Research Supported in 2016-2018
Funding awarded by the National Sea Grant College Program to S.C. Sea Grant Consortium supported eight peer-reviewed research projects in fiscal years 2016-18. Following are brief summaries of the results of four of those projects.
Sediment samples taken in the Charleston area helped researchers determine the pervasiveness of microplastics in the intertidal zone. Photo provided by The Citadel.
Coastal and Ocean Landscape
How does coastal development impact groundwater inputs to estuarine tidal creeks?
Alicia Wilson, University of South Carolina, and Erik Smith, North Inlet-Winyah Bay National Estuarine Research Reserve/USC Baruch Institute.
The population density of South Carolina’s shoreline counties more than doubled from 1970 to 2010. The area of developed land has been increasing at rates 5-6 times the rate of population growth, with significant development focused at the headwaters of tidal creeks. This raises important questions of whether salt marshes can buffer coastal ecosystems from the impact of development and how groundwater delivery of nutrients to tidal creeks is affected by hydrologic alterations and nutrient additions associated with typical suburban and urban development.
The project assessed the impact of development on groundwater, especially from nitrogen, phosphorous, and carbon, in 15 representative creeks in undeveloped, suburban, and urban areas. Carbon and nitrogen were significantly higher in tidal creeks below undeveloped uplands, while phosphorous was significantly higher in tidal creeks below developed uplands.
Overall project results indicate marshes can buffer the impact of development. Total nutrient concentrations were higher in marsh groundwater than in upland groundwater at all sites, which suggests that salt marshes are a larger source of nutrients than uplands, developed or not.
Sustainable Coastal Development and Economy
Determining sources and impacts of microplastic contamination in coastal South Carolina.
Peter van den Hurk, Clemson University, and John Weinstein, The Citadel.
Plastics pollution of the oceans and coastal zones has been recognized as a major environmental problem. The degradation of large pieces of plastics leads eventually to the proliferation of microplastics, particles that are smaller than 5 millimeters in diameter. This project set out to quantify and identify microplastics in the Charleston harbor area, identify the possible source of these particles, and
establish the potential effects on grass shrimp and mummichogs, an estuarine fish species.
Microplastics were found in the majority (93.5 percent) of intertidal sediments sampled in the Charleston harbor area. Analysis of sediments and water samples demonstrated that blue fibers and black fragments were the most abundant types of microplastics. Further analysis of the black fragments revealed they were tire wear particles which wash down from roads and bridges during rain events.
To evaluate the potential toxicity of these particles, micronized tire fragments were used for tests with grass shrimp and mummichogs. The particles were not directly toxic to the grass shrimp, but they accumulated in their intestines and on their gills, thus forming physical obstructions that might interfere with the normal physiology of these organisms. The mummichog study found that fluorescent chemicals are leaching out of ingested tire fragments and being processed in the liver. These biological effects demonstrate that tire wear particles may be a source of toxic chemicals in the estuarine and coastal environment, and that further research should be conducted to assess the risks for harmful effects on estuarine life.
Safeguarding environmental and public health by developing a tool to rapidly detect cyanobacteria that can cause harmful algal blooms.
Dianne Greenfield, University of South Carolina and S.C. Department of Natural Resources, and Joe Jones, University of South Carolina.
Researchers worked to develop a sandwich hybridization assay (SHA) application for the detection and quantification of harmful algal bloom (HAB) species. SHA is a process to rapidly identify and quantify microscopic organisms using their ribosomal RNA.
The focus for this project was the algae genus Microcystis because these organisms can pose serious regional environmental and public health threats. The SHA was created and tested in a lab, then was used to detect Microcystis during a HAB in a Charleston-area pond in 2016. From a management perspective, this SHA application successfully detects and quantifies Microcystis, making it a valuable tool for water-quality monitoring and HAB management.
Determining sedimentation rates in stormwater detention ponds to improve life-cycle cost assessments associated with maintenance dredging.
Erik Smith, North Inlet-Winyah Bay National Estuarine Research Reserve/USC Baruch Institute, and Claudia Benitez-Nelson, University of South Carolina.
This research was designed to quantify the rate of bulk sediment accumulation across a range of stormwater detention ponds, determine the origin of sediments accumulating in residential ponds, and examine the role residential ponds play in sequestration of carbon, nitrogen, and phosphorus. Fourteen ponds were sampled in urban and suburban Horry and Georgetown counties.
Results suggest stormwater ponds typical of the northern coast of South Carolina have much lower sedimentation rates than anticipated, taking a median of 68 years to reach the 25 percent volume reduction threshold recommended for dredging. This is far longer than the 5 to 10 years anticipated in the state’s guidelines. The major predictor of a pond’s sedimentation rate was the percentage of impervious surfaces, such as roads, parking lots, and buildings, surrounding the pond.
Given previous observations of high algal growth in stormwater detention ponds, internal algal production was anticipated to be the major source of organic matter in pond sediments. However, results showed more evidence of terrestrial plant contribution than algal contribution to organic matter in ponds.
Results also suggest the proliferation of ponds along South Carolina’s coastal zone provides a means for the long-term storage of carbon, nitrogen, and phosphorous, which would otherwise have been transported to coastal waters. Still unclear is whether these rates of sequestration are ecologically significant.