1. SEASONAL PATTERNS OF NUTRIENT RETENTION IN A RESTORED TIDAL
FRESHWATER STREAM OF THE MID-ATLANTIC COASTAL PLAIN
Joe Wood, Virginia Commonwealth University, Department of Biology
2. Outline
• Nutrient transport and associated problems
• Description of Tidal Freshwater Systems
• Site Description & Project Goals
• Methods
• Results
• Conclusions and implications
3. What are Nutrients?
•Elements whose
environmental
supply is low in
relation to
biological demand
(N, P)
•Small amounts of
nutrients can result
in large responses
from biotic
systems.
5. Watershed-scale budgets
Basic Terminology
•Sources vs. Sinks
•Inorganic (NH4,NO3) vs.
Organic forms
•Assimilation vs.
mineralization
•De-nitrification
6. Tidal Freshwater Systems
“Along the hydrologic continuum between streams and ocean
lies a unique ecotone where river meets estuary” Ensign et al
2008
•These systems are
ecologically distinct from
both non-tidal streams and
salt marshes but have
been understudied.
Gravity Tides
Fresh Water Salt
Headwaters Tidal Freshwater Oceans
7. Why are Tidal Freshwater Streams
“biogeochemical hotspots”?
1. Increased exposure to
active surfaces
(benthic layer)
2. Diverse chemical and
physical habitats
(anaerobic zones,
floodplains)
3. Higher Organic Matter
availability
(Neubauer et al 2009)
8. Ecosystem Metabolism
Photosynthesis:
CO2 + H2O + Light CxH2xOx + O2
Respiration: Gross Primary Production =
CxH2xOx + O2 CO2 + H2O total amount of energy (or
C) fixed via photosynthesis
per unit of time.
How do these
parameters influence Ecosystem Respiration=
Nutrient Retention? total amount of energy (or
C) used via respiration per
unit time.
9. .
Seasonal Variation
Primary
Production
Respiration
Exchange Volume
Ambient Nutrient
levels
Mass
Nutrient
Retention
10. Project Goals
• Characterize Annual nutrient Budgets for a recently restored
tidal freshwater stream.
• Estimate seasonal variation in Ecosystem Metabolism (using
diel dissolved oxygen patterns).
• Determine controlling factors of nutrient retention.
12. Until September 2006 When a
breach occurred in the dam in
Kimages Creek Was dammed
causing to formDrawdown, and
1927 Lake lake Charles
reconnecting tidal inputs to
Kimages creek.
This narrow breach provides the ability to
measure all exchange between Kimages
Creek and the James River.
13. Sampling Regime
Q = Discharge
(L/s)
X = Solute
Concentration
(mg/L)
QntXnt
Qtidal , Xtidal
Qout, Xout
X = Cl, NO3, NH4, TN, PO4, TP and DOC
Head of tide
14. Non-tidal input Stream Cl input
River Cl input
Chloride should
behave
conservatively, thus
producing un-altered
outflows.
A Conservative
Tracer (Chloride)
Tidal Exchange
15. Stream input
Non-tidal input
chemistry
River input
chemistry
Retained Nitrogen
A Non-Conservative
Tracer (Nutrients)
Tidal Exchange
18. Measuring Ecosystems Metabolism
16
DARK LIGHT
15
(R) (PS + R)
14
DO eq (mg/L)
13
12
11
10
9
8
0:00 9:30 19:00 4:30 14:00 23:30 9:00 18:30 4:00 13:30 23:00
Photosynthesis: CO2 + H2O + Light CxH2xOx + O2
Respiration: CxH2xOx + O2 CO2 + H2O
We Must also account for Atmospheric Exchange…
19. Atmospheric Exchange
Oxygen
To estimate Atmospheric Exchange (AE) we used
a method which assumes a constant boundary
layer thickness. Thus AE is only influenced by
Depth and Difference in Saturation.
20. Advective influences
12 0.08
DO
10
Depth
0.06
8
O2 (mg/L)
Depth (m)
6 0.04
4
0.02
2
0 0.00
During certain times of the year when oxygen
concentrations were drastically different
between sources, Kimages displayed advective
influences of Oxygen.
21. Results
• Water
• Nutrient
• Annualized Budgets
• Metabolism Estimates
• High Flow events
• Controlling factors of nutrient retention
22. Rhodamine Additions indicate this is a macro-tidal
system
Inflow Outflow Inflow
2.5
Rhodamine Flux (g/min)
I
2 n
j
1.5 e
c
1 t
i
0.5 o
n 96,80%
0
0 2 4 6 8 10 12 14 16 18
Time since rhodamine injection (hours)
23. Average Water Fluxes
8000
1500
3500
(Storage)
13000
All Units in M3/ Tidal Cycle
24. 40000
Water Fluxes 0.4
35000 Gloucester Point James River
0.2
Volume of Exchange (m3)
30000
0
Water Stage (m)
25000
20000 -0.2
15000
-0.4
10000
-0.6
5000
0 -0.8
In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out
Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug
Storage Tidal output Tidal Input Non-tidal input
60000
50000
Exchange volume (m3)
R² = 0.78
40000
30000
20000
10000
0
0.0 0.5 1.0 1.5 2.0 2.5 3.0
River depth (m)
25. Predicted Outflow - Actual outflow Predicted Outflow - Actual outflow
(NH3 mg/L)
NH4 (mg/L) NO3 (mg/L) (NOx mg/L)
(mg/L)
Cl Outflow (mg/L)
Measured Cl
-0.10
-0.05
-0.25
-0.20
-0.15
0.00
0.05
0.10
0.02
0.00
0.04
-0.06
-0.02
-0.12
-0.10
-0.08
-0.04
0
10
20
30
60
70
40
50
0
S
9/24/2008
10
O
10/24/2008
20
P = 0.0000
D
R² = 0.9909
12/9/2008
30
J
1/18/2009
40
F
2/21/2009
Predicted Cl (mg/L)
50
60
M
3/21/2009
Cl Inflow (mg/L)
1:1
70
A
4/25/2009
M
5/19/2009
J
6/19/2009
J
7/31/2009
A
8/19/2009
Predicted Outflow - Actual outflow Predicted Outflow - Actual outflow
TN (mg/L) (TN mg/L) TON (mg/L) (TON mg/L)
-0.150
-0.100
-0.050
-0.250
-0.200
0.000
0.050
0.100
-0.10
-0.05
-0.20
-0.15
0.00
0.05
0.10
S
9/24/2008
O
10/24/2008
D
12/9/2008
J
1/18/2009
F
2/21/2009
RELEASE
M
differences
3/21/2009
A
4/25/2009
M
5/19/2009
J
6/19/2009
J
RETENTION
7/31/2009
Nutrient Concentration
A
8/19/2009
26. Chloride Fluxes
1,600,000
1,400,000 Delta Storage
1,200,000 Total output
1,000,000 Tidal
g cl Flux/Tidal Cycle
800,000 Non-tidal
600,000
400,000
200,000
0
In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out
Sep Oct Dec Jan Feb Mar Apr May Jun July Aug
27. Inorganic Nitrogen Fluxes
7,000
"Change in Storage"
6,000
Total output
g NOx Flux/Tidal Cycle
5,000 "Change in Storage"
g NO3
4,000
Tidal
Total output
Tidal
3,000 Non-tidal
Non-tidal
2,000
1,000
0
2,500 In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out
Sep Oct Dec Jan Feb Mar Apr May Jun July Aug
2,000
In Out In Out In Out In Out In Out In Out In Out In Out In Out
g NH4 Flux/Tidal Cycle
g NH4
1,500
Dec Jan Feb Mar Apr May Jun July Aug
1,000
500
0
In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out
Sep Oct Dec Jan Feb Mar Apr May Jun July Aug
28. 30,000
25,000 "Change in Storage"
g DIN Flux/Tidal Cycle
20,000
Total output
g DIN 15,000
10,000
Tidal
Non-tidal
5,000
0
30,000 In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out
25,000 Sep Oct Dec Jan Feb Mar Apr May Jun July Aug
g TON Flux/Tidal Cycle
20,000
g TON
15,000
n Out In Out In Out In Out In Out In Out In Out In Out In Out
10,000
Dec Jan 5,000 Feb Mar Apr May Jun July Aug
0
30,000 In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out
Sep Oct Dec Jan Feb Mar Apr May Jun July Aug
25,000
g TN Flux/Tidal Cycle
20,000
g TN
15,000
10,000
5,000
0
In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out
Sep Oct Dec Jan Feb Mar Apr May Jun July Aug
29. 1,800
1,600
"Change in Storage"
1,400 Total "Change in Storage"
output
g PO4 Flux/Tidal Cycle
1,200
g PO4
Total output
1,000
Tidal Tidal
Non-tidal
800 Non-tidal
600
400
200
0
5,000 In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out
4,500 Sep Oct Dec Jan Feb Mar Apr May Jun Jul Aug
4,000
n Out In Out 3,500In Out In Out In Out In Out In Out In Out
g TP Flux/Tidal Cycle
3,000
g TP
Jan Feb 2,500 Mar Apr May Jun July Aug
2,000
1,500
1,000
500
0
300,000 In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out
250,000 Sep Oct Dec Jan Feb Mar Apr May Jun Jul Aug
g DOC
200,000
g DOC Flux/Tidal Cycle
150,000
100,000
50,000
0
In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out In Out
Sep Oct Dec Jan Feb Mar Apr May Jun July Aug
30. Tracer
1600
Experiments
∆ Storage
1400
g NH4 /Tidal Cycle
Injection
1200
1000
Output
800 Tidal
600 Non-tidal
400
200
0
2500 Inflow Outflow Inflow Outflow Inflow Outflow Inflow Outflow Inflow Outflow Inflow Outflow
g PO4 /Tidal Cycle
2000 Ambient Injection Ambient Injection Ambient Injection
May June August
1500
1000
500
0
Inflow Outflow Inflow Outflow Inflow Outflow Inflow Outflow Inflow Outflow Inflow Outflow
Ambient Injection Ambient Injection Ambient Injection
May June August
32. Annualized
Budgets
North River, MA
(Bowden et al
Kimages Creek, VA 1991)
in (kg) out (kg) diff (kg) % %
NH4 309 330 -21 -6.8% 1.2%
Nox 1046 994 52 5.0% 6.8%
DIN 1361 1323 38 2.8% 4.4%
DON 2605 2827 -222 -8.5%
TN 3966 4150 -184 -4.6%
Cl 65641 68451 -2809 -4.3%
DOC 32082 30820 631 4%
TSS 113494 125627 -6067 -10%
33. Metabolism 20 0.60
James RIver NOx (mg/L)
James River 0.50
15 [NOx]
0.40
Results 10
5
0.30
0.20
g O2/M2/d
0.10
0 0.00
-5
-10
-15
-20
Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug
20
Kimages Creek
15
10
5
g O2/M2/d
0
-5 R
-10 GPP
AE
-15
-20
Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug
34. Hurricane Kyle
In < 1% of the year, 10%
of total annual exchange
volume and 7% of
annual Nox Inflow, half
of which was retained.
1.4 4500
Residual water table height (m)
Cartersville Discharge (m3/s)
1.2 4000
3500
1
3000
0.8 2500
Rice Pier
0.6 2000
Ches B.B.
1500
0.4 Cartersvill Discharge 1000
0.2 500
0 0
23-Sep-08 25-Sep-08 27-Sep-08 29-Sep-08 1-Oct-08
39. Conclusions
• DIN Retention exhibits strong 3,500
2,500
g DIN Flux/Tidal Cycle
1,500
seasonal variation that includes net
500
-500
-1,500
-2,500
-3,500
release.
3,500 Sep Oct Dec Jan Feb Mar Apr May Jun Jul Aug
2,500
g TON Flux/Tidal Cycle
1,500
500
-500
-1,500
-2,500
-3,500 Seasonal .47*
3,500 Sep Variation Dec
Oct Jan Feb Mar Apr -.05
May Jun Jul Aug
2,500 (Temperature)
g TN Flux/Tidal Cycle
1,500
• Metabolism, Exchange Volume and
-.39 Exchange
500 GPP Volume
-.42*
-500 R
0.62*
-1,500
0.86**
-2,500 .80**
-3,500
Ambient
Ambient Nitrate Concentration Sep Oct
Nutrient Jan
Dec
Concentrations
-.84**
Feb
NOx Mass
Retention
Mar Apr May Jun Jul Aug
Path
regulate nitrate retention.
.62*
* p < .05
analysis ** p < .01
Hurricane Kyle
In < 1% of the year, 10%
• High flow events can significantly
of total annual exchange
volume and 7% of
annual Nox Inflow, half
of which was retained.
influence annual budgets of nutrient 1.4 4500
Residual water table height (m)
Cartersville Discharge (m3/s)
1.2 4000
3500
1
3000
0.8 2500
Rice Pier
retention.
0.6 2000
Ches B.B.
1500
0.4 Cartersvill Discharge 1000
0.2 500
0 0
23-Sep-08 25-Sep-08 27-Sep-08 29-Sep-08 1-Oct-08
40. Thank you!
• Dr. Paul Bukaveckas • Dr. Ed Crawford
• Dr. Joanna Curran • Jim Deemy
• Dr. James Vonesh • Alex Fredua-Agyemang
• Dr. Chris Gough • Mac Lee
• Michael Brandt • Nader Shehadeh
• Kristen Cannatelli • Nathan Conway
• Maureen Daughtery • Doug Perron
• Anne Schlegel • Brenda Nguyen
• Cat Luria • Charlie Wood
• Molly Sobotka • Drew Garey
• Brian Hasty • Elizabeth Snider
•
The Values of Tidal Freshwater Ecosystems:My talk is about Tidal Freshwater streams and their ability to remove Nitrogen which can cause problematic eutrophication in downstream ecosystems. These pictures are taken from the same place over the 4 seasons.
Before I get into the research behind our project I want to get everyone on the same page concerning why we think that nutrient dynamic are an important subject to study. All biological organisms are composed of a few elements.
Agriculture, Wastewater Treatment and increases in Impervious surfaces have all resulted in increased transport of N & P throughout watersheds. The immediate responses of increases in limiting agents results in large messy algal blankets. These are initially somewhat problematic for obvious reasons but secondary issues are even more problematic. Once these unsustainable blooms die and sink to the bottom of these estuaries they are decomposed by bacteria; These rotting algal mats deplete oxygen levels and result in suffocation of financially important organisms. Significant efforts in agriculture, development and water treatment are being made to reduce nutrient loads from making there way to sensitive coastal systems. It is important to understand nutrient transport to address this problem at the landscape scale
This slide needs to focus on
This slide needs to focus on
Before I Describe a few of the retention mechanisms, These systems exist above the saline gradients but below the point where tidal forces become stronger than gravitational forces. Generally the field of biogeochemistry is young but significant amounts of work has been performed in both the Head Waters as well as in coastal estuaries while these tidal freshwater have been less frequently described.
1. This is important because in stream ecosystems most activity occcurs within the benthos Tidal flood plains experience tremendous variation every tide. This type of variation can result in high rates of de-nitrification. These systems have tremendous amounts of organic matter which has the potential for transformations.
Here you should describe GPP and R.
In order to construct a budget for a given tidal cycle it is necessary to quantify all inputs and outputs. For Kimages Creek this includes Non-tidal inputs from the local kimages watershed, and tidal inputs from the James River. For a conservative constituent such as chloride we should be able to predict outflow based on our both of our inputs. With a non-conservative constituent that is in demand such as Nitrogen or phosphorous, the difference between our predicted
A common method of nutrient retention is to add a nutrient tracer In order to make comparisons between ambient levels of nutrient retention and
SHOW LIGHT DARK
Just to establish that we were monitoring outflow of inflow water, We performed to rhodamine additions to determine how long tidal inputs remain within the wetland system. Results indicate that 95% of all inputs return to the river. Subsequent tidal sampling indicates that approximately 5% of these inputs return to the system on the next rising tide.
This is an areal view of our study site. This dam was build in the 1920s but in the past few years was breached resulting in Lake Drawdown. The blue outlined areas represent the tidal stream channel while darker gray areas which often become inundated. This has been an extremely passive “restoration”. This Breach confines all tidal inputs and as a result we have been able to create accurate budgets of this system. Click:These arrows represent average discharge for our study period. You can see the hydrology of this system is dominated by tidal exchange with the James River, You can also see that inputs and outputs are asymmetrical over a tidal cycle, indicating change in storage . Also just note these green dots represent the sampling locations of our water quality sondes which record parameters such as depth, and DO.
“Here are the results from our water budget. For each given tide there are non-tidal and tidal inputs, Outputs, and the we assume the difference to be considered as a change in storage volume. If you take september as an example, about 10000 liters came in while 35,000 Liters left resulting in a 25,000 liter drainage from kimages on that day. If you look at may however 25000 m3 came in and only 15000 left resulting in an increase in the amount of water volume stored in Kimages Creek. I will refer back to these exchange volumes when we come to the nutrient budgets. Another thing to Note about this figure is the variability of tidal exchange. There is a strong seasonal pattern which results in reduced exchanges in winter with respect to spring and fall. There is also variability in the non-tidal inputs from the kimages watershed; which are generally much smaller than tidal exchange. James River water level predicts for the amount of exchange volume as is indicated in the Regression between. The question then becomes what predicts for James River water level and based on where our site is in the James River there are 2 obvious possibilities, James River discharge coming from runoff throughout the state of Virginia and sea level. It turns out a seasonal pattern in Chesepeake bay sea level is congruent with James River depth data at our site in comparrison with Discharge data from a site upstream. I have left this off to try to maintain simplicity.Here are the results for our hydrologic budget, I am going to go into a little bit of detail about this figure because several of the other results are in this same format.Total Inputs and outputs are consistently assymetrical, indicating in changes in storage. We inferred the change in storage to be the difference between total inflow and outflow. Notice the seasonal variability in volume of exchange and how it tracks James river depth, and also Chesapeake Bay Water stages.
The simplest way to illustrate the difference between source/sink functioning of the wetland is to look at inflow and outflow concentrations. When I am referring to inflow concentrations I mean non-tidal and tidal inputs (rephrase). The first plot is Chloride You can see that Inorganic forms of nitrogen (NH3 and NOx) exhibit similar patterns by retaining nitrogen durring spring and fall and releasing them durring winter. Organic Nitrogen and TN exhibit a different pattern and release N throughout the year. These only represent concentrations not Fluxes.In order to elaborate on the seasonal patterns of retention I have concentration difference between inflow and outflow plotted by month. The tidal stream acts to enrich waters in inorganic nitrogen during winter months and remove it during spring and summer. Organic Nitrogen which is inferred from total nitrogen results, shows a contrasting pattern with release retention during cool months and release during the growth season. Concentration differences are the most straightfoward way of looking at what is going on, but they don’t indicate fluxes because they don’t incorporate exchange volumes.
In order to discuss the flux of constituents we must incorporate the amount of water which is exchanged with concentrations. Because inflow and outflow volumes are asymmetrical it wouldn’t be appropriate to just compare the total mass which comes in or leaves on a given cycle, because changes in storage volume would dominate. Our approach was to look at total actual inflows and outflows and correct for changes in storage volume. This figure represents the movement of chloride. Here there is balance (within 10%) on each sampling date between inflow and outflow)
Here are the flux estimates for Dissolved inorganic Nitrogen. Largest retention events occurred during September and May. You can see that the releases which occurred durring winter actually represent small fluxes despite the large concentration differences that were observed.
Here DIN, TON and TN are plotted. You can see that TON estimates are much larger than DIN for most of the year, with the exception of the winter. Also you can notice that TN overall generally doe not show large differences between inflow and outflow.
Here DIN, TON and TN are plotted. You can see that TON estimates are much larger than DIN for most of the year, with the exception of the winter. Also you can notice that TN overall generally doe not show large differences between inflow and outflow.
In order to increase the variability in Ambient Nutrient concentrations we performed a series of injections; results did not indicate that injection or ambient measurements resulted in greater estimates. MUST ADD KEYADD % Retained for Ambvs inj.
In order to go from 12 daily budgets to an annualized budget for nutrient retention we needed to estimate exchange volumes between sampling dates. In order to do this we used the previously mentioned Depth-Exchange Volume Relationship.
The balance between retention and release of nitrogen results in a relatively balanced system; TP and SRP show heavier release, however we are more uncertain about these number because they did not exhibit as clear of seasonal patterns and thus our interpolations between dates are likely less accurate. If we compare the results for our system with the results of Bowden’s estimates we see that they are relatively similar. REMOVE TSS
Diel estimates of metabolism are presented here. Notice that the James river exhibits a much stronger seasonal pattern, and that respiration rates here are highly correlated with production while, Lake charles Respiration estimate are not correlated with production. During July and August oxygen levels became extremely depleted O2 levels at Kimmages Creek, such that we believe tidal exchange with the James river advectively enriched oxygen levels. Because this methods assumes that changes in Oxygen concentrations are due to P, R or Reaeration, we believe these values are skewed.
On September 24th our very first sampling data, Hurricane Kyle was moving through the Atlantic ocean. The storm brought a few showers across our study site, but did not make landfall until reaching Canada. Even though this event didn’t cause significant precipitation, it did cause a spike in Chesepeake bay water levels and thus James River Estuary water stage. The result was significant increases in exchange volume. This event was extremely important to our annualized budget and represented large percentages of fluxes in small time periods, similar to high flow events in non-tidal streams.
Need to point out that for path analysis you can only use dates which all data is present for.
We have attempted to use path analysis determine causal relationships of nutrient retention with limited success. This method normalizes correlation coefficients with respect to other correlations. All the controlling factors of Nitrate retention still appear important in this model however, the it appears that the path from temperature through production and ambient concentration are apparent while the path from temperature through EV and Respiration are independent.