Denitrification:
May
July
Oct
Avg ± SD
Denitrification as % of Inputs
Total Removal
0.47
0.70
0.30
0.49 ± 0.20
7.30%
84-98%
Nitrogen inputs ranged from 4.6 to 8.6 X105 kg/yr (1989‐2011; Baker et al., 2014) Wetland area (26,900 acres, 1.1 X108 m2) are obtained from www.crssa.rutgers.edu/ projects/lc/ and V. Depaul (USGS)
Summary and Conclusions
• Remaining wetlands play important role in nutrient cycles in Bay
• Plant uptake‐sediment burial can sequester carbon, nitrogen and phosphorus (nutrient trading?)
• Denitrification is an important process for nitrogen removal in wetlands
• OMWM sites have similar rates in whole marsh
• Studies showcase the importance of BB wetlands and maintaining and increasing area
Acknowledgements
Patrick Center for Environmental Research
Roger Thomas
Paul Kiry
Mike Archer
Melissa Bross
Stephen Dench Megan Nyquist
Kirk Raper
Linda Zaoudeh
Paula Zelanko
We thank the support of Thomas Belton and NJ DEP.