hypoxia in the surf zone of the grand strand: likely causes

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Hypoxia in the Surf Zone Hypoxia in the Surf Zone of the Grand Strand: of the Grand Strand: Likely Causes Likely Causes Azure Bevington, Susan Libes, Joseph Bennett, Amanda Hall, Neil Capper and Eric Tosso, Coastal Carolina University, Conway, SC

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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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Page 1: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 2: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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.

Page 3: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 4: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes
Page 5: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes
Page 6: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 7: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 8: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

0 m

3 m

?Low DO5 m

Longitudinal Model of Hypoxic Zone

Pier

+ 100 to 200 m

Page 9: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes
Page 10: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 11: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes
Page 12: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 13: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 14: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 15: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 16: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 17: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 18: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 19: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 20: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes
Page 21: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 22: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 23: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 24: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 25: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 26: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 27: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

Is this a one-time event?

Should we be worried?

Page 28: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

-

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

Page 29: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

Future Frequency of Hypoxia

• Frequency of Upwelling– Global Climate Change

• Stormwater Runoff– Global Climate Change– Increase in population & impervious cover

Page 30: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

Potential Impacts

• Hard Bottom Communities

• Fisheries– Overfishing

• Harmful Algal Blooms

Page 31: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

< 0.5 m sediment cover

Potential Hard Bottom Habitat

Page 32: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

3 m

Typical 4 s waves along Grand Strand constrain wind mixing to upper 3 m (Gayes, pers. comm.)

Hard Bottoms start

Page 33: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

Potential Impacts

• Hard Bottom Communities

• Fisheries– Overfishing

• Harmful Algal Blooms

Page 34: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 35: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes
Page 36: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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

Page 37: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes
Page 38: Hypoxia in the Surf Zone of the Grand Strand: Likely Causes

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)