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. Assessing the impact of new discharge pipe at 25 th Ave S on eutrophication status of nearshore. Hypothesis: Stormwater runoff through discharge pipes contributes to nutrient loading in the nearshore.

Violations of Federal Swimming Criteria for Enterococcus Along Grand Strand Beaches

Salinity Temperature ( o C) % SaturationDO (ppm) Springmaid Pier 7/20/04

DO (ppm)% Saturation Temperature ( o C)Salinity 2 nd Ave N. Pier 7/20/2004

Bottom Water Quality: Longitudinal Transect Along Pier

0 m 3 m ? Low DO 5 m Longitudinal Model of Hypoxic Zone Pier 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: 2 nd Ave N and Springmaid –7/22: 2 nd Ave N and Springmaid –7/23: Cherry Grove and Apache + DNR transects Flounder Jubilee –July 15 – 23 –July 23 – 28: tapered down

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: 2 nd Ave N and Springmaid –7/22: 2 nd Ave N and Springmaid –7/23: Cherry Grove and Apache + DNR transects Flounder Jubilee –July 15 – 23 –July 23 – 28: tapered down

pH measurements along Grand Strand, July 23, 2004

RainNo 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: 2 nd Ave N and Springmaid –7/22: 2 nd 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

RainNo RainRain

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) –25 th Ave S Two individual pipes 1222’ 60” diameter Installed June 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?

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