hypoxia in the surf zone of the grand strand: likely causes azure bevington, susan libes, joseph...
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Hypoxia in the Surf Zone of the Hypoxia in the Surf Zone of the Grand Strand: Likely CausesGrand Strand: Likely Causes
Azure Bevington, Susan Libes, Joseph Bennett, Amanda Hall, Neil Capper and Eric Tosso, Coastal Carolina University, Conway, SC
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Serendipity
• Being in right place at the right time doing something else.
• Assessing the impact of new discharge pipe at 25th Ave S on eutrophication status of nearshore.
• Hypothesis: Stormwater runoff through discharge pipes contributes to nutrient loading in the nearshore.
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Horry County Beach Closingsn = 10 sites
116 125
215
593
0
100
200
300
400
500
600
700
2000 2001 2002 2003
Nu
mb
er
of
Be
ac
h C
los
ing
s
NRDC (2004) Testing the Waters 2004: A Guide to Water Quality at Vacation Beaches
Violation of Enterococcus Swimming Criteria
Violations of Federal Swimming Criteria for Enterococcus Along Grand Strand Beaches
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0
1
2
3
4
5
6
24 26 28
De
pth
(m
)
0
1
2
3
4
5
6
34.5 35.0 35.5 36.0
0
1
2
3
4
5
6
0 1 2 3 4 5 6
De
pth
(m
)
0
1
2
3
4
5
6
0 20 40 60 80 100
DO (ppm) % Saturation
Temperature (oC) Salinity
2nd Ave N. Pier 7/20/2004
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Bottom Water Quality: Longitudinal Transect Along Pier
24.5
25.0
25.5
26.0
26.5
27.0
27.5
28.0
0 2 4 6Bottom Depth (m)
Te
mp
era
ture
(o
C)
0
1
2
3
4
5
6
0 2 4 6Bottom Depth (m)
DO
(p
pm
)
34.6
34.8
35.0
35.2
35.4
35.6
35.8
36.0
0 2 4 6Bottom Depth (m)
Sa
linit
y
0
20
40
60
80
100
0 2 4 6Bottom Depth (m)
% S
atu
rati
on
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0 m
3 m
?Low DO5 m
Longitudinal Model of Hypoxic Zone
Pier
+ 100 to 200 m
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Time-line
• Surface Cooling: July 1 – July 30• Rain fall
– 7/9, 1.0 inches– 7/18, 2.2 inches
• Sampling – 7/20: 2nd Ave N and Springmaid– 7/22: 2nd Ave N and Springmaid – 7/23: Cherry Grove and Apache + DNR transects
• Flounder Jubilee– July 15 – 23– July 23 – 28: tapered down
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0.0
0.5
1.0
1.5
2.0
2.5
6/1
6/5
6/9
6/1
3
6/1
7
6/2
1
6/2
5
6/2
9
7/3
7/7
7/1
1
7/1
5
7/1
9
7/2
3
7/2
7
7/3
1R
ain
(in
)
Withers Swash Midway Swash
Flounder runs start
Cold Event
Hypoxia first observed
Rain Fall Amounts Near Locations of Major Freshwater Input to Surf Zone
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Time-line
• Surface Cooling: July 1 – July 30• Rain fall
– 7/9, 1.0 inches– 7/18, 2.2 inches
• Sampling – 7/20: 2nd Ave N and Springmaid– 7/22: 2nd Ave N and Springmaid – 7/23: Cherry Grove and Apache + DNR transects
• Flounder Jubilee– July 15 – 23– July 23 – 28: tapered down
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DO Concentration in Bottom Water During Hypoxic Event
0
1
2
3
4
5
6
GardenCity
Surfside MyrtleBeach
State Park
SpringmaidPier
2nd Ave N.MB
ApachePier
CherryGrove Pier
DO
(p
pm
)
7/20/047/22/047/23/04
NOAA Estuarine Eutrophication Criteria Biological Stress >2 ppm, < 5 ppmHypoxic >0 ppm, < 2 ppmAnoxic 0 ppm
Off Shore
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8.01
8.07 8.06
8.20
8.09
7.83
8.02
7.6
7.7
7.8
7.9
8.0
8.1
8.2
8.3
Garden City Garden City Surfsidenearshore
Surfsideoffshore
Myrtle BeachState Park
Pier
2nd Ave Pier Apache Pier,nearshore
Mea
n p
HpH measurements along Grand Strand, July 23, 2004
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Surf Zone and Near Shore Dissolved Oxygen Percent Saturation
20
30
40
50
60
70
80
90
100
110
2/26 3/12 3/27 4/11 4/26 5/12 5/27 6/11 6/26 7/11 7/27 8/11
Sampling Date
Per
cen
t S
atu
rati
on
of
DO
2nd Ave N Springmaid Pier Surf Zone (25th Ave N)
Cherry Grove Pier Apache Pier
Cold Event
Bottomwater
Rain No Rain
Rain
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Time-line
• Surface Cooling: July 1 – July 30• Rain fall
– 7/9, 1.0 inches– 7/18, 2.2 inches
• Sampling – 7/20: 2nd Ave N and Springmaid– 7/22: 2nd Ave N and Springmaid – 7/23: Cherry Grove and Apache + DNR transects
• Biotic Impacts– Flounder Jubilee – Benthic invertebrate kills at Huntington Beach and Pawleys
Island
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Causative Agents
• Coastal Upwelling– Summer Cooling– Plankton Bloom
• Elevated Chlorophylls • Nutrients
• Stormwater Runoff– Pipes and swashes discharge on beach– Off-shore discharge pipes
• Raw Sewage Spill
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Surf Zone and Near Shore Chlorophyll a Levels
0
10
20
30
40
50
60
70
80
2/26 3/12 3/27 4/11 4/26 5/12 5/27 6/11 6/26 7/11 7/27 8/11
Sampling Date
Ch
l a (
pp
b)
2nd Ave N Springmaid Pier Surf Zone (25th Ave N)
Cherry Grove Pier Apache Pier
NOAA Estuarine Eutrophication Criteria Surface ConcentrationHypereutrophic >60 ppbHigh >20 ppb, < 60 ppbMedium >5 ppb, < 20 ppbLow >0 ppb, <5 ppb
Bottomwater
Cold Event
Rain No Rain Rain
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Total Nitrogen Concentration in the Surf Zone and Near Shore
0.000
0.050
0.100
0.150
0.200
0.250
0.300
0.350
0.400
0.450
4/23 5/3 5/13 5/23 6/2 6/12 6/22 7/2 7/12 7/22 8/1Sampling Date
Co
nce
ntr
atio
n (
pp
m N
)
2nd Ave N Springmaid Pier Surf Zone (25th Ave N)
Cherry Grove Pier Apache Pier
NOAA Estuarine Eutrophication Criteria Maximum Dissolved Surface ConcentrationHigh >1ppmMedium >0.1 ppm, < 1 ppmLow >0 ppm, <0.1 ppm
Bottomwater
Cold Event
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Total Phosphorus Concentration in the Surf Zone and Near Shore
0.000
0.010
0.020
0.030
0.040
0.050
0.060
0.070
4/23 5/3 5/13 5/23 6/2 6/12 6/22 7/2 7/12 7/22 8/1Sampling Date
Co
nce
ntr
atio
n (
pp
m P
)
2nd Ave N Springmaid Pier Surf Zone (25th Ave N)
Cherry Grove Pier Apache Pier
NOAA Estuarine Eutrophication Criteria Maximum Dissolved Surface ConcentrationHigh >0.1ppmMedium >0.01 ppm, < 0.1 ppmLow >0 ppm, <0.01 ppm
Bottom water
Cold Event
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Nitrogen to Phosphorus Ratio in the Surf Zone and Near Shore
0.0
20.0
40.0
60.0
80.0
100.0
120.0
4/23 5/3 5/13 5/23 6/2 6/12 6/22 7/2 7/12 7/22 8/1
Sampling Date
N/P
2nd Ave N Springmaid Pier Surf Zone (25th Ave N)
Cherry Grove Pier Apache Pier
Bottom water
Cold Event
N deficient growth
P deficient growth
Guildford and Hecky, 2000
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Causative Agents
• Coastal Upwelling– Summer cooling– Plankton Bloom
• Elevated Chlorophylls • Nutrients
• Stormwater Runoff– Pipes and swashes discharge on beach– Off-shore discharge pipes
• Raw Sewage Spill
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Stormwater Runoff
• Tidal Creeks (swashes)– Withers Swash: 35 to 40 cfs non-rain, 12 MGD – Midway Swash: 10 to 15 cfs non-rain, 4 MGD
• Pipes on Beach Face– Diameter ( 2 to 3’)– 100+
• Outfall Pipes (n = 3)– 25th Ave S
• Two individual pipes• 1222’• 60” diameter• Installed June 2003• 32.35 cfs during 50-yr non-hurricane storm (8.6” in 24 hr)• Catchment area is 189 acres
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Causative Agents• Coastal Upwelling
– Summer cooling– Plankton Bloom
• Elevated Chlorophylls • Nutrients
• Stormwater Runoff– Pipes and swashes discharge on beach– Off-shore discharge pipes
• Raw Sewage Spill in NMB– July 13: few hundred gallons– July 21: 5000 gallons
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Is this a one-time event?
Should we be worried?
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-
200,000
400,000
600,000
800,000
1,000,000
1,200,000
Po
pu
lati
on
Es
tim
ate
1990 1995 2000 2005 2010 2020 2030
Year
Horry County Population Growth Projections
Permanent Overnight Day
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Future Frequency of Hypoxia
• Frequency of Upwelling– Global Climate Change
• Stormwater Runoff– Global Climate Change– Increase in population & impervious cover
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Potential Impacts
• Hard Bottom Communities
• Fisheries– Overfishing
• Harmful Algal Blooms
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< 0.5 m sediment cover
Potential Hard Bottom Habitat
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3 m
Typical 4 s waves along Grand Strand constrain wind mixing to upper 3 m (Gayes, pers. comm.)
Hard Bottoms start
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Potential Impacts
• Hard Bottom Communities
• Fisheries– Overfishing
• Harmful Algal Blooms
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Needs
• Monitoring
• Define normal for Nearshore Waters– Now using estuarine criteria– How much of these events are natural
• Translate this into management guidelines– Reduction of nonpoint loads
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Acknowledgments
• Bob Van Dolah, Mel Bell, George Reikerk, Dean Cain, SC DNR
• Denise Sanger, SC DHEC OCRM• Alan Lewitus, South Carolina Algal Ecology
Laboratory • Bob Pender, Ryan Day, Burroughs and Chapin
Center for Marine and Wetland Studies
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Surf Zone and Swashes, Myrtle Beach, SC
0
50
100
150
200
250
300
3/27 4/11 4/26 5/12 5/27 6/11 6/26 7/11 7/27
Sampling Date
Mo
lar
N t
o P
Drainage Basin 2 (ditch) Drainage Basin 1 (pool)