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Hypoxia in the Surf Zone of the Grand Strand: Likely Causes. Azure Bevington, Susan Libes, Joseph Bennett, Amanda Hall, Neil Capper and Eric Tosso, Coastal Carolina University, Conway, SC. Serendipity. Being in right place at the right time doing something else. - PowerPoint PPT Presentation
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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
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.
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
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
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
0 m
3 m
?Low DO5 m
Longitudinal Model of Hypoxic Zone
Pier
+ 100 to 200 m
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
Is this a one-time event?
Should we be worried?
-
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
Future Frequency of Hypoxia
• Frequency of Upwelling– Global Climate Change
• Stormwater Runoff– Global Climate Change– Increase in population & impervious cover
Potential Impacts
• Hard Bottom Communities
• Fisheries– Overfishing
• Harmful Algal Blooms
< 0.5 m sediment cover
Potential Hard Bottom Habitat
3 m
Typical 4 s waves along Grand Strand constrain wind mixing to upper 3 m (Gayes, pers. comm.)
Hard Bottoms start
Potential Impacts
• Hard Bottom Communities
• Fisheries– Overfishing
• Harmful Algal Blooms
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
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
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)