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Long Bay Hypoxia Working Group (continued)
 

(continued)                                                    return to Special Research Programs

“The 2004 hypoxia event was a surprise,” says Denise Sanger, assistant director for research and planning with the S.C. Sea Grant Consortium. “We had not seen this kind of oceanographic dead zone in South Carolina before.”

Map of Long Bay study area
  Map of Long Bay study area

In a series of research projects sponsored by the Consortium, S.C. Department of Health and Environmental Control-Office of Ocean and Coastal Resource Management, and S.C. Department of Natural Resources, scientists are studying physical, biological, chemical, and geological coastal-ocean processes in Long Bay.

South Carolina resource managers and scientists, including Sanger, have assembled a Long Bay Working Group to collaborate on research efforts and understand the causes of the hypoxic event.

It seems that a series of oceanographic conditions in Long Bay (oscillatory wind stress, upwelling, and hot summer weather) in 2004 stratified the water column near the coast, causing the flounder jubilee. Cold water along the ocean bottom was not mixing with warmer surface water, reducing oxygen levels. These conditions, plus the contribution of nutrients in stormwater runoff and groundwater discharge, apparently led to low-oxygen events in Long Bay.

“We have learned a great deal about the Long Bay system,” says Sanger. “In recent years, we have not observed another long-term hypoxic event like the one in 2004. But periodically we are seeing additional low dissolved-oxygen conditions in this environment, and that’s unusual. The levels observed are similar to low dissolved-oxygen that we observe in the naturally stressful, small estuarine headwater creeks. Now we’re finding these conditions in Long Bay just beyond the surf zone, despite strong currents and waves.”

The goal of the S.C. Sea Grant Consortium research effort is to develop tools for future use in forecasting hypoxic events in Long Bay. The research results will be of interest to coastal and fishery managers and local communities.

Consortium researcher George Voulgaris of the University of South Carolina (USC) has developed a high-resolution numerical circulation model for Long Bay. The model is being used to identify the physical scenarios under which low-oxygen events can occur.

In a related study, Eric Koepfler and his colleagues at Coastal Carolina University (CCU) and USC are evaluating the potential and relative roles of marine and terrestrial factors that can affect oxygen levels in Long Bay.

The two studies could provide insights into threshold conditions of future hypoxic events. And they would help identify relative significance of oceanic conditions and human-made sources of nutrients. This information has been identified as critically important by the state’s coastal-zone management program, which funded the first years of these studies.

Moreover, Richard Viso of CCU is conducting research to identify groundwater seep locations along the shelf waters of Long Bay. The information will enable researchers to conduct fieldwork to quantify submarine groundwater discharge, and the contribution of that discharge to water-quality issues, a valuable component to understanding the nutrient fluxes and pollutant transport.

Richard Viso of CCU and a student pump up groundwater from a beachfront area, measuring parameters such as dissolved oxygen and nutrients.
Photo: S.C. Sea Grant Consortium

These research projects have fostered additional efforts, including research by Viso to evaluate the contribution of groundwater discharge to water-quality issues and two pilot studies using autonomous underwater vehicles (AUVs) to validate and expand the findings of Voulgaris and Koepfler.

REMUS AUV device

 

The REMUS AUV was deployed in near-shore waters to collect dissolved oxygen (DO), current speed and direction, temperature, and salinity.
Photo: S.C. Sea Grant Consortium

 

Glider AUV



The Glider AUV, deployed offshore, collected data such as DO, temperature, turbidity, dissolved organic matter, and chlorophyll.
Photo: NOAA Undersea Research Center at University of North Carolina-Wilmington

In addition, the S.C. Department of Natural Resources has funded a study by Susan Libes of CCU to monitor the surface and bottom dissolved-oxygen levels, among other parameters, at Apache Pier on the Grand Strand. This information is providing continuous measurements of the conditions in the area, which researchers have not had in the past.

To learn more about the Long Bay Working Group, contact Denise Sanger, assistant director for research and planning, at denise.sanger@scseagrant.org or (843) 953-2078.


Last updated: 7/1/2009 11:32:27 AM
Long Bay Hypoxia Working Group (continued)

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