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Aers 2010
1. SEASONAL PATTERNS OF NITROGEN RETENTION IN A RESTORED TIDAL
FRESHWATER STREAM OF THE MID-ATLANTIC COASTAL PLAIN
Joe Wood and Paul Bukaveckas
Virginia Commonwealth University, Department of Biology
3. • Describe seasonal patterns
and annualized budgets for Project Goals
Nitrogen in a recently
restored tidal freshwater
stream.
• Estimate seasonal variation
in ecosystem metabolism
parameters (using diel
dissolved oxygen curves)
• Determine controlling
factors of nitrogen
retention.
4. 13000 m3
Dam Breach confining
discharge to a 5 meter
passageway
1500m3
5. Water Fluxes
50000 0.4
45000 Chesapeake Bay Water Stage James River
0.2
40000
35000
0
30000
25000 -0.2
20000
-0.4
15000
m
W
m
E
V
R
g
n
h
u
o
S
3
a
c
x
e
g
a
u
d
e
s
10000
)
(
f
l
)
(
r
t
l
i
-0.6
5000
0 -0.8
Seo Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug
60000
50000
R² = 0.78
40000
30000
20000
10000
m
E
u
o
g
n
h
3
v
e
a
c
x
)
(
l
0
0.0 0.5 1.0 1.5 2.0 2.5 3.0
River depth (m)
6. 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%
7. 3,500
2,500
1,500
RETENTION
500
-500
DIN
-1,500
RELEASE
N
D
u
d
C
e
T
a
g
y
x
F
/
c
I
l
i
-2,500
-3,500
3,500 Sep Oct Dec Jan Feb Mar Apr May Jun Jul Aug
2,500
1,500
500
-500
TON
-1,500
O
N
d
u
C
e
T
a
g
y
x
F
/
c
i
l
-2,500
-3,500
3,500 Sep Oct Dec Jan Feb Mar Apr May Jun Jul Aug
TN
2,500
1,500
500
-500
-1,500
= (DIN
+ TON)
N
d
u
C
e
T
a
g
y
x
F
/
c
i
l
-2,500
-3,500
Sep Oct Dec Jan Feb Mar Apr May Jun Jul Aug
8. Metabolism Results
20.00 0.6
Kimages Creek 0.5
15.00
0.4
[NOx]
10.00
* 0.3
0.2
5.00
0.1
m
O
N
R
e
a
g
v
x
/
L
s
r
J
)
(
I
0.00 0
M
O
-5.00
d
g
2
/
-10.00
R
-15.00
GPP
-20.00
AE
Jan Feb Mar Apr May Jun Jul Aug
9. Controlling factors of NOx Retention
3,000 3,000
2,500 Sep 2,500 Sep
2,000 2,000
1,500 1,500 R² = 0.6439
R² = 0.8006
1,000 1,000
500 500
0 0
R
d
g
o
n
e
R
)
(
t
d
g
o
n
/
i
e
)
(
t
/
i
-500 -500
-1,000 -1,000
0 10 20 30 0 10,000 20,000 30,000 40,000
Temp (C)
Exchange Volume (m3)
3,000
2,500 Sep "GPP" R² = 0.6857
2,000
"R" R² = 0.4414
1,500
1,000
500
R
d
g
o
n
0
e
)
(
t
/
i
R² = 0.709
-500
-1,000
0.00 0.20 0.40 0.60 0.00 2.00 4.00 6.00 8.00 10.00
Ambient NOx (mg/L)
GPP or R (g O2/M2/Day)
10. Hurricane Kyle
In < 1% of the year, 10%
of total annual exchange
volume and 7% of annual
Nox Inflow, half of which
was retained. (3.5% of
annual NOx retained)
1.4
Rice Pier
1.2
Ches B.B.
1
0.8
0.6
0.4
0.2
m
w
R
h
b
u
d
e
a
g
s
r
t
)
(
l
i
0
23-Sep-08 24-Sep-08 25-Sep-08 26-Sep-08 27-Sep-08 28-Sep-08 29-Sep-08
11. .03
.47*
Temperature
Exchange
-.39 Volume
(driven by
GPP
water stage
Variation)
-.42* R 0.62*
0.86**
Ambient
.80**
[NOx]
NOx Mass
-.84** Retention
Path
* p < .05
analysis ** p < .01
12. .03
.47*
Water
Temperature
-.39 Tidal
Exchange
GPP
Volume
-.42* R 0.62*
0.86**
Ambient
.80**
[NOx]
NO3
-.84** Retention
* p < .05
** p < .01
13. Conclusions
• DIN Retention exhibits strong
seasonal variation that includes net
release.
Seasonal .47*
Variation -.05
(Temperature)
-.39 Exchange
• Metabolism, Exchange Volume and
GPP Volume
-.42*
R
0.62*
0.86**
.80**
Ambient Nitrate Concentration
Ambient
Nutrient
Concentrations
-.84** NOx Mass
Retention
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
retention.
14. Thank you!
• Dr. Joanna Curran • Jim Deemy
• Dr. James Vonesh • Julie Frank
• Dr. Chris Gough • Alex Fredua-Agyemang
• Michael Brandt • Mac Lee
• Kristen Cannatelli • Nader Shehadeh
• Maureen Daughtery • Nathan Conway
• Anne Schlegel
My Talk today is about some work I’ve done on seasonal patterns of nitrogen retention in a restored tidal creek
Ecosystems exhibit seasonal variation in processes which regulate nutrient retention. Ambient Nutrient Concentrations influence nutrient retention because only available nutrients may be retained by an ecosystem. Respiration and Gross primary production influence retention by assimilating nutrients into biomass. Tidal Exchange volume is more specific to these wide shallow channels, increases in exchange volumes results in greater inundation of riparian floodplain or wetlands which have profound influences on biogeochemical processes. Clarifying the strength and patterns of these processes was a main objective of this study
Our project goals include
This is an areal view of Kimages Creek. This dam was build in the 1920s to form lake charles. The dam was breached from a storm 3 years ago, resulting in Lake Drawdown and re-establishment of tidal exchange. When I speak of the restoration of this system it has been and extremely passive process in the sense that nothing has been done. One challenge of performing mass balances on tidal creeks is gauging accurate discharge in such a wide shallow habitat Some tidal creek studies have had to construct expensive weirs to be able to gauge tidal exchange, In our case the breach in the dam solves this problem by confining all tidal exchange to a small channel; as a result we have been able to create accurate budgets of this system. Once a month for a year we went out and characterized watershed inputs right above the head of tide and Tidal exchange across a complete tidal cycle. 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
Tidal exchange in this system showed strong seasonal variability which is driven by river stage which in turn is driven by Chesapeake Bay water stage. This seasonal trend in Chesapeake Bay Water stage is due to a variety of physical properties including wind patterns and thermal expansion of water. This relationship between water stage and exchange volume is exponetial with increased depths resulting in Extremely large exchange volumes.
The Annual balance between retention and release of nitrogen results in a relatively balanced system; The system acts as a sink for inorganic nitrogen but acts as a source for organic and total nitrogen looking at the annualized budgets you might not expect that much activity is going on here, If we compare the results for our system with the results of Bowden’s estimates we see that they are relatively similar.
Dissolved Inorganic Nitrogen is retained throughout warmer months with heavy nutrient retention occuring in early fall and late spring. The end of summer show decreased retention. Winter months show net release of inorganic nitrogen
We used a method to estimated metabolism which uses diel dissolved oxygen patterns. 3 factors are assumed to cause variation in temperature corrected dissolved oxygen concentrations. Photosynthesis, Respiration, and atmospheric Exchange. Our estimates indicate that this system is consistently heterotrophic. Diel estimates of metabolism are presented here. Kimages Respiration estimates are less variable than primary production. Also when Anbient nitrate levels decline by mid summer production levels begin decreasing. During August Kimages oxygen levels became extremely depleted and caused large atmospheric exchange estimates and thus reduced precision of our estimates.
Exchange Volume, Temperature, Metabolism and Ambient Concentration all exhibited relatively strong relationships with mass retention of NOx in this system. We did observe one date which represented Retention estimates which were similar to all other estimates combined. So we went back and tried to figure out what was going on on this dates.
We figured out that On September 24 th Hurricane Kyle was moving through the Atlantic ocean. Because the hurricane was off the coast a ways, we didn’t experience heavy precipitations due to the storm, but it did cause a significant rise in water stage in the Chesapeake bay. Which in turn had heavy influence on James river water stage. Our sampling date fell durring the beginning of this upwelling. This Represented the higher water level for the entire year and thus the highest exchange volume with tidal Kimages Creek. This 3 day event represented … When considering that our annual estimates of nitrate retention are only 5%, These types of events could be critical to nutrient retention.
We have attempted to use path analysis to determine causal relationships of factors which regulate nutrient retention. The results of this analysis indicate that a large proportion of the variation in nutrient retention which is caused by metabolism and Ambient Nutrient levels can be explained by temperature, Exchange volume influences on nutrient retention seem to be independent of temperature and instead releated to water stage which in our system Is most heavily influence by seasonal trends in Chesapeake bay water stage.
We have attempted to use path analysis to determine causal relationships of factors which regulate nutrient retention. The results of this analysis indicate that a large proportion of the variation in nutrient retention which is caused by metabolism and Ambient Nutrient levels can be explained by temperature, Exchange volume influences on nutrient retention seem to be independent of temperature and instead releated to water stage which in our system Is most heavily influence by seasonal trends in Chesapeake bay water stage.
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.
