water quality in stormwater detention ponds and the
TRANSCRIPT
Water quality in stormwater detention ponds and the impacts of pond discharges on ecosystem processes
within tidal creek receiving waters:
Erik M. Smith North Inlet - Winyah Bay National Estuarine Research Reserve University of South Carolina, Baruch Marine Field Laboratory
Funding provided by:
Collaborators: Amy Willman, Amber Stojak, Ashley Riggs, Tracy Buck,
Ben Lakish, Susan Denham, Angie Defore
Myrtle Beach
Charleston
Hilton Head
Created ponds have become a major feature of the coastal landscape
Pond delineation: 2006 Color IR DOQs; ground resolution of 1m Digitally delineated at a screen resolution of 1:3000
Total number = 14,446 Total area
= 8,659 hectares = 21,397 acres
= 86.6 km2
Geospatial inventory of ponds in coastal SC
Most stormwater ponds are detention ponds § Designed to capture “first flush” (typically 1st 0.5” of runoff) § Outlet structure discharges to adjacent surface water § Ultimately drain to coastal receiving waters.
How do water quality impacts in these (freshwater) ponds affect water quality conditions and ecosystem function in (marine) tidal receiving water?
Myrtle Beach
Surfside Beach
Pawleys Island
North Inlet
A.I.W. All Ponds
Study Ponds
Murrells Inlet
26 residential ponds 2 Undeveloped 7 Low density development 10 Medium density development 10 High density development
Pond size mean
Pond depth mean
All sampled ponds are freshwater.
: 0.25 – 13.6 acre = 4.3 acre
: 1.0 – 5.0 m = 2.0 m
Comparative study of 26 stormwater ponds spanning a range of development density
Comparative study of 26 stormwater ponds spanning a range of development density
Myrtle Beach
Surfside Beach
Pawleys Island
North Inlet
A.I.W. All Ponds
Study Ponds
Murrells Inlet
26 residential ponds 2 Undeveloped 7 Low density development 10 Medium density development 10 High density development
Sampling (8 times from June – September): • Nutrients (N & P in all forms, particulate & dissolved) • Organic carbon (particulate & dissolved, % labile) • Chlorophyll a • Diurnal O2 dynamics in surface & bottom waters à Net Ecosystem Production • Pond vertical structure and light attenuation
Mixing experiments: Effects of pond discharges on coastal marine waters
Total nutrient concentration variability across all ponds: To
tal N
itrog
en
(µg
L-1 )
No develop. Low Medium High max mean
min 10
100
1000
10000
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
Low: x = 466 Medium: x = 766 High: x = 1011
Tota
l Pho
spho
rus
(µg
L-1 )
1
10
100
1000
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
Low: x = 14 Medium: x = 62 High: x = 95
SCECAP “fair” and “poor” levels for coastal waters:
SCECAP “fair” and “poor” levels for coastal waters:
10
100
1000
10000
1.0 10.0 100.0 1000.0
Tota
l Nitr
ogen
(µg
L-1 )
Total Phosphorus (µg L-1)
Strong Relationship Between Total Nitrogen and Total Phosphorus
(all ponds, all sampling events)
“Redfield” Ratio 16N:1P (molar) ~7N:1P (mass)
Region of P deficiency
Region of N deficiency
y = 190x0.35 r2 = 0.60
p < 0.0001
Total phosphorus is a strong predictor of Chlorophyll across all ponds
0.1
1.0
10.0
100.0
1000.0
1.0 10.0 100.0 1000.0
Chl
orop
hyll
(µg
L-1 )
Total Phosphorus (µg L-1)
y = 0.4x1.02 r2 = 0.65
p < 0.0001
Nutrient Distributions: Particulate vs. Dissolved & Organic vs. Inorganic
0
20
40
60
80
100
Perc
ent
TN as Dissolved
TP as Dissolved
0
20
40
60
80
100
Ø TN dominated by DISSOLVED N.
Ø TP dominated by PARTICULATE P.
TN Dissolved as Inorganic
0
20
40
60
80
100
TP Dissolved as Inorganic
0
20
40
60
80
100
Ø TNdissolved dominated by DON.
Ø TPdissolved much more variable.
Nutrient Distributions: Particulate vs. Dissolved & Organic vs. Inorganic
0
20
40
60
80
100
0 40 80 120 160
% T
P D
isso
lved
as
Inor
gani
c
Total phosphorus (µg L-1)
LN(%DIP) = 1.5 – 0.6*LN(TP) r2 = 0.55; p < 0.0001
TP Dissolved as Inorganic
0
20
40
60
80
100
PON
POP
DON*
Recycling (excretion, grazing, etc.)
Uptake
Re- mineralization DOP
DIN DIP
Biomass
Dissolved Organics
Nutrient Input
(Substantially inorganic)
Box sizes indicate relative partitioning
of either N or P
Fate?
Conceptual Model of Nutrient Dynamics in Ponds
*DON as high C:N ratio DOM
§ Chlorophyll concentration § Phytoplankton primary production rate (14C method) § Bacterioplankton production rate (3H-Leucine method)
Quantify over 3 days of incubation under natural sunlight
Approach: Mix: 20 % filtered pond water with 80 % North Inlet water
Response Variables:
Filtered Pond Water
Coastal Water
20%
80%
3 day incubation in natural sunlight
Each day measure:
1. Chl (µg L-1) 2. PP (µg C L-1 h-1) 3. BP (µg C L-1 h-1)
What happens when this DON enters (N-limited) coastal marine waters?
Treatments (triplicate incubations): Ø 0.2 µm filtered pond water Ø D.I. water (control for dilution effects) Ø D.I. water with equivalent concentration of N as DIN (50:50 NH4:NO3)
What happens when this DON enters (N-limited) coastal marine waters?
Approach: Mix: 20 % filtered pond water with 80 % North Inlet water
Time (h) Time (h)
Chl
a (µ
g L-
1 )
0
5
10
15
20
25
30
35
0 20 40 60 80
Control
0 2 4 6 8 10 12 14 16 18 20
0 20 40 60 80
Control Pond Water Pond Water Inorganic N Inorganic N
Alg
al P
rodu
ctio
n (µ
g C
L-1
h-1
)
Max Phytoplankton Production Rate
Phytoplankton Biomass
Autotrophic response:
Bac
teria
l Pro
duct
ion
(µg
C L
-1 h
-1)
0
1
2
3
4
5
0 20 40 60 80
Control Pond Water Inorganic N
Time (h)
0
5
10
15
20
25
30
35
0 20 40 60 80
Control Pond Water Inorganic N
Alg
al P
rodu
ctio
n (µ
g C
L-1
h-1
)
Time (h)
Max Phytoplankton Production Rate
Bacterioplankton Production Rate
Autotrophic vs. heterotrophic responses:
Pond discharge effects relative to those from other sources
Hutchins PR, EM Smith, ET Koepfler, RF Viso, RN Peterson (2013) Metabolic responses of estuarine microbial communities to discharge of surface runoff and groundwater from contrasting landscapes. Estuaries and Coasts, in press.
Forest drainage Urban stormwater runoff
Pond discharge effects relative to those from other sources
0.0
0.5
1.0
1.5
2.0
2.5
24 72 24 72
Trea
tmen
t Res
pons
e C
ontr
ol
Phytoplankton Production
Bacterioplankton Production
Pond discharge
Forest runoff
Pond = Forest =
0.13 µM DIN 5.40 µM DIN
Pond = Forest =
668 µM DOC 1636 µM DOC
Time point Time point
0.0
5.0
10.0
15.0
20.0
25.0 Pond discharge
Forest runoff
Urban runoff
Trea
tmen
t Res
pons
e C
ontr
ol
Phytoplankton Production
Bacterioplankton Production
Pond = Forest = Urban =
0.13 µM DIN 5.40 µM DIN
203.22 µM DIN
Pond = Forest = Urban =
668 µM DOC 1636 µM DOC 2628 µM DOC
24 72 24 72 Time point Time point
Pond discharge effects relative to those from other sources
Summary Ø Stormwater detention ponds have become a major feature of the landscape
in coastal South Carolina. ~ 14,000 ponds within coastal zone, covering ~ 85 Km2 (~ 21,000 acres)
Ø Ponds exhibit a large range in nutrient and chlorophyll concentrations. § Development appears to increase TP more so than TN concentrations
• Relatively little variation in nitrogen within and across ponds • Substantial variation in phosphorus within and across ponds
Ø Chl concentrations more a function of TP variability, than TN variability
Ø Pond organic matter dominated by dissolved materials & ponds effectively convert DIN inputs to DON, which accumulates as high C:N DOM.
Ø Pond exports have little to no direct effect on marine autotrophic processes, but significantly stimulate heterotrophic processes. à Responses to pond discharges much smaller than response to direct
urban stormwater runoff